eng: Split up requirements engineering chapter

This allows to more easily generate the specification item section with
a script using specification items.

Update #3715.

9 files changed, 1309 insertions, 1283 deletions

diff --git a/eng/index.rst b/eng/index.rst
index a317727..8f91c5e 100644
--- a/eng/index.rst
+++ b/eng/index.rst
@@ -27,7 +27,7 @@ RTEMS Software Engineering (|version|)
     mission
     stakeholders
     prequalification
-    req-eng
+    req/index
     management
     test-plan
     test-framework
diff --git a/eng/req-eng.rst b/eng/req-eng.rst
deleted file mode 100644
index 50b70a8..0000000
--- a/eng/req-eng.rst
+++ /dev/null
@@ -1,1282 +0,0 @@
-.. SPDX-License-Identifier: CC-BY-SA-4.0
-
-.. Copyright (C) 2019, 2020 embedded brains GmbH (http://www.embedded-brains.de)
-
-.. |E40| replace:: ECSS-E-ST-40C
-
-.. |E10-06| replace:: ECSS-E-ST-10-06C
-
-.. _ReqEng:
-
-Software Requirements Engineering
-*********************************
-
-Software engineering standards for critical software such as |E40| demand that
-software requirements for a software product are collected in a software
-requirements specification (technical specification in |E40| terms).  They are
-usually derived from system requirements (requirements baseline in |E40|
-terms).  RTEMS is designed as a reusable software product which can be utilized
-by application designers to ease the development of their applications.  The
-requirements of the end system (system requirements) using RTEMS are only known
-to the application designer.  RTEMS itself is developed by the RTEMS
-maintainers and they do not know the requirements of a particular end system in
-general.  RTEMS is designed as a real-time operating system to meet typical
-system requirements for a wide range of applications.  Its suitability for a
-particular application must be determined by the application designer based on
-the technical specification provided by RTEMS accompanied with performance data
-for a particular target platform.
-
-Currently, no technical specification of RTEMS exists in the form of a
-dedicated document.  Since the beginning of the RTEMS evolution in the late
-1980s it was developed iteratively.  It was never developed in a waterfall
-model.  During initial development the RTEID :cite:`Motorola:1988:RTEID` and
-later the ORKID :cite:`VITA:1990:ORKID` draft specifications were used as
-requirements.  These were evolving during the development and an iterative
-approach was followed often using simple algorithms and coming back to
-optimise.  In 1993 and 1994 a subset of pthreads sufficient to support
-:term:`GNAT` was added as requirements.  At this time the Ada tasking was
-defined, however, not implemented in GNAT, so this involved guessing during the
-development. Later some adjustments were made when Ada tasking was actually
-implemented.  So, it was consciously iterative with the specifications evolving
-and feedback from performance analysis.  Benchmarks published from other real
-time operating systems were used for comparison.  Optimizations were carried
-out until the results were comparable.  Development was done with distinct
-contractual phases and tasks for development, optimization, and the addition of
-priority inheritance and rate monotonic scheduling.  The pthreads requirement
-has grown to be as much POSIX as possible.
-
-Portability from FreeBSD to use its network stack, USB stack, SD/MMC card stack
-and device drivers resulted in another set of requirements.  The addition of
-support for symmetric multiprocessing (SMP) was a huge driver for change.  It
-was developed step by step and sponsored by several independent users with
-completely different applications and target platforms in mind.  The high
-performance OpenMP support introduced the Futex as a new synchronization
-primitive.
-
-.. topic:: Guidance
-
-    A key success element of RTEMS is the ability to accept changes driven by
-    user needs and still keep the operating system stable enough for production
-    systems.  Procedures that place a high burden on changes are doomed to be
-    discarded by the RTEMS Project.  We have to keep this in mind when we
-    introduce a requirements management work flow which should be followed by
-    RTEMS community members and new contributors.
-
-We have to put in some effort first into the reconstruction of software
-requirements through reverse engineering using the RTEMS documentation, test
-cases, sources, standard references, mailing list archives, etc. as input.
-Writing a technical specification for the complete RTEMS code base is probably
-a job of several person-years.  We have to get started with a moderate feature
-set (e.g. subset of the Classic API) and extend it based on user demands step
-by step.
-
-The development of the technical specification will take place in two phases.
-The first phase tries to establish an initial technical specification for an
-initial feature set.  This technical specification will be integrated into
-RTEMS as a big chunk.  In the second phase the technical specification is
-modified through arranged procedures.  There will be procedures
-
-* to modify existing requirements,
-
-* add new requirements, and
-
-* mark requirements as obsolete.
-
-All procedures should be based on a peer review principles.
-
-Requirements for Requirements
-=============================
-
-.. _ReqEngIdent:
-
-Identification
---------------
-
-Each requirement shall have a unique identifier (UID).  The question is in
-which scope should it be unique?  Ideally, it should be universally unique.
-Therefore all UIDs used to link one specification item to another should use
-relative UIDs.  This ensures that the RTEMS requirements can be referenced
-easily in larger systems though a system-specific prefix.  The standard
-ECSS-E-ST-10-06C recommends in section 8.2.6 that the identifier should reflect
-the type of the requirement and the life profile situation.  Other standards
-may have other recommendations.  To avoid a bias of RTEMS in the direction of
-ECSS, this recommendation will not be followed.
-
-The *absolute UID* of a specification item (for example a requirement) is
-defined by a leading ``/`` and the path of directories from the specification
-base directory to the file of the item separated by ``/`` characters and the
-file name without the ``.yml`` extension.  For example, a specification item
-contained in the file :file:`build/cpukit/librtemscpu.yml` inside a
-:file:`spec` directory has the absolute UID of ``/build/cpukit/librtemscpu``.
-
-The *relative UID* to a specification item is defined by the path of
-directories from the file containing the source specification item to the file
-of the destination item separated by ``/`` characters and the file name of the
-destination item without the ``.yml`` extension.  For example the relative UID
-from ``/build/bsps/sparc/leon3/grp`` to ``/build/bsps/bspopts`` is
-``../../bspopts``.
-
-Basically, the valid characters of an UID are determined by the file system
-storing the item files.  By convention, UID characters shall be restricted to
-the following set defined by the regular expression ``[a-zA-Z0-9_-]+``.  Use
-``-`` as a separator inside an UID part.
-
-In documents the URL-like prefix ``spec:`` shall be used to indicated
-specification item UIDs.
-
-The UID scheme for RTEMS requirements shall be component based.  For example,
-the UID ``spec:/classic/task/create-err-invaddr`` may specify that the
-:c:func:`rtems_task_create` directive shall return a status of
-``RTEMS_INVALID_ADDRESS`` if the ``id`` parameter is ``NULL``.
-
-A initial requirement item hierarchy could be this:
-
-* build (building RTEMS BSPs and libraries)
-
-* acfg (application configuration groups)
-
-    * opt (application configuration options)
-
-* classic
-
-    * task
-
-        * create-* (requirements for :c:func:`rtems_task_create`)
-        * delete-* (requirements for :c:func:`rtems_task_delete`)
-        * exit-* (requirements for :c:func:`rtems_task_exit`)
-        * getaff-* (requirements for :c:func:`rtems_task_get_affinity`)
-        * getpri-* (requirements for :c:func:`rtems_task_get_priority`)
-        * getsched-* (requirements for :c:func:`rtems_task_get_scheduler`)
-        * ident-* (requirements for :c:func:`rtems_task_ident`)
-        * issusp-* (requirements for :c:func:`rtems_task_is_suspended`)
-        * iter-* (requirements for :c:func:`rtems_task_iterate`)
-        * mode-* (requirements for :c:func:`rtems_task_mode`)
-        * restart-* (requirements for :c:func:`rtems_task_restart`)
-        * resume* (requirements for :c:func:`rtems_task_resume`)
-        * self* (requirements for :c:func:`rtems_task_self`)
-        * setaff-* (requirements for :c:func:`rtems_task_set_affinity`)
-        * setpri-* (requirements for :c:func:`rtems_task_set_priority`)
-        * setsched* (requirements for :c:func:`rtems_task_set_scheduler`)
-        * start-* (requirements for :c:func:`rtems_task_start`)
-        * susp-* (requirements for :c:func:`rtems_task_suspend`)
-        * wkafter-* (requirements for :c:func:`rtems_task_wake_after`)
-        * wkwhen-* (requirements for :c:func:`rtems_task_wake_when`)
-
-    * sema
-
-        * ...
-
-* posix
-
-* ...
-
-A more detailed naming scheme and guidelines should be established.  We have to
-find the right balance between the length of UIDs and self-descriptive UIDs.  A
-clear scheme for all Classic API managers may help to keep the UIDs short and
-descriptive.
-
-The specification of the validation of requirements should be maintained also
-by specification items.  For each requirement directory there should be a
-validation subdirectory named *test*, e.g. :file:`spec/classic/task/test`.  A
-test specification directory may contain also validations by analysis, by
-inspection, and by design, see :ref:`ReqEngValidation`.
-
-Level of Requirements
----------------------
-
-The level of a requirement shall be expressed with one of the verbal forms
-listed below and nothing else.  The level of requirements are derived from RFC
-2119 :cite:`RFC2119` and |E10-06| :cite:`ECSS_E_ST_10_06C`.
-
-Absolute Requirements
-~~~~~~~~~~~~~~~~~~~~~
-
-Absolute requirements shall be expressed with the verbal form *shall* and no
-other terms.
-
-Absolute Prohibitions
-~~~~~~~~~~~~~~~~~~~~~
-
-Absolute prohibitions shall be expressed with the verbal form *shall not* and
-no other terms.
-
-.. warning::
-
-    Absolute prohibitions may be difficult to validate.  They should not be
-    used.
-
-Recommendations
-~~~~~~~~~~~~~~~
-
-Recommendations shall be expressed with the verbal forms *should* and
-*should not* and no other terms with guidance from RFC 2119:
-
-    SHOULD   This word, or the adjective "RECOMMENDED", mean that there
-    may exist valid reasons in particular circumstances to ignore a
-    particular item, but the full implications must be understood and
-    carefully weighed before choosing a different course.
-
-    SHOULD NOT   This phrase, or the phrase "NOT RECOMMENDED" mean that
-    there may exist valid reasons in particular circumstances when the
-    particular behavior is acceptable or even useful, but the full
-    implications should be understood and the case carefully weighed
-    before implementing any behavior described with this label.
-
-Permissions
-~~~~~~~~~~~
-
-Permissions shall be expressed with the verbal form *may* and no other terms
-with guidance from RFC 2119:
-
-    MAY   This word, or the adjective "OPTIONAL", mean that an item is
-    truly optional.  One vendor may choose to include the item because a
-    particular marketplace requires it or because the vendor feels that
-    it enhances the product while another vendor may omit the same item.
-    An implementation which does not include a particular option MUST be
-    prepared to interoperate with another implementation which does
-    include the option, though perhaps with reduced functionality. In the
-    same vein an implementation which does include a particular option
-    MUST be prepared to interoperate with another implementation which
-    does not include the option (except, of course, for the feature the
-    option provides.)
-
-Possibilities and Capabilities
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-
-Possibilities and capabilities shall be expressed with the verbal form *can*
-and no other terms.
-
-.. _ReqEngSyntax:
-
-Syntax
-------
-
-Use the Easy Approach to Requirements Syntax (:term:`EARS`) to formulate
-requirements.  A recommended reading list to get familiar with this approach is
-:cite:`Mavin:2009:EARS`, :cite:`Mavin:2010:BigEars`, and
-:cite:`Mavin:2016:LLEARS`.  Please also have a look at the EARS quick reference
-sheet :cite:`Uusitalo:2012:EARS`.  The sentence types are:
-
-* Ubiquitous
-
-    The <system name> shall <system response>.
-
-* Event-driven
-
-    *When* <optional preconditions> <trigger>, the <system name> shall <system response>.
-
-* State-driven
-
-    *While* <in state>, the <system name> shall <system response>.
-
-* Unwanted behaviour
-
-    *If* <optional preconditions> <trigger>, *then* the <system name> shall <system response>.
-
-* Optional
-
-    *Where* <feature>, the <system name> shall <system response>.
-
-The optional sentence type should be only used for application configuration
-options.  The goal is to use the *enabled-by* attribute to enable or disable
-requirements based on configuration parameters that define the RTEMS artefacts
-used to build an application executable (header files, libraries, linker command
-files).  Such configuration parameters are for example the architecture, the
-platform, CPU port options, and build configuration options (e.g. uniprocessor
-vs. SMP).
-
-Wording Restrictions
---------------------
-
-To prevent the expression of imprecise requirements, the following terms shall
-not be used in requirement formulations:
-
-* "acceptable"
-* "adequate"
-* "almost always"
-* "and/or"
-* "appropriate"
-* "approximately"
-* "as far as possible"
-* "as much as practicable"
-* "best"
-* "best possible"
-* "easy"
-* "efficient"
-* "e.g."
-* "enable"
-* "enough"
-* "etc."
-* "few"
-* "first rate"
-* "flexible"
-* "generally"
-* "goal"
-* "graceful"
-* "great"
-* "greatest"
-* "ideally"
-* "i.e."
-* "if possible"
-* "in most cases"
-* "large"
-* "many"
-* "maximize"
-* "minimize"
-* "most"
-* "multiple"
-* "necessary"
-* "numerous"
-* "optimize"
-* "ought to"
-* "probably"
-* "quick"
-* "rapid"
-* "reasonably"
-* "relevant"
-* "robust"
-* "satisfactory"
-* "several"
-* "shall be included but not limited to"
-* "simple"
-* "small"
-* "some"
-* "state-of-the-art".
-* "sufficient"
-* "suitable"
-* "support"
-* "systematically"
-* "transparent"
-* "typical"
-* "user-friendly"
-* "usually"
-* "versatile"
-* "when necessary"
-
-For guidelines to avoid these terms see Table 11-2, "Some ambiguous terms to
-avoid in requirements" in :cite:`Wiegers:2013:SR`.  There should be some means
-to enforce that these terms are not used, e.g. through a client-side pre-commit
-Git hook, a server-side pre-receive Git hook, or some scripts run by special
-build commands.
-
-Separate Requirements
----------------------
-
-Requirements shall be stated separately.  A bad example is:
-
-spec:/classic/task/create
-    The task create directive shall evaluate the parameters, allocate a task
-    object and initialize it.
-
-To make this a better example, it should be split into separate requirements:
-
-spec:/classic/task/create
-    When the task create directive is called with valid parameters and a free
-    task object exists, the task create directive shall assign the identifier of
-    an initialized task object to the ``id`` parameter and return the
-    ``RTEMS_SUCCESSFUL`` status.
-
-spec:/classic/task/create-err-toomany
-    If no free task objects exists, the task create directive shall return the
-    ``RTEMS_TOO_MANY`` status.
-
-spec:/classic/task/create-err-invaddr
-    If the ``id`` parameter is ``NULL``, the task create directive shall return the
-    ``RTEMS_INVALID_ADDRESS`` status.
-
-spec:/classic/task/create-err-invname
-    If the ``name`` parameter is invalid, the task create directive shall
-    return the ``RTEMS_INVALID_NAME`` status.
-
-    ...
-
-Conflict Free Requirements
---------------------------
-
-Requirements shall not be in conflict with each other inside a specification.
-A bad example is:
-
-spec:/classic/sema/mtx-obtain-wait
-    When a mutex is not available, the mutex obtain directive shall enqueue the
-    calling thread on the wait queue of the mutex.
-
-spec:/classic/sema/mtx-obtain-err-unsat
-    If a mutex is not available, the mutex obtain directive shall return the
-    RTEMS_UNSATISFIED status.
-
-To resolve this conflict, a condition may be added:
-
-spec:/classic/sema/mtx-obtain-wait
-    When a mutex is not available and the RTEMS_WAIT option is set, the mutex
-    obtain directive shall enqueue the calling thread on the wait queue of the
-    mutex.
-
-spec:/classic/sema/mtx-obtain-err-unsat
-    If a mutex is not available, when the RTEMS_WAIT option is not set, the
-    mutex obtain directive shall return the RTEMS_UNSATISFIED status.
-
-Use of Project-Specific Terms and Abbreviations
------------------------------------------------
-
-All project-specific terms and abbreviations used to formulate requirements
-shall be defined in the project glossary.
-
-.. _ReqEngJustReq:
-
-Justification of Requirements
------------------------------
-
-Each requirement shall have a rationale or justification recorded in a
-dedicated section of the requirement file.  See *rationale* attribute for
-:ref:`ReqEngSpecItems`.
-
-.. _ReqEngSpecItems:
-
-Specification Items
-===================
-
-The technical specification of RTEMS will contain requirements, specializations
-of requirements, :ref:`test procedures <ReqEngTestProcedure>`,
-:ref:`test suites <ReqEngTestSuite>`, :ref:`test cases <ReqEngTestCase>`, and
-:ref:`requirement validations <ReqEngValidation>`.  These things will be called
-*specification items* or just *items* if it is clear from the context.
-
-The specification items are stored in files in :term:`YAML` format with a
-defined set of key-value pairs called attributes.  The key name shall match
-with the pattern defined by the regular expression
-``[a-zA-Z0-9][a-zA-Z0-9-]+``.  In particular, key names which begin with an
-underscore (``_``) are reserved for internal use in tools.
-
-Each specification item shall have the following attributes:
-
-enabled-by
-    The value shall be a list of expressions.  An expression is an operator
-    or an option.  An option evaluates to true if it is included the set of
-    enabled options of the configuration.  An operator is a dictionary with
-    exactly one key and a value.  Valid keys are *and*, *or*, and *not*:
-
-    * The value of the *and* operator shall be a list of expressions.  It
-      evaluates to the *logical and* of all outcomes of the expressions in
-      the list.
-
-    * The value of the *or* operator shall be a list of expressions.  It
-      evaluates to the *logical or* of all outcomes of the expressions in
-      the list.
-
-    * The value of the *not* operator shall be an expression.  It negates
-      the outcome of its expression.
-
-    The outcome of a list of expressions without an operator is the
-    *logical or* of all outcomes of the expressions in the list.  An empty
-    list evaluates to true.  Examples:
-
-    .. code-block:: none
-
-        enabled-by:
-        - RTEMS_SMP
-
-    .. code-block:: none
-
-        enabled-by:
-        - and:
-          - RTEMS_NETWORKING
-          - not: RTEMS_SMP
-
-    .. code-block:: none
-
-        enabled-by:
-        - and:
-          - not: TEST_DEBUGGER01_EXCLUDE
-          - or:
-            - arm
-            - i386
-
-links
-    The value shall be a list of key-value pairs defining links to other
-    specification items.  The list is ordered and defines the order in
-    which links are processed.  There shall be a key *role* with an
-    unspecified value.  There shall be a key *uid* with a relative UID to
-    the item referenced by this link.  Other keys are type-specific.
-    Example:
-
-    .. code-block:: yaml
-
-        links:
-        - role: build-dependency
-          uid: optpwrdwnhlt
-        - role: build-dependency
-          uid: ../../bspopts
-        - role: build-dependency
-          uid: ../start
-
-type
-    The value shall be the specification :ref:`item type <ReqEngItemTypes>`.
-
-The following attributes are used in specification items of various types:
-
-.. _ReqEngItemAttrLicense:
-
-SPDX-License-Identifier
-    The value should be ``BSD-2-Clause OR CC-BY-SA-4.0``.  If content is
-    imported from external sources, then the corresponding license shall be
-    used.  Acceptable licenses are BSD-2-Clause and CC-BY-SA-4.0.  The
-    copyright holder of the external work should be asked to allow a
-    dual-licensing BSD-2-Clause or CC-BY-SA-4.0.  This allows generation of
-    BSD-2-Clause licensed source code and CC-BY-SA-4.0 licensed documentation.
-
-.. _ReqEngItemAttrCopyrights:
-
-copyrights
-    The value shall be a list of copyright statements of the following formats:
-
-    * ``Copyright (C) <YEAR> <COPYRIGHT HOLDER>``
-
-    * ``Copyright (C) <FIRST YEAR>, <LAST YEAR> <COPYRIGHT HOLDER>``
-
-    See also :ref:`FileHeaderCopyright`.
-
-.. _ReqEngItemTypes:
-
-Item Types
-----------
-
-Specification items can have all sorts of *types*.  The selection of types and
-the level of detail depends on a particular standard and product model.  We need
-enough flexibility to be in line with ECSS-E-ST-10-06 and possible future
-applications of other standards.  Each item may have a list of types.  Valid
-types are listed below.  This list may change over time.  If new types are
-added, then a mapping between types should be specified.  The item types and
-their definition is work in progress.  A list of types follows:
-
-* requirement
-
-    * functional - Functional requirements shall describe the behaviour of the
-      software product under specific conditions.
-
-        * *capability*
-
-        * *dependability-function*
-
-        * *function*
-
-        * *operational* - Operational requirements shall
-
-            * define the operation modes (e.g. initialization, multitasking, termination),
-
-            * describe the operation modes, and
-
-            * describe the operation mode transitions.
-
-        * *safety-function*
-
-    * non-functional
-
-        * *build-configuration*
-
-        * *constraint*
-
-        * *design*
-
-        * *interface*
-
-        * *interface-requirement*
-
-        * *maintainability*
-
-        * *performance*
-
-        * *portability*
-
-        * *quality*
-
-        * *reliability*
-
-        * *resource*
-
-        * *safety*
-
-* *test-procedure*
-
-* *test-suite*
-
-* *test-case*
-
-* *validation-by-analysis*
-
-* *validation-by-inspection*
-
-* *validation-by-review-of-design*
-
-* *validation-platform*
-
-.. image:: ../images/eng/req-spec-items.*
-    :scale: 70
-    :align: center
-
-Requirements
-------------
-
-All requirement specification items shall have the following attribute:
-
-rationale:
-    The rationale or justification of the specification item.
-
-Build Configuration
--------------------
-
-Build configuration requirements define what needs to be built (libraries,
-object files, test executables, etc.) and how (configuration option header
-files, compiler flags, linker flags, etc.).  The goal is to generate build
-files (Makefile or waf) and content for the Software Configuration File (SCF)
-from it.  A YAML scheme needs to be defined for this purpose.
-
-.. _ReqEngInterfaceReq:
-
-Interface Requirement
----------------------
-
-Interface requirements shall describe the high level aspects of interfaces.
-The item type shall be *interface-requirement*.
-
-.. _ReqEngInterface:
-
-Interface
----------
-
-.. warning::
-
-    This is work in progress.
-
-Interface items shall specify the interface of the software product to other
-software products and the hardware.  The item type shall be *interface*.  The
-interface items shall have an *interface-category* which is one of the
-following and nothing else:
-
-* *application*: Application interface items shall describe the interface
-  between the software product and the application (:term:`API`).  The goal is
-  to generate header files with Doxygen markup and user manual documentation
-  parts from the application interface specification.
-
-* *application-configuration*: Application configuration items shall define
-  parameters of the software product which can be set by the application at
-  link-time.  The goal is to generate user manual documentation parts and test
-  cases from the application configuration specification.
-
-* *architecture*: Architecture interface items shall define the
-  interface between the software product and the processor architecture
-  (:term:`ABI`).
-
-* *gcc*: GCC interface items shall define the interface between the software
-  product and GCC components such as libgcc.a, libatomic.a, libgomp.a,
-  libstdc++.a, etc.
-
-* *hardware*: Hardware interface items shall define the interface between the
-  software product and the hardware.
-
-* *newlib*: Newlib interface items shall define the interface between the
-  software product and the Newlib (libc.a).
-
-The interface items shall have an *interface-type* which is one of the
-following and nothing else:
-
-* *configuration-option*
-
-* *define*
-
-* *enum*
-
-* *function*
-
-* *header*
-
-* *macro*
-
-* *register-block*
-
-* *structure*
-
-* *typedef*
-
-* *union*
-
-* *variable*
-
-.. _ReqEngInterfaceApplicationConfigGroups:
-
-Interface - Application Configuration Groups
---------------------------------------------
-
-The application configuration group items shall have the following attribute
-specializations:
-
-SPDX-License-Identifier
-    See :ref:`SPDX-License-Identifier <ReqEngItemAttrLicense>`.
-
-appl-config-group-description:
-    The value shall be the description of this application configuration group.
-
-appl-config-group-name:
-    The value shall be the name of this application configuration group.
-
-copyrights
-    See :ref:`copyrights <ReqEngItemAttrCopyrights>`.
-
-interface-type
-    The interface type value shall be *appl-config-group*.
-
-link
-    There shall be a link to a higher level requirement.
-
-text
-    The application configuration group requirement.
-
-type
-    The type value shall be *interface*.
-
-.. _ReqEngInterfaceApplicationConfigOptions:
-
-Interface - Application Configuration Options
----------------------------------------------
-
-The application configuration option items shall have the following attribute
-specializations:
-
-SPDX-License-Identifier
-    See :ref:`SPDX-License-Identifier <ReqEngItemAttrLicense>`.
-
-appl-config-option-constraint
-    This attribute shall be present only for *initializer* and *integer*
-    type options.  The value shall be a dictionary of the following optional
-    key-value pairs.
-
-    custom
-        The value shall be a list of constraints in natural language.  Use the
-        following wording:
-
-            The value of this configuration option shall be ...
-
-    min
-        The value shall be the minimum value of the option.
-
-    max
-        The value shall be the maximum value of the option.
-
-    links
-        The value shall be a list of relative UIDs to constraints.
-
-    set
-        The value shall be the list of valid values of the option.
-
-appl-config-option-default
-    This attribute shall be present only for *feature* type options.  The value
-    shall be a description of the default configuration in case this boolean
-    feature define is undefined.  Use the following wording:
-
-        If this configuration option is undefined, then ...
-
-appl-config-option-default-value
-    This attribute shall be present only for *initializer* and *integer*
-    type options.  The value shall be an initializer, an integer, or a
-    descriptive text.
-
-appl-config-option-description
-    For *feature* and *feature-enable* type options, the value shall be a
-    description of the configuration in case this boolean feature define is
-    defined.  Use the following wording:
-
-        In case this configuration option is defined, then ...
-
-    For *initializer* and *integer* options, the value shall describe the
-    effect of the option value.  The description should focus on the average
-    use-case.  It should not cover potential problems, constraints, obscure
-    use-cases, corner cases and everything which makes matters complicated.
-    Add these things to *appl-config-option-constraint* and
-    *appl-config-option-notes*.  Use the following wording:
-
-        The value of this configuration option defines ...
-
-appl-config-option-index
-    The value shall be a list of entries for the document index.  By default,
-    the application configuration option name is added to the index.
-
-appl-config-option-name
-    The value shall be the name of the application configuration option.  Use a
-    pattern of ``CONFIGURE_[A-Z0-9_]+`` for the name.
-
-appl-config-option-notes
-    The value shall be the notes for this option.  The notes should explain
-    everything which was omitted from the description.  It should cover all the
-    details, special cases, usage notes, error conditions, configuration
-    dependencies, and references.
-
-appl-config-option-type
-    The value shall be one of the following and nothing else:
-
-    feature
-        Use this type for boolean feature opions which have a behaviour in the
-        default configuration which is not just that the feature is disabled.
-
-    feature-enable
-        Use this type for boolean feature opions which just enables a feature.
-
-    initializer
-        Use this type for options which initialize a data structure.
-
-    integer
-        Use this type for integer options.
-
-copyrights
-    See :ref:`copyrights <ReqEngItemAttrCopyrights>`.
-
-interface-type
-    The interface type value shall be *appl-config-option*.
-
-link
-    There shall be a link to the application configuration group to which this
-    option belongs.
-
-text
-    The application configuration option requirement.
-
-type
-    The type value shall be *interface*.
-
-.. _ReqEngTestProcedure:
-
-Test Procedure
---------------
-
-Test procedures shall be executed by the Qualification Toolchain.
-
-The test procedure items shall have the following attribute
-specializations:
-
-type
-    The type value shall be *test-procedure*.
-
-text
-    The purpose of this test procedure.
-
-platform
-    There shall be links to validation platform requirements.
-
-steps
-    The test procedure steps.  Could be a list of key-value pairs.  The key
-    is the step name and the value is a description of the actions
-    performed in this step.
-
-.. _ReqEngTestSuite:
-
-Test Suite
-----------
-
-Test suites shall use the :ref:`RTEMS Test Framework <RTEMSTestFramework>`.
-
-The test suite items shall have the following attribute specializations:
-
-type
-    The type value shall be *test-suite*.
-
-text
-    The test suite description.
-
-.. _ReqEngTestCase:
-
-Test Case
----------
-
-Test cases shall use the :ref:`RTEMS Test Framework <RTEMSTestFramework>`.
-
-The test case items shall have the following attribute specializations:
-
-type
-    The type value shall be *test-case*.
-
-link
-    The link to the requirement validated by this test case or no links if
-    this is a unit or integration test case.
-
-ref
-    If this is a unit test case, then a reference to the :term:`software
-    item` under test shall be provided.  If this is an integration test
-    case, then a reference to the integration under test shall be provided.
-    The integration is identified by its Doxygen group name.
-
-text
-    A short description of the test case.
-
-inputs
-    The inputs to execute the test case.
-
-outputs
-    The expected outputs.
-
-The test case code may be also contained in the test case specification
-item in a *code* attribute.  This is subject to discussion on the RTEMS
-mailing list.  Alternatively, the test code could be placed directly in
-source files.  A method is required to find the test case specification of
-a test case code and vice versa.
-
-.. _ReqEngResAndPerf:
-
-Resources and Performance
--------------------------
-
-Normally, resource and performance requirements are formulated like this:
-
-* The resource U shall need less than V storage units.
-
-* The operation Y shall complete within X time units.
-
-Such statements are difficult to make for a software product like RTEMS which
-runs on many different target platforms in various configurations.  So, the
-performance requirements of RTEMS shall be stated in terms of benchmarks.  The
-benchmarks are run on the project-specific target platform and configuration.
-The results obtained by the benchmark runs are reported in a human readable
-presentation.  The application designer can then use the benchmark results to
-determine if its system performance requirements are met.  The benchmarks shall
-be executed under different environment conditions, e.g. varying cache states
-(dirty, empty, valid) and system bus load generated by other processors.  The
-application designer shall have the ability to add additional environment
-conditions, e.g. system bus load by DMA engines or different system bus
-arbitration schemes.
-
-To catch resource and performance regressions via test suite runs there shall be
-a means to specify threshold values for the measured quantities.  The threshold
-values should be provided for each validation platform.  How this can be done
-and if the threshold values are maintained by the RTEMS Project is subject to
-discussion.
-
-.. _ReqEngTrace:
-
-Traceability of Specification Items
-===================================
-
-The standard |E10-06| demands that requirements shall be under configuration
-management, backwards-traceable and forward-traceable.  Requirements are a
-specialization of specification items in RTEMS.
-
-.. _ReqEngTraceHistory:
-
-History of Specification Items
-------------------------------
-
-The RTEMS specification items should placed in the RTEMS sources using Git for
-version control.  The history of specification items can be traced with Git.
-Special commit procedures for changes in specification item files should be
-established.  For example, it should be allowed to change only one
-specification item per commit.  A dedicated Git commit message format may be
-used as well, e.g. use of ``Approved-by:`` or ``Reviewed-by:`` lines which
-indicate an agreed statement (similar to the
-`Linux kernel patch submission guidelines <https://www.kernel.org/doc/html/latest//process/submitting-patches.html#using-reported-by-tested-by-reviewed-by-suggested-by-and-fixes>`_).
-Git commit procedures may be ensured through a server-side pre-receive hook.
-The history of requirements may be also added to the specification items
-directly in a *revision* attribute.  This would make it possible to generate
-the history information for documents without having the Git repository
-available, e.g. from an RTEMS source release archive.
-
-.. _ReqEngTraceBackward:
-
-Backward Traceability of Specification Items
---------------------------------------------
-
-Providing backward traceability of specification items means that we must be
-able to find the corresponding higher level specification item for each refined
-specification item.  A custom tool needs to verify this.
-
-.. _ReqEngTraceForward:
-
-Forward Traceability of Specification Items
--------------------------------------------
-
-Providing forward traceability of specification items means that we must be
-able to find all the refined specification items for each higher level
-specification item.  A custom tool needs to verify this.  The links from
-parent to child specification items are implicitly defined by links from a
-child item to a parent item.
-
-.. _ReqEngTraceReqArchDesign:
-
-Traceability between Software Requirements, Architecture and Design
--------------------------------------------------------------------
-
-The software requirements are implemented in custom YAML files, see
-:ref:`ReqEngSpecItems`.  The software architecture and design is written in
-Doxygen markup.  Doxygen markup is used throughout all header and source files.
-A Doxygen filter program may be provided to place Doxygen markup in assembler
-files.  The software architecture is documented via Doxygen groups.  Each
-Doxygen group name should have a project-specific name and the name should be
-unique within the project, e.g.  RTEMSTopLevel\ MidLevel\ LowLevel.  The link
-from a Doxygen group to its parent group is realized through the ``@ingroup``
-special command.  The link from a Doxygen group or :term:`software component`
-to the corresponding requirement is realized through a ``@satisfy{req}``
-`custom command <http://www.doxygen.nl/manual/custcmd.html>`_ which needs the
-identifier of the requirement as its one and only parameter.  Only links to
-parents are explicitly given in the Doxygen markup.  The links from a parent to
-its children are only implicitly specified via the link from a child to its
-parent.  So, a tool must process all files to get the complete hierarchy of
-software requirements, architecture and design. Links from a software component
-to another software component are realized through automatic Doxygen references
-or the ``@ref`` and ``@see`` special commands.
-
-.. _ReqEngValidation:
-
-Requirement Validation
-======================
-
-The validation of each requirement shall be accomplished by one or more of
-the following methods and nothing else:
-
-* *By test*: A :ref:`ReqEngTestCase` specification item is provided to
-  demonstrate that the requirement is satisfied when the software product is
-  executed on the target platform.
-
-* *By analysis*: A statement is provided how the requirement is met, by
-  analysing static properties of the software product.
-
-* *By inspection*: A statement is provided how the requirement is met, by
-  inspection of the :term:`source code`.
-
-* *By review of design*: A rationale is provided to demonstrate how the
-  qualification requirement is satisfied implicitly by the software design.
-
-Validation by test is strongly recommended.  The choice of any other validation
-method shall be strongly justified.  The requirements author is obligated to
-provide the means to validate the requirement with detailed instructions.
-
-For a specification item in a parent directory it could be checked that at
-least one item in a subdirectory has a link to it.  For example a subdirectory
-could contain validation items.  With this feature you could check that all
-requirements are covered by at least one validation item.
-
-The requirement validation by analysis, by inspection, and by design
-specification items shall have the following attribute specializations:
-
-type
-    The type attribute value shall be *validation-by-analysis*,
-    *validation-by-inspection*, or *validation-by-review-of-design*.
-
-link
-    There shall be exactly one link to the validated requirement.
-
-text
-    The statement or rational of the requirement validation.
-
-Requirement Management
-======================
-
-Change Control Board
---------------------
-
-Working with requirements usually involves a Change Control Board
-(:term:`CCB`).  The CCB of the RTEMS Project is the
-`RTEMS developer mailing list <https://lists.rtems.org/mailman/listinfo/devel>`_.
-
-There are the following actors involved:
-
-* *RTEMS users*: Everyone using the RTEMS real-time operating system to design,
-  develop and build an application on top of it.
-
-* *RTEMS developers*: The persons developing and maintaining RTEMS.  They write
-  patches to add or modify code, requirements, tests and documentation.
-
-* *RTEMS maintainers*: They are listed in the
-  `MAINTAINERS <https://git.rtems.org/rtems/tree/MAINTAINERS>`_ file and have
-  write access to the project repositories.
-
-Adding and changing requirements follows the normal patch review process.  The
-normal patch review process is described in the
-`RTEMS User Manual <https://docs.rtems.org/branches/master/user/support/contrib.html#patch-review-process>`_.
-Reviews and comments may be submitted by anyone, but a maintainer review is
-required to approve *significant* changes.  In addition for significant
-changes, there should be at least one reviewer with a sufficient independence
-from the author which proposes a new requirement or a change of an existing
-requirement.  Working in another company on different projects is sufficiently
-independent.  RTEMS maintainers do not know all the details, so they trust in
-general people with experience on a certain platform.  Sometimes no review
-comments may appear in a reasonable time frame, then an implicit agreement to
-the proposed changes is assumed.  Patches can be sent at anytime, so
-controlling changes in RTEMS requires a permanent involvement on the RTEMS
-developer mailing list.
-
-For a qualification of RTEMS according to certain standards, the requirements
-may be approved by an RTEMS user.  The approval by RTEMS users is not the
-concern of the RTEMS Project, however, the RTEMS Project should enable RTEMS
-users to manage the approval of requirements easily.  This information may be
-also used by a independent authority which comes into play with an Independent
-Software Verification and Validation (:term:`ISVV`).  It could be used to
-select a subset of requirements, e.g. look only at the ones approved by a
-certain user.  RTEMS users should be able to reference the determinative
-content of requirements, test procedures, test cases and justification reports
-in their own documentation.  Changes in the determinative content should
-invalidate all references to previous versions.
-
-Add a Requirement
------------------
-
-.. image:: ../images/eng/req-add.*
-    :scale: 70
-    :align: center
-
-.. _ReqEngModifyRequirement:
-
-Modify a Requirement
---------------------
-
-.. image:: ../images/eng/req-modify.*
-    :scale: 70
-    :align: center
-
-Mark a Requirement as Obsolete
-------------------------------
-
-Requirements shall be never removed.  They shall be marked as obsolete.  This
-ensures that requirement identifiers are not reused.  The procedure to obsolete
-a requirement is the same as the one to :ref:`modify a requirement
-<ReqEngModifyRequirement>`.
-
-Tooling
-=======
-
-Tool Requirements
------------------
-
-To manage requirements some tool support is helpful.  Here is a list of
-requirements for the tool:
-
-* The tool shall be open source.
-
-* The tool should be actively maintained during the initial phase of the RTEMS
-  requirements specification.
-
-* The tool shall use plain text storage (no binary formats, no database).
-
-* The tool shall support version control via Git.
-
-* The tool should export the requirements in a human readable form using the
-  Sphinx documentation framework.
-
-* The tool shall support traceability of requirements to items external to the
-  tool.
-
-* The tool shall support traceability between requirements.
-
-* The tool shall support custom requirement attributes.
-
-* The tool should ensure that there are no cyclic dependencies between
-  requirements.
-
-* The tool should provide an export to :term:`ReqIF`.
-
-Tool Evaluation
----------------
-
-During an evaluation phase the following tools were considered:
-
-* `aNimble <https://sourceforge.net/projects/nimble/>`_
-* :term:`Doorstop`
-* `OSRMT <https://github.com/osrmt/osrmt>`_
-* `Papyrus <https://www.eclipse.org/papyrus/>`_
-* `ProR <https://www.eclipse.org/rmf/pror/>`_
-* `ReqIF Studio <https://formalmind.com/tools/studio/>`_
-* `Requirement Heap <https://sourceforge.net/projects/reqheap/>`_
-* `rmToo <http://rmtoo.florath.net/>`_
-
-The tools aNimble, OSRMT and Requirement Heap were not selected since they use
-a database.  The tools Papyrus, ProR and ReqIF are Eclipse based and use
-complex XML files for data storage.  They were difficult to use and lack good
-documentation/tutorials.  The tools rmToo and Doorstop turned out to be the
-best candidates to manage requirements in the RTEMS Project.  The Doorstop tool
-was selected as the first candidate mainly due a recommendation by an RTEMS
-user.
-
-.. _ReqEngDoorstop:
-
-Best Available Tool - Doorstop
-------------------------------
-
-:term:`Doorstop` is a requirements management tool.  It has a modern,
-object-oriented and well-structured implementation in Python 3.6 under the
-LGPLv3 license.  It uses a continuous integration build with style checkers,
-static analysis, documentation checks, code coverage, unit test and integration
-tests.  In 2019, the project was actively maintained.  Pull requests for minor
-improvements and new features were reviewed and integrated within days.  Each
-requirement is contained in a single file in :term:`YAML` format.  Requirements
-are organized in documents and can be linked to each other
-:cite:`Browning:2014:RequirementsManagement`.
-
-Doorstop consists of three main parts
-
-* a stateless command line tool `doorstop`,
-
-* a file format with a pre-defined set of attributes (YAML), and
-
-* a primitive GUI tool (not intended to be used).
-
-For RTEMS, its scope will be extended to manage specifications in general.  The
-primary reason for selecting Doorstop as the requirements management tool for
-the RTEMS Project is its data format which allows a high degree of
-customization.  Doorstop uses a directed, acyclic graph (DAG) of items.  The
-items are files in YAML format.  Each item has a set of
-`standard attributes <https://doorstop.readthedocs.io/en/latest/reference/item/>`_
-(key-value pairs).
-
-The use case for the standard attributes is requirements management.  However,
-Doorstop is capable to manage custom attributes as well.  We will heavily use
-custom attributes for the specification items.  Enabling Doorstop to effectively
-use custom attributes was done specifically for the RTEMS Project in several
-patch sets.
-
-A key feature of Doorstop is the `fingerprint of items
-<https://doorstop.readthedocs.io/en/latest/reference/item/#reviewed>`_.
-For the RTEMS Project, the fingerprint hash algorithm was changed from MD5 to
-SHA256.  In 2019, it can be considered cryptographically secure.  The
-fingerprint should cover the normative values of an item, e.g. comments etc. are
-not included.  The fingerprint helps RTEMS users to track the significant
-changes in the requirements (in contrast to all the changes visible in Git).  As
-an example use case, a user may want to assign a project-specific status to
-specification items.  This can be done with a table which contains columns for 
-
-1. the UID of the item,
-
-2. the fingerprint, and
-
-3. the project-specific status.
-
-Given the source code of RTEMS (which includes the specification items) and this
-table, it can be determined which items are unchanged and which have another
-status (e.g. unknown, changed, etc.).
-
-After some initial work with Doorstop some issues surfaced
-(`#471 <https://github.com/doorstop-dev/doorstop/issues/471>`_)
-It turned out that Doorstop is not designed as a library and contains to much
-policy. This results in a lack of flexibility required for the RTEMS Project.
-
-1. Its primary use case is requirements management. So, it has some standard
-   attributes useful in this domain, like derived, header, level, normative,
-   ref, reviewed, and text. However, we want to use it more generally for
-   specification items and these attributes make not always sense.  Having them
-   in every item is just overhead and may cause confusion.
-
-2. The links cannot have custom attributes, e.g. role, enabled-by. With
-   link-specific attributes you could have multiple DAGs formed up by the same
-   set of items.
-
-3. Inside a document (directory) items are supposed to have a common type (set
-   of attributes). We would like to store at a hierarchy level also distinct
-   specializations.
-
-4. The verification of the items is quite limited.  We need verification with
-   type-based rules.
-
-5. The UIDs in combination with the document hierarchy lead to duplication,
-   e.g. a/b/c/a-b-c-d.yml. You have the path (a/b/c) also in the file name
-   (a-b-c). You cannot have relative UIDs in links (e.g. ../parent-req) . The
-   specification items may contain multiple requirements, e.g. min/max
-   attributes.  There is no way to identify them.
-
-6. The links are ordered by Doorstop alphabetically by UID. For some
-   applications, it would be better to use the order specified by the user. For
-   example, we want to use specification items for a new build system. Here it
-   is handy if you can express things like this: A is composed of B and C.
-   Build B before C.
diff --git a/eng/req/index.rst b/eng/req/index.rst
new file mode 100644
index 0000000..b793130
--- /dev/null
+++ b/eng/req/index.rst
@@ -0,0 +1,92 @@
+.. SPDX-License-Identifier: CC-BY-SA-4.0
+
+.. Copyright (C) 2019, 2020 embedded brains GmbH (http://www.embedded-brains.de)
+
+.. |E40| replace:: ECSS-E-ST-40C
+
+.. _ReqEng:
+
+Software Requirements Engineering
+*********************************
+
+Software engineering standards for critical software such as |E40| demand that
+software requirements for a software product are collected in a software
+requirements specification (technical specification in |E40| terms).  They are
+usually derived from system requirements (requirements baseline in |E40|
+terms).  RTEMS is designed as a reusable software product which can be utilized
+by application designers to ease the development of their applications.  The
+requirements of the end system (system requirements) using RTEMS are only known
+to the application designer.  RTEMS itself is developed by the RTEMS
+maintainers and they do not know the requirements of a particular end system in
+general.  RTEMS is designed as a real-time operating system to meet typical
+system requirements for a wide range of applications.  Its suitability for a
+particular application must be determined by the application designer based on
+the technical specification provided by RTEMS accompanied with performance data
+for a particular target platform.
+
+Currently, no technical specification of RTEMS exists in the form of a
+dedicated document.  Since the beginning of the RTEMS evolution in the late
+1980s it was developed iteratively.  It was never developed in a waterfall
+model.  During initial development the RTEID :cite:`Motorola:1988:RTEID` and
+later the ORKID :cite:`VITA:1990:ORKID` draft specifications were used as
+requirements.  These were evolving during the development and an iterative
+approach was followed often using simple algorithms and coming back to
+optimise.  In 1993 and 1994 a subset of pthreads sufficient to support
+:term:`GNAT` was added as requirements.  At this time the Ada tasking was
+defined, however, not implemented in GNAT, so this involved guessing during the
+development. Later some adjustments were made when Ada tasking was actually
+implemented.  So, it was consciously iterative with the specifications evolving
+and feedback from performance analysis.  Benchmarks published from other real
+time operating systems were used for comparison.  Optimizations were carried
+out until the results were comparable.  Development was done with distinct
+contractual phases and tasks for development, optimization, and the addition of
+priority inheritance and rate monotonic scheduling.  The pthreads requirement
+has grown to be as much POSIX as possible.
+
+Portability from FreeBSD to use its network stack, USB stack, SD/MMC card stack
+and device drivers resulted in another set of requirements.  The addition of
+support for symmetric multiprocessing (SMP) was a huge driver for change.  It
+was developed step by step and sponsored by several independent users with
+completely different applications and target platforms in mind.  The high
+performance OpenMP support introduced the Futex as a new synchronization
+primitive.
+
+.. topic:: Guidance
+
+    A key success element of RTEMS is the ability to accept changes driven by
+    user needs and still keep the operating system stable enough for production
+    systems.  Procedures that place a high burden on changes are doomed to be
+    discarded by the RTEMS Project.  We have to keep this in mind when we
+    introduce a requirements management work flow which should be followed by
+    RTEMS community members and new contributors.
+
+We have to put in some effort first into the reconstruction of software
+requirements through reverse engineering using the RTEMS documentation, test
+cases, sources, standard references, mailing list archives, etc. as input.
+Writing a technical specification for the complete RTEMS code base is probably
+a job of several person-years.  We have to get started with a moderate feature
+set (e.g. subset of the Classic API) and extend it based on user demands step
+by step.
+
+The development of the technical specification will take place in two phases.
+The first phase tries to establish an initial technical specification for an
+initial feature set.  This technical specification will be integrated into
+RTEMS as a big chunk.  In the second phase the technical specification is
+modified through arranged procedures.  There will be procedures
+
+* to modify existing requirements,
+
+* add new requirements, and
+
+* mark requirements as obsolete.
+
+All procedures should be based on a peer review principles.
+
+.. toctree::
+
+    req-for-req
+    items
+    validation
+    traceability
+    management
+    tooling
diff --git a/eng/req/items.rst b/eng/req/items.rst
new file mode 100644
index 0000000..0c13bb2
--- /dev/null
+++ b/eng/req/items.rst
@@ -0,0 +1,520 @@
+.. SPDX-License-Identifier: CC-BY-SA-4.0
+
+.. Copyright (C) 2019, 2020 embedded brains GmbH (http://www.embedded-brains.de)
+
+.. _ReqEngSpecItems:
+
+Specification Items
+===================
+
+The technical specification of RTEMS will contain requirements, specializations
+of requirements, :ref:`test procedures <ReqEngTestProcedure>`,
+:ref:`test suites <ReqEngTestSuite>`, :ref:`test cases <ReqEngTestCase>`, and
+:ref:`requirement validations <ReqEngValidation>`.  These things will be called
+*specification items* or just *items* if it is clear from the context.
+
+The specification items are stored in files in :term:`YAML` format with a
+defined set of key-value pairs called attributes.  The key name shall match
+with the pattern defined by the regular expression
+``[a-zA-Z0-9][a-zA-Z0-9-]+``.  In particular, key names which begin with an
+underscore (``_``) are reserved for internal use in tools.
+
+Each specification item shall have the following attributes:
+
+enabled-by
+    The value shall be a list of expressions.  An expression is an operator
+    or an option.  An option evaluates to true if it is included the set of
+    enabled options of the configuration.  An operator is a dictionary with
+    exactly one key and a value.  Valid keys are *and*, *or*, and *not*:
+
+    * The value of the *and* operator shall be a list of expressions.  It
+      evaluates to the *logical and* of all outcomes of the expressions in
+      the list.
+
+    * The value of the *or* operator shall be a list of expressions.  It
+      evaluates to the *logical or* of all outcomes of the expressions in
+      the list.
+
+    * The value of the *not* operator shall be an expression.  It negates
+      the outcome of its expression.
+
+    The outcome of a list of expressions without an operator is the
+    *logical or* of all outcomes of the expressions in the list.  An empty
+    list evaluates to true.  Examples:
+
+    .. code-block:: none
+
+        enabled-by:
+        - RTEMS_SMP
+
+    .. code-block:: none
+
+        enabled-by:
+        - and:
+          - RTEMS_NETWORKING
+          - not: RTEMS_SMP
+
+    .. code-block:: none
+
+        enabled-by:
+        - and:
+          - not: TEST_DEBUGGER01_EXCLUDE
+          - or:
+            - arm
+            - i386
+
+links
+    The value shall be a list of key-value pairs defining links to other
+    specification items.  The list is ordered and defines the order in
+    which links are processed.  There shall be a key *role* with an
+    unspecified value.  There shall be a key *uid* with a relative UID to
+    the item referenced by this link.  Other keys are type-specific.
+    Example:
+
+    .. code-block:: yaml
+
+        links:
+        - role: build-dependency
+          uid: optpwrdwnhlt
+        - role: build-dependency
+          uid: ../../bspopts
+        - role: build-dependency
+          uid: ../start
+
+type
+    The value shall be the specification :ref:`item type <ReqEngItemTypes>`.
+
+The following attributes are used in specification items of various types:
+
+.. _ReqEngItemAttrLicense:
+
+SPDX-License-Identifier
+    The value should be ``BSD-2-Clause OR CC-BY-SA-4.0``.  If content is
+    imported from external sources, then the corresponding license shall be
+    used.  Acceptable licenses are BSD-2-Clause and CC-BY-SA-4.0.  The
+    copyright holder of the external work should be asked to allow a
+    dual-licensing BSD-2-Clause or CC-BY-SA-4.0.  This allows generation of
+    BSD-2-Clause licensed source code and CC-BY-SA-4.0 licensed documentation.
+
+.. _ReqEngItemAttrCopyrights:
+
+copyrights
+    The value shall be a list of copyright statements of the following formats:
+
+    * ``Copyright (C) <YEAR> <COPYRIGHT HOLDER>``
+
+    * ``Copyright (C) <FIRST YEAR>, <LAST YEAR> <COPYRIGHT HOLDER>``
+
+    See also :ref:`FileHeaderCopyright`.
+
+.. _ReqEngItemTypes:
+
+Item Types
+----------
+
+Specification items can have all sorts of *types*.  The selection of types and
+the level of detail depends on a particular standard and product model.  We need
+enough flexibility to be in line with ECSS-E-ST-10-06 and possible future
+applications of other standards.  Each item may have a list of types.  Valid
+types are listed below.  This list may change over time.  If new types are
+added, then a mapping between types should be specified.  The item types and
+their definition is work in progress.  A list of types follows:
+
+* requirement
+
+    * functional - Functional requirements shall describe the behaviour of the
+      software product under specific conditions.
+
+        * *capability*
+
+        * *dependability-function*
+
+        * *function*
+
+        * *operational* - Operational requirements shall
+
+            * define the operation modes (e.g. initialization, multitasking, termination),
+
+            * describe the operation modes, and
+
+            * describe the operation mode transitions.
+
+        * *safety-function*
+
+    * non-functional
+
+        * *build-configuration*
+
+        * *constraint*
+
+        * *design*
+
+        * *interface*
+
+        * *interface-requirement*
+
+        * *maintainability*
+
+        * *performance*
+
+        * *portability*
+
+        * *quality*
+
+        * *reliability*
+
+        * *resource*
+
+        * *safety*
+
+* *test-procedure*
+
+* *test-suite*
+
+* *test-case*
+
+* *validation-by-analysis*
+
+* *validation-by-inspection*
+
+* *validation-by-review-of-design*
+
+* *validation-platform*
+
+.. image:: ../../images/eng/req-spec-items.*
+    :scale: 70
+    :align: center
+
+Requirements
+------------
+
+All requirement specification items shall have the following attribute:
+
+rationale:
+    The rationale or justification of the specification item.
+
+Build Configuration
+-------------------
+
+Build configuration requirements define what needs to be built (libraries,
+object files, test executables, etc.) and how (configuration option header
+files, compiler flags, linker flags, etc.).  The goal is to generate build
+files (Makefile or waf) and content for the Software Configuration File (SCF)
+from it.  A YAML scheme needs to be defined for this purpose.
+
+.. _ReqEngInterfaceReq:
+
+Interface Requirement
+---------------------
+
+Interface requirements shall describe the high level aspects of interfaces.
+The item type shall be *interface-requirement*.
+
+.. _ReqEngInterface:
+
+Interface
+---------
+
+.. warning::
+
+    This is work in progress.
+
+Interface items shall specify the interface of the software product to other
+software products and the hardware.  The item type shall be *interface*.  The
+interface items shall have an *interface-category* which is one of the
+following and nothing else:
+
+* *application*: Application interface items shall describe the interface
+  between the software product and the application (:term:`API`).  The goal is
+  to generate header files with Doxygen markup and user manual documentation
+  parts from the application interface specification.
+
+* *application-configuration*: Application configuration items shall define
+  parameters of the software product which can be set by the application at
+  link-time.  The goal is to generate user manual documentation parts and test
+  cases from the application configuration specification.
+
+* *architecture*: Architecture interface items shall define the
+  interface between the software product and the processor architecture
+  (:term:`ABI`).
+
+* *gcc*: GCC interface items shall define the interface between the software
+  product and GCC components such as libgcc.a, libatomic.a, libgomp.a,
+  libstdc++.a, etc.
+
+* *hardware*: Hardware interface items shall define the interface between the
+  software product and the hardware.
+
+* *newlib*: Newlib interface items shall define the interface between the
+  software product and the Newlib (libc.a).
+
+The interface items shall have an *interface-type* which is one of the
+following and nothing else:
+
+* *configuration-option*
+
+* *define*
+
+* *enum*
+
+* *function*
+
+* *header*
+
+* *macro*
+
+* *register-block*
+
+* *structure*
+
+* *typedef*
+
+* *union*
+
+* *variable*
+
+.. _ReqEngInterfaceApplicationConfigGroups:
+
+Interface - Application Configuration Groups
+--------------------------------------------
+
+The application configuration group items shall have the following attribute
+specializations:
+
+SPDX-License-Identifier
+    See :ref:`SPDX-License-Identifier <ReqEngItemAttrLicense>`.
+
+appl-config-group-description:
+    The value shall be the description of this application configuration group.
+
+appl-config-group-name:
+    The value shall be the name of this application configuration group.
+
+copyrights
+    See :ref:`copyrights <ReqEngItemAttrCopyrights>`.
+
+interface-type
+    The interface type value shall be *appl-config-group*.
+
+link
+    There shall be a link to a higher level requirement.
+
+text
+    The application configuration group requirement.
+
+type
+    The type value shall be *interface*.
+
+.. _ReqEngInterfaceApplicationConfigOptions:
+
+Interface - Application Configuration Options
+---------------------------------------------
+
+The application configuration option items shall have the following attribute
+specializations:
+
+SPDX-License-Identifier
+    See :ref:`SPDX-License-Identifier <ReqEngItemAttrLicense>`.
+
+appl-config-option-constraint
+    This attribute shall be present only for *initializer* and *integer*
+    type options.  The value shall be a dictionary of the following optional
+    key-value pairs.
+
+    custom
+        The value shall be a list of constraints in natural language.  Use the
+        following wording:
+
+            The value of this configuration option shall be ...
+
+    min
+        The value shall be the minimum value of the option.
+
+    max
+        The value shall be the maximum value of the option.
+
+    links
+        The value shall be a list of relative UIDs to constraints.
+
+    set
+        The value shall be the list of valid values of the option.
+
+appl-config-option-default
+    This attribute shall be present only for *feature* type options.  The value
+    shall be a description of the default configuration in case this boolean
+    feature define is undefined.  Use the following wording:
+
+        If this configuration option is undefined, then ...
+
+appl-config-option-default-value
+    This attribute shall be present only for *initializer* and *integer*
+    type options.  The value shall be an initializer, an integer, or a
+    descriptive text.
+
+appl-config-option-description
+    For *feature* and *feature-enable* type options, the value shall be a
+    description of the configuration in case this boolean feature define is
+    defined.  Use the following wording:
+
+        In case this configuration option is defined, then ...
+
+    For *initializer* and *integer* options, the value shall describe the
+    effect of the option value.  The description should focus on the average
+    use-case.  It should not cover potential problems, constraints, obscure
+    use-cases, corner cases and everything which makes matters complicated.
+    Add these things to *appl-config-option-constraint* and
+    *appl-config-option-notes*.  Use the following wording:
+
+        The value of this configuration option defines ...
+
+appl-config-option-index
+    The value shall be a list of entries for the document index.  By default,
+    the application configuration option name is added to the index.
+
+appl-config-option-name
+    The value shall be the name of the application configuration option.  Use a
+    pattern of ``CONFIGURE_[A-Z0-9_]+`` for the name.
+
+appl-config-option-notes
+    The value shall be the notes for this option.  The notes should explain
+    everything which was omitted from the description.  It should cover all the
+    details, special cases, usage notes, error conditions, configuration
+    dependencies, and references.
+
+appl-config-option-type
+    The value shall be one of the following and nothing else:
+
+    feature
+        Use this type for boolean feature opions which have a behaviour in the
+        default configuration which is not just that the feature is disabled.
+
+    feature-enable
+        Use this type for boolean feature opions which just enables a feature.
+
+    initializer
+        Use this type for options which initialize a data structure.
+
+    integer
+        Use this type for integer options.
+
+copyrights
+    See :ref:`copyrights <ReqEngItemAttrCopyrights>`.
+
+interface-type
+    The interface type value shall be *appl-config-option*.
+
+link
+    There shall be a link to the application configuration group to which this
+    option belongs.
+
+text
+    The application configuration option requirement.
+
+type
+    The type value shall be *interface*.
+
+.. _ReqEngTestProcedure:
+
+Test Procedure
+--------------
+
+Test procedures shall be executed by the Qualification Toolchain.
+
+The test procedure items shall have the following attribute
+specializations:
+
+type
+    The type value shall be *test-procedure*.
+
+text
+    The purpose of this test procedure.
+
+platform
+    There shall be links to validation platform requirements.
+
+steps
+    The test procedure steps.  Could be a list of key-value pairs.  The key
+    is the step name and the value is a description of the actions
+    performed in this step.
+
+.. _ReqEngTestSuite:
+
+Test Suite
+----------
+
+Test suites shall use the :ref:`RTEMS Test Framework <RTEMSTestFramework>`.
+
+The test suite items shall have the following attribute specializations:
+
+type
+    The type value shall be *test-suite*.
+
+text
+    The test suite description.
+
+.. _ReqEngTestCase:
+
+Test Case
+---------
+
+Test cases shall use the :ref:`RTEMS Test Framework <RTEMSTestFramework>`.
+
+The test case items shall have the following attribute specializations:
+
+type
+    The type value shall be *test-case*.
+
+link
+    The link to the requirement validated by this test case or no links if
+    this is a unit or integration test case.
+
+ref
+    If this is a unit test case, then a reference to the :term:`software
+    item` under test shall be provided.  If this is an integration test
+    case, then a reference to the integration under test shall be provided.
+    The integration is identified by its Doxygen group name.
+
+text
+    A short description of the test case.
+
+inputs
+    The inputs to execute the test case.
+
+outputs
+    The expected outputs.
+
+The test case code may be also contained in the test case specification
+item in a *code* attribute.  This is subject to discussion on the RTEMS
+mailing list.  Alternatively, the test code could be placed directly in
+source files.  A method is required to find the test case specification of
+a test case code and vice versa.
+
+.. _ReqEngResAndPerf:
+
+Resources and Performance
+-------------------------
+
+Normally, resource and performance requirements are formulated like this:
+
+* The resource U shall need less than V storage units.
+
+* The operation Y shall complete within X time units.
+
+Such statements are difficult to make for a software product like RTEMS which
+runs on many different target platforms in various configurations.  So, the
+performance requirements of RTEMS shall be stated in terms of benchmarks.  The
+benchmarks are run on the project-specific target platform and configuration.
+The results obtained by the benchmark runs are reported in a human readable
+presentation.  The application designer can then use the benchmark results to
+determine if its system performance requirements are met.  The benchmarks shall
+be executed under different environment conditions, e.g. varying cache states
+(dirty, empty, valid) and system bus load generated by other processors.  The
+application designer shall have the ability to add additional environment
+conditions, e.g. system bus load by DMA engines or different system bus
+arbitration schemes.
+
+To catch resource and performance regressions via test suite runs there shall be
+a means to specify threshold values for the measured quantities.  The threshold
+values should be provided for each validation platform.  How this can be done
+and if the threshold values are maintained by the RTEMS Project is subject to
+discussion.
diff --git a/eng/req/management.rst b/eng/req/management.rst
new file mode 100644
index 0000000..3450471
--- /dev/null
+++ b/eng/req/management.rst
@@ -0,0 +1,76 @@
+.. SPDX-License-Identifier: CC-BY-SA-4.0
+
+.. Copyright (C) 2019, 2020 embedded brains GmbH (http://www.embedded-brains.de)
+
+Requirement Management
+======================
+
+Change Control Board
+--------------------
+
+Working with requirements usually involves a Change Control Board
+(:term:`CCB`).  The CCB of the RTEMS Project is the
+`RTEMS developer mailing list <https://lists.rtems.org/mailman/listinfo/devel>`_.
+
+There are the following actors involved:
+
+* *RTEMS users*: Everyone using the RTEMS real-time operating system to design,
+  develop and build an application on top of it.
+
+* *RTEMS developers*: The persons developing and maintaining RTEMS.  They write
+  patches to add or modify code, requirements, tests and documentation.
+
+* *RTEMS maintainers*: They are listed in the
+  `MAINTAINERS <https://git.rtems.org/rtems/tree/MAINTAINERS>`_ file and have
+  write access to the project repositories.
+
+Adding and changing requirements follows the normal patch review process.  The
+normal patch review process is described in the
+`RTEMS User Manual <https://docs.rtems.org/branches/master/user/support/contrib.html#patch-review-process>`_.
+Reviews and comments may be submitted by anyone, but a maintainer review is
+required to approve *significant* changes.  In addition for significant
+changes, there should be at least one reviewer with a sufficient independence
+from the author which proposes a new requirement or a change of an existing
+requirement.  Working in another company on different projects is sufficiently
+independent.  RTEMS maintainers do not know all the details, so they trust in
+general people with experience on a certain platform.  Sometimes no review
+comments may appear in a reasonable time frame, then an implicit agreement to
+the proposed changes is assumed.  Patches can be sent at anytime, so
+controlling changes in RTEMS requires a permanent involvement on the RTEMS
+developer mailing list.
+
+For a qualification of RTEMS according to certain standards, the requirements
+may be approved by an RTEMS user.  The approval by RTEMS users is not the
+concern of the RTEMS Project, however, the RTEMS Project should enable RTEMS
+users to manage the approval of requirements easily.  This information may be
+also used by a independent authority which comes into play with an Independent
+Software Verification and Validation (:term:`ISVV`).  It could be used to
+select a subset of requirements, e.g. look only at the ones approved by a
+certain user.  RTEMS users should be able to reference the determinative
+content of requirements, test procedures, test cases and justification reports
+in their own documentation.  Changes in the determinative content should
+invalidate all references to previous versions.
+
+Add a Requirement
+-----------------
+
+.. image:: ../../images/eng/req-add.*
+    :scale: 70
+    :align: center
+
+.. _ReqEngModifyRequirement:
+
+Modify a Requirement
+--------------------
+
+.. image:: ../../images/eng/req-modify.*
+    :scale: 70
+    :align: center
+
+Mark a Requirement as Obsolete
+------------------------------
+
+Requirements shall be never removed.  They shall be marked as obsolete.  This
+ensures that requirement identifiers are not reused.  The procedure to obsolete
+a requirement is the same as the one to :ref:`modify a requirement
+<ReqEngModifyRequirement>`.
diff --git a/eng/req/req-for-req.rst b/eng/req/req-for-req.rst
new file mode 100644
index 0000000..d38e384
--- /dev/null
+++ b/eng/req/req-for-req.rst
@@ -0,0 +1,349 @@
+.. SPDX-License-Identifier: CC-BY-SA-4.0
+
+.. Copyright (C) 2019, 2020 embedded brains GmbH (http://www.embedded-brains.de)
+
+Requirements for Requirements
+=============================
+
+.. _ReqEngIdent:
+
+Identification
+--------------
+
+Each requirement shall have a unique identifier (UID).  The question is in
+which scope should it be unique?  Ideally, it should be universally unique.
+Therefore all UIDs used to link one specification item to another should use
+relative UIDs.  This ensures that the RTEMS requirements can be referenced
+easily in larger systems though a system-specific prefix.  The standard
+ECSS-E-ST-10-06C recommends in section 8.2.6 that the identifier should reflect
+the type of the requirement and the life profile situation.  Other standards
+may have other recommendations.  To avoid a bias of RTEMS in the direction of
+ECSS, this recommendation will not be followed.
+
+The *absolute UID* of a specification item (for example a requirement) is
+defined by a leading ``/`` and the path of directories from the specification
+base directory to the file of the item separated by ``/`` characters and the
+file name without the ``.yml`` extension.  For example, a specification item
+contained in the file :file:`build/cpukit/librtemscpu.yml` inside a
+:file:`spec` directory has the absolute UID of ``/build/cpukit/librtemscpu``.
+
+The *relative UID* to a specification item is defined by the path of
+directories from the file containing the source specification item to the file
+of the destination item separated by ``/`` characters and the file name of the
+destination item without the ``.yml`` extension.  For example the relative UID
+from ``/build/bsps/sparc/leon3/grp`` to ``/build/bsps/bspopts`` is
+``../../bspopts``.
+
+Basically, the valid characters of an UID are determined by the file system
+storing the item files.  By convention, UID characters shall be restricted to
+the following set defined by the regular expression ``[a-zA-Z0-9_-]+``.  Use
+``-`` as a separator inside an UID part.
+
+In documents the URL-like prefix ``spec:`` shall be used to indicated
+specification item UIDs.
+
+The UID scheme for RTEMS requirements shall be component based.  For example,
+the UID ``spec:/classic/task/create-err-invaddr`` may specify that the
+:c:func:`rtems_task_create` directive shall return a status of
+``RTEMS_INVALID_ADDRESS`` if the ``id`` parameter is ``NULL``.
+
+A initial requirement item hierarchy could be this:
+
+* build (building RTEMS BSPs and libraries)
+
+* acfg (application configuration groups)
+
+    * opt (application configuration options)
+
+* classic
+
+    * task
+
+        * create-* (requirements for :c:func:`rtems_task_create`)
+        * delete-* (requirements for :c:func:`rtems_task_delete`)
+        * exit-* (requirements for :c:func:`rtems_task_exit`)
+        * getaff-* (requirements for :c:func:`rtems_task_get_affinity`)
+        * getpri-* (requirements for :c:func:`rtems_task_get_priority`)
+        * getsched-* (requirements for :c:func:`rtems_task_get_scheduler`)
+        * ident-* (requirements for :c:func:`rtems_task_ident`)
+        * issusp-* (requirements for :c:func:`rtems_task_is_suspended`)
+        * iter-* (requirements for :c:func:`rtems_task_iterate`)
+        * mode-* (requirements for :c:func:`rtems_task_mode`)
+        * restart-* (requirements for :c:func:`rtems_task_restart`)
+        * resume* (requirements for :c:func:`rtems_task_resume`)
+        * self* (requirements for :c:func:`rtems_task_self`)
+        * setaff-* (requirements for :c:func:`rtems_task_set_affinity`)
+        * setpri-* (requirements for :c:func:`rtems_task_set_priority`)
+        * setsched* (requirements for :c:func:`rtems_task_set_scheduler`)
+        * start-* (requirements for :c:func:`rtems_task_start`)
+        * susp-* (requirements for :c:func:`rtems_task_suspend`)
+        * wkafter-* (requirements for :c:func:`rtems_task_wake_after`)
+        * wkwhen-* (requirements for :c:func:`rtems_task_wake_when`)
+
+    * sema
+
+        * ...
+
+* posix
+
+* ...
+
+A more detailed naming scheme and guidelines should be established.  We have to
+find the right balance between the length of UIDs and self-descriptive UIDs.  A
+clear scheme for all Classic API managers may help to keep the UIDs short and
+descriptive.
+
+The specification of the validation of requirements should be maintained also
+by specification items.  For each requirement directory there should be a
+validation subdirectory named *test*, e.g. :file:`spec/classic/task/test`.  A
+test specification directory may contain also validations by analysis, by
+inspection, and by design, see :ref:`ReqEngValidation`.
+
+Level of Requirements
+---------------------
+
+The level of a requirement shall be expressed with one of the verbal forms
+listed below and nothing else.  The level of requirements are derived from RFC
+2119 :cite:`RFC2119` and ECSS-E-ST-10-06C :cite:`ECSS_E_ST_10_06C`.
+
+Absolute Requirements
+~~~~~~~~~~~~~~~~~~~~~
+
+Absolute requirements shall be expressed with the verbal form *shall* and no
+other terms.
+
+Absolute Prohibitions
+~~~~~~~~~~~~~~~~~~~~~
+
+Absolute prohibitions shall be expressed with the verbal form *shall not* and
+no other terms.
+
+.. warning::
+
+    Absolute prohibitions may be difficult to validate.  They should not be
+    used.
+
+Recommendations
+~~~~~~~~~~~~~~~
+
+Recommendations shall be expressed with the verbal forms *should* and
+*should not* and no other terms with guidance from RFC 2119:
+
+    SHOULD   This word, or the adjective "RECOMMENDED", mean that there
+    may exist valid reasons in particular circumstances to ignore a
+    particular item, but the full implications must be understood and
+    carefully weighed before choosing a different course.
+
+    SHOULD NOT   This phrase, or the phrase "NOT RECOMMENDED" mean that
+    there may exist valid reasons in particular circumstances when the
+    particular behavior is acceptable or even useful, but the full
+    implications should be understood and the case carefully weighed
+    before implementing any behavior described with this label.
+
+Permissions
+~~~~~~~~~~~
+
+Permissions shall be expressed with the verbal form *may* and no other terms
+with guidance from RFC 2119:
+
+    MAY   This word, or the adjective "OPTIONAL", mean that an item is
+    truly optional.  One vendor may choose to include the item because a
+    particular marketplace requires it or because the vendor feels that
+    it enhances the product while another vendor may omit the same item.
+    An implementation which does not include a particular option MUST be
+    prepared to interoperate with another implementation which does
+    include the option, though perhaps with reduced functionality. In the
+    same vein an implementation which does include a particular option
+    MUST be prepared to interoperate with another implementation which
+    does not include the option (except, of course, for the feature the
+    option provides.)
+
+Possibilities and Capabilities
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+Possibilities and capabilities shall be expressed with the verbal form *can*
+and no other terms.
+
+.. _ReqEngSyntax:
+
+Syntax
+------
+
+Use the Easy Approach to Requirements Syntax (:term:`EARS`) to formulate
+requirements.  A recommended reading list to get familiar with this approach is
+:cite:`Mavin:2009:EARS`, :cite:`Mavin:2010:BigEars`, and
+:cite:`Mavin:2016:LLEARS`.  Please also have a look at the EARS quick reference
+sheet :cite:`Uusitalo:2012:EARS`.  The sentence types are:
+
+* Ubiquitous
+
+    The <system name> shall <system response>.
+
+* Event-driven
+
+    *When* <optional preconditions> <trigger>, the <system name> shall <system response>.
+
+* State-driven
+
+    *While* <in state>, the <system name> shall <system response>.
+
+* Unwanted behaviour
+
+    *If* <optional preconditions> <trigger>, *then* the <system name> shall <system response>.
+
+* Optional
+
+    *Where* <feature>, the <system name> shall <system response>.
+
+The optional sentence type should be only used for application configuration
+options.  The goal is to use the *enabled-by* attribute to enable or disable
+requirements based on configuration parameters that define the RTEMS artefacts
+used to build an application executable (header files, libraries, linker command
+files).  Such configuration parameters are for example the architecture, the
+platform, CPU port options, and build configuration options (e.g. uniprocessor
+vs. SMP).
+
+Wording Restrictions
+--------------------
+
+To prevent the expression of imprecise requirements, the following terms shall
+not be used in requirement formulations:
+
+* "acceptable"
+* "adequate"
+* "almost always"
+* "and/or"
+* "appropriate"
+* "approximately"
+* "as far as possible"
+* "as much as practicable"
+* "best"
+* "best possible"
+* "easy"
+* "efficient"
+* "e.g."
+* "enable"
+* "enough"
+* "etc."
+* "few"
+* "first rate"
+* "flexible"
+* "generally"
+* "goal"
+* "graceful"
+* "great"
+* "greatest"
+* "ideally"
+* "i.e."
+* "if possible"
+* "in most cases"
+* "large"
+* "many"
+* "maximize"
+* "minimize"
+* "most"
+* "multiple"
+* "necessary"
+* "numerous"
+* "optimize"
+* "ought to"
+* "probably"
+* "quick"
+* "rapid"
+* "reasonably"
+* "relevant"
+* "robust"
+* "satisfactory"
+* "several"
+* "shall be included but not limited to"
+* "simple"
+* "small"
+* "some"
+* "state-of-the-art".
+* "sufficient"
+* "suitable"
+* "support"
+* "systematically"
+* "transparent"
+* "typical"
+* "user-friendly"
+* "usually"
+* "versatile"
+* "when necessary"
+
+For guidelines to avoid these terms see Table 11-2, "Some ambiguous terms to
+avoid in requirements" in :cite:`Wiegers:2013:SR`.  There should be some means
+to enforce that these terms are not used, e.g. through a client-side pre-commit
+Git hook, a server-side pre-receive Git hook, or some scripts run by special
+build commands.
+
+Separate Requirements
+---------------------
+
+Requirements shall be stated separately.  A bad example is:
+
+spec:/classic/task/create
+    The task create directive shall evaluate the parameters, allocate a task
+    object and initialize it.
+
+To make this a better example, it should be split into separate requirements:
+
+spec:/classic/task/create
+    When the task create directive is called with valid parameters and a free
+    task object exists, the task create directive shall assign the identifier of
+    an initialized task object to the ``id`` parameter and return the
+    ``RTEMS_SUCCESSFUL`` status.
+
+spec:/classic/task/create-err-toomany
+    If no free task objects exists, the task create directive shall return the
+    ``RTEMS_TOO_MANY`` status.
+
+spec:/classic/task/create-err-invaddr
+    If the ``id`` parameter is ``NULL``, the task create directive shall return the
+    ``RTEMS_INVALID_ADDRESS`` status.
+
+spec:/classic/task/create-err-invname
+    If the ``name`` parameter is invalid, the task create directive shall
+    return the ``RTEMS_INVALID_NAME`` status.
+
+    ...
+
+Conflict Free Requirements
+--------------------------
+
+Requirements shall not be in conflict with each other inside a specification.
+A bad example is:
+
+spec:/classic/sema/mtx-obtain-wait
+    When a mutex is not available, the mutex obtain directive shall enqueue the
+    calling thread on the wait queue of the mutex.
+
+spec:/classic/sema/mtx-obtain-err-unsat
+    If a mutex is not available, the mutex obtain directive shall return the
+    RTEMS_UNSATISFIED status.
+
+To resolve this conflict, a condition may be added:
+
+spec:/classic/sema/mtx-obtain-wait
+    When a mutex is not available and the RTEMS_WAIT option is set, the mutex
+    obtain directive shall enqueue the calling thread on the wait queue of the
+    mutex.
+
+spec:/classic/sema/mtx-obtain-err-unsat
+    If a mutex is not available, when the RTEMS_WAIT option is not set, the
+    mutex obtain directive shall return the RTEMS_UNSATISFIED status.
+
+Use of Project-Specific Terms and Abbreviations
+-----------------------------------------------
+
+All project-specific terms and abbreviations used to formulate requirements
+shall be defined in the project glossary.
+
+.. _ReqEngJustReq:
+
+Justification of Requirements
+-----------------------------
+
+Each requirement shall have a rationale or justification recorded in a
+dedicated section of the requirement file.  See *rationale* attribute for
+:ref:`ReqEngSpecItems`.
diff --git a/eng/req/tooling.rst b/eng/req/tooling.rst
new file mode 100644
index 0000000..9c175fc
--- /dev/null
+++ b/eng/req/tooling.rst
@@ -0,0 +1,149 @@
+.. SPDX-License-Identifier: CC-BY-SA-4.0
+
+.. Copyright (C) 2019, 2020 embedded brains GmbH (http://www.embedded-brains.de)
+
+Tooling
+=======
+
+Tool Requirements
+-----------------
+
+To manage requirements some tool support is helpful.  Here is a list of
+requirements for the tool:
+
+* The tool shall be open source.
+
+* The tool should be actively maintained during the initial phase of the RTEMS
+  requirements specification.
+
+* The tool shall use plain text storage (no binary formats, no database).
+
+* The tool shall support version control via Git.
+
+* The tool should export the requirements in a human readable form using the
+  Sphinx documentation framework.
+
+* The tool shall support traceability of requirements to items external to the
+  tool.
+
+* The tool shall support traceability between requirements.
+
+* The tool shall support custom requirement attributes.
+
+* The tool should ensure that there are no cyclic dependencies between
+  requirements.
+
+* The tool should provide an export to :term:`ReqIF`.
+
+Tool Evaluation
+---------------
+
+During an evaluation phase the following tools were considered:
+
+* `aNimble <https://sourceforge.net/projects/nimble/>`_
+* :term:`Doorstop`
+* `OSRMT <https://github.com/osrmt/osrmt>`_
+* `Papyrus <https://www.eclipse.org/papyrus/>`_
+* `ProR <https://www.eclipse.org/rmf/pror/>`_
+* `ReqIF Studio <https://formalmind.com/tools/studio/>`_
+* `Requirement Heap <https://sourceforge.net/projects/reqheap/>`_
+* `rmToo <http://rmtoo.florath.net/>`_
+
+The tools aNimble, OSRMT and Requirement Heap were not selected since they use
+a database.  The tools Papyrus, ProR and ReqIF are Eclipse based and use
+complex XML files for data storage.  They were difficult to use and lack good
+documentation/tutorials.  The tools rmToo and Doorstop turned out to be the
+best candidates to manage requirements in the RTEMS Project.  The Doorstop tool
+was selected as the first candidate mainly due a recommendation by an RTEMS
+user.
+
+.. _ReqEngDoorstop:
+
+Best Available Tool - Doorstop
+------------------------------
+
+:term:`Doorstop` is a requirements management tool.  It has a modern,
+object-oriented and well-structured implementation in Python 3.6 under the
+LGPLv3 license.  It uses a continuous integration build with style checkers,
+static analysis, documentation checks, code coverage, unit test and integration
+tests.  In 2019, the project was actively maintained.  Pull requests for minor
+improvements and new features were reviewed and integrated within days.  Each
+requirement is contained in a single file in :term:`YAML` format.  Requirements
+are organized in documents and can be linked to each other
+:cite:`Browning:2014:RequirementsManagement`.
+
+Doorstop consists of three main parts
+
+* a stateless command line tool `doorstop`,
+
+* a file format with a pre-defined set of attributes (YAML), and
+
+* a primitive GUI tool (not intended to be used).
+
+For RTEMS, its scope will be extended to manage specifications in general.  The
+primary reason for selecting Doorstop as the requirements management tool for
+the RTEMS Project is its data format which allows a high degree of
+customization.  Doorstop uses a directed, acyclic graph (DAG) of items.  The
+items are files in YAML format.  Each item has a set of
+`standard attributes <https://doorstop.readthedocs.io/en/latest/reference/item/>`_
+(key-value pairs).
+
+The use case for the standard attributes is requirements management.  However,
+Doorstop is capable to manage custom attributes as well.  We will heavily use
+custom attributes for the specification items.  Enabling Doorstop to effectively
+use custom attributes was done specifically for the RTEMS Project in several
+patch sets.
+
+A key feature of Doorstop is the `fingerprint of items
+<https://doorstop.readthedocs.io/en/latest/reference/item/#reviewed>`_.
+For the RTEMS Project, the fingerprint hash algorithm was changed from MD5 to
+SHA256.  In 2019, it can be considered cryptographically secure.  The
+fingerprint should cover the normative values of an item, e.g. comments etc. are
+not included.  The fingerprint helps RTEMS users to track the significant
+changes in the requirements (in contrast to all the changes visible in Git).  As
+an example use case, a user may want to assign a project-specific status to
+specification items.  This can be done with a table which contains columns for 
+
+1. the UID of the item,
+
+2. the fingerprint, and
+
+3. the project-specific status.
+
+Given the source code of RTEMS (which includes the specification items) and this
+table, it can be determined which items are unchanged and which have another
+status (e.g. unknown, changed, etc.).
+
+After some initial work with Doorstop some issues surfaced
+(`#471 <https://github.com/doorstop-dev/doorstop/issues/471>`_)
+It turned out that Doorstop is not designed as a library and contains to much
+policy. This results in a lack of flexibility required for the RTEMS Project.
+
+1. Its primary use case is requirements management. So, it has some standard
+   attributes useful in this domain, like derived, header, level, normative,
+   ref, reviewed, and text. However, we want to use it more generally for
+   specification items and these attributes make not always sense.  Having them
+   in every item is just overhead and may cause confusion.
+
+2. The links cannot have custom attributes, e.g. role, enabled-by. With
+   link-specific attributes you could have multiple DAGs formed up by the same
+   set of items.
+
+3. Inside a document (directory) items are supposed to have a common type (set
+   of attributes). We would like to store at a hierarchy level also distinct
+   specializations.
+
+4. The verification of the items is quite limited.  We need verification with
+   type-based rules.
+
+5. The UIDs in combination with the document hierarchy lead to duplication,
+   e.g. a/b/c/a-b-c-d.yml. You have the path (a/b/c) also in the file name
+   (a-b-c). You cannot have relative UIDs in links (e.g. ../parent-req) . The
+   specification items may contain multiple requirements, e.g. min/max
+   attributes.  There is no way to identify them.
+
+6. The links are ordered by Doorstop alphabetically by UID. For some
+   applications, it would be better to use the order specified by the user. For
+   example, we want to use specification items for a new build system. Here it
+   is handy if you can express things like this: A is composed of B and C.
+   Build B before C.
diff --git a/eng/req/traceability.rst b/eng/req/traceability.rst
new file mode 100644
index 0000000..012c3db
--- /dev/null
+++ b/eng/req/traceability.rst
@@ -0,0 +1,76 @@
+.. SPDX-License-Identifier: CC-BY-SA-4.0
+
+.. Copyright (C) 2019, 2020 embedded brains GmbH (http://www.embedded-brains.de)
+
+.. _ReqEngTrace:
+
+Traceability of Specification Items
+===================================
+
+The standard ECSS-E-ST-10-06C demands that requirements shall be under
+configuration management, backwards-traceable and forward-traceable
+:cite:`ECSS_E_ST_10_06C`.  Requirements are a specialization of specification
+items in RTEMS.
+
+.. _ReqEngTraceHistory:
+
+History of Specification Items
+------------------------------
+
+The RTEMS specification items should placed in the RTEMS sources using Git for
+version control.  The history of specification items can be traced with Git.
+Special commit procedures for changes in specification item files should be
+established.  For example, it should be allowed to change only one
+specification item per commit.  A dedicated Git commit message format may be
+used as well, e.g. use of ``Approved-by:`` or ``Reviewed-by:`` lines which
+indicate an agreed statement (similar to the
+`Linux kernel patch submission guidelines <https://www.kernel.org/doc/html/latest//process/submitting-patches.html#using-reported-by-tested-by-reviewed-by-suggested-by-and-fixes>`_).
+Git commit procedures may be ensured through a server-side pre-receive hook.
+The history of requirements may be also added to the specification items
+directly in a *revision* attribute.  This would make it possible to generate
+the history information for documents without having the Git repository
+available, e.g. from an RTEMS source release archive.
+
+.. _ReqEngTraceBackward:
+
+Backward Traceability of Specification Items
+--------------------------------------------
+
+Providing backward traceability of specification items means that we must be
+able to find the corresponding higher level specification item for each refined
+specification item.  A custom tool needs to verify this.
+
+.. _ReqEngTraceForward:
+
+Forward Traceability of Specification Items
+-------------------------------------------
+
+Providing forward traceability of specification items means that we must be
+able to find all the refined specification items for each higher level
+specification item.  A custom tool needs to verify this.  The links from
+parent to child specification items are implicitly defined by links from a
+child item to a parent item.
+
+.. _ReqEngTraceReqArchDesign:
+
+Traceability between Software Requirements, Architecture and Design
+-------------------------------------------------------------------
+
+The software requirements are implemented in custom YAML files, see
+:ref:`ReqEngSpecItems`.  The software architecture and design is written in
+Doxygen markup.  Doxygen markup is used throughout all header and source files.
+A Doxygen filter program may be provided to place Doxygen markup in assembler
+files.  The software architecture is documented via Doxygen groups.  Each
+Doxygen group name should have a project-specific name and the name should be
+unique within the project, e.g.  RTEMSTopLevel\ MidLevel\ LowLevel.  The link
+from a Doxygen group to its parent group is realized through the ``@ingroup``
+special command.  The link from a Doxygen group or :term:`software component`
+to the corresponding requirement is realized through a ``@satisfy{req}``
+`custom command <http://www.doxygen.nl/manual/custcmd.html>`_ which needs the
+identifier of the requirement as its one and only parameter.  Only links to
+parents are explicitly given in the Doxygen markup.  The links from a parent to
+its children are only implicitly specified via the link from a child to its
+parent.  So, a tool must process all files to get the complete hierarchy of
+software requirements, architecture and design. Links from a software component
+to another software component are realized through automatic Doxygen references
+or the ``@ref`` and ``@see`` special commands.
diff --git a/eng/req/validation.rst b/eng/req/validation.rst
new file mode 100644
index 0000000..b4d4286
--- /dev/null
+++ b/eng/req/validation.rst
@@ -0,0 +1,46 @@
+.. SPDX-License-Identifier: CC-BY-SA-4.0
+
+.. Copyright (C) 2019, 2020 embedded brains GmbH (http://www.embedded-brains.de)
+
+.. _ReqEngValidation:
+
+Requirement Validation
+======================
+
+The validation of each requirement shall be accomplished by one or more of
+the following methods and nothing else:
+
+* *By test*: A :ref:`ReqEngTestCase` specification item is provided to
+  demonstrate that the requirement is satisfied when the software product is
+  executed on the target platform.
+
+* *By analysis*: A statement is provided how the requirement is met, by
+  analysing static properties of the software product.
+
+* *By inspection*: A statement is provided how the requirement is met, by
+  inspection of the :term:`source code`.
+
+* *By review of design*: A rationale is provided to demonstrate how the
+  qualification requirement is satisfied implicitly by the software design.
+
+Validation by test is strongly recommended.  The choice of any other validation
+method shall be strongly justified.  The requirements author is obligated to
+provide the means to validate the requirement with detailed instructions.
+
+For a specification item in a parent directory it could be checked that at
+least one item in a subdirectory has a link to it.  For example a subdirectory
+could contain validation items.  With this feature you could check that all
+requirements are covered by at least one validation item.
+
+The requirement validation by analysis, by inspection, and by design
+specification items shall have the following attribute specializations:
+
+type
+    The type attribute value shall be *validation-by-analysis*,
+    *validation-by-inspection*, or *validation-by-review-of-design*.
+
+link
+    There shall be exactly one link to the validated requirement.
+
+text
+    The statement or rational of the requirement validation.