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eng: Update EARS syntax
The document used the EARS syntax from 2009 which slightly changed in 2016, see "Listens Learned (8 Lessons Learned Applying EARS)". The optional pre-conditions moved to the state-driven pattern. This refined syntax fits better to the action requirements. Update #3715.
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Sebastian Huber
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66591316dc
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239644be82
@ -283,30 +283,41 @@ an :ref:`SpecTypeInterfaceForwardDeclarationItemType` item.
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Action Requirements
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-------------------
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Use :ref:`SpecTypeActionRequirementItemType` items to specify and validate
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directive calls. Action requirements are a generator for event-driven
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requirements which should be written in the following :ref:`syntax
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:ref:`SpecTypeActionRequirementItemType` items may be used to specify and
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validate directive calls. They are a generator for event-driven requirements.
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Event-driven requirements should be written in the following :ref:`syntax
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<ReqEngSyntax>`:
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*When* <optional preconditions> <trigger>, the <system name> shall
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<system response>.
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**While** <pre-condition 0>, **while** <pre-condition 1>, ..., **while**
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<pre-condition *n*>, **when** <trigger>, the <system name> shall <system
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response>.
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The <optional preconditions> are the pre-conditions of the action requirement.
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The <trigger> is the action of the action requirement. The post-conditions
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should provide a list of the <system name> shall <system response> clauses.
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Each transition in the transition map is an event-driven requirement composed
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of the pre-condition states, the action, and the post-condition states defined
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by the map entry.
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The list of *while* <pre-condition *i*> clauses for *i* from 1 to *n* in the
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EARS notation is generated by *n* pre-condition states in the action
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requirement item, see the ``pre-condition`` attribute in the
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:ref:`SpecTypeActionRequirementItemType`.
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Use ``CamelCase`` for the pre-condition names, post-condition
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names, and state names. The more conditions a directive has, the shorter
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should be the names. The transition map may be documented as a table and more
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conditions need more table columns. Use item attribute references in the
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``text`` attributes. This allows context-sensitive substitutions.
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The <trigger> in the EARS notation is defined for an action requirement item by
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the link to an :ref:`SpecTypeInterfaceFunctionItemType` or an
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:ref:`SpecTypeInterfaceMacroItemType` item using the
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:ref:`SpecTypeInterfaceFunctionLinkRole`. The code provided by the
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``test-action`` attribute defines the action code which should invoke the
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trigger directive in a particular set of pre-condition states.
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Link the action requirement item to an :ref:`SpecTypeInterfaceFunctionItemType`
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or an :ref:`SpecTypeInterfaceMacroItemType` item using the
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:ref:`SpecTypeInterfaceFunctionLinkRole`.
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Each post-condition state of the action requirement item generates a <system
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name> shall <system response> clause in the EARS notation, see the
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``post-condition`` attribute in the :ref:`SpecTypeActionRequirementItemType`.
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Each entry in the transition map is an event-driven requirement composed of the
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pre-condition states, the trigger defined by the link to a directive, and the
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post-condition states. The transition map is defined by a list of
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:ref:`SpecTypeActionRequirementTransition` descriptors.
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Use ``CamelCase`` for the pre-condition names, post-condition names, and state
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names in action requirement items. The more conditions a directive has, the
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shorter should be the names. The transition map may be documented as a table
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and more conditions need more table columns. Use item attribute references in
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the ``text`` attributes. This allows context-sensitive substitutions.
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Pre-Conditions
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^^^^^^^^^^^^^^
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@ -322,20 +333,20 @@ syntax for directive object identifier parameters:
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test-code: |
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ctx->id = 0xffffffff;
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text: |
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The ${../if/directive:/params[0]/name} parameter shall not be
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While the ${../if/directive:/params[0]/name} parameter is not
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associated with a thing.
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- name: ClassA
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test-code: |
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ctx->id = ctx->class_a_id;
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text: |
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The ${../if/directive:/params[0]/name} parameter shall be associated with a
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class A thing.
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While the ${../if/directive:/params[0]/name} parameter is associated
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with a class A thing.
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- name: ClassB
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test-code: |
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ctx->id = ctx->class_b_id;
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text: |
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The ${../if/directive:/params[0]/name} parameter shall be associated with a
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class B thing.
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While the ${../if/directive:/params[0]/name} parameter is associated
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with a class B thing.
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test-epilogue: null
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test-prologue: null
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@ -354,13 +365,13 @@ the following syntax for directive pointer parameters:
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test-code: |
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ctx->id = &ctx->id_value;
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text: |
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The ${../if/directive:/params[3]/name} parameter shall reference an
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While the ${../if/directive:/params[3]/name} parameter references an
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object of type ${../../type/if/id:/name}.
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- name: 'Null'
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test-code: |
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ctx->id = NULL;
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text: |
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The ${../if/directive:/params[3]/name} parameter shall be
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While the ${../if/directive:/params[3]/name} parameter is
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${/c/if/null:/name}.
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test-epilogue: null
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test-prologue: null
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@ -375,12 +386,12 @@ Use the following syntax for other directive parameters:
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test-code: |
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ctx->name = NAME;
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text: |
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The ${../if/directive:/params[0]/name} parameter shall be valid.
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While the ${../if/directive:/params[0]/name} parameter is valid.
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- name: Invalid
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test-code: |
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ctx->name = 0;
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text: |
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The ${../if/directive:/params[0]/name} parameter shall be invalid.
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While the ${../if/directive:/params[0]/name} parameter is invalid.
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test-epilogue: null
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test-prologue: null
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@ -171,9 +171,9 @@ Syntax
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Use the Easy Approach to Requirements Syntax (:term:`EARS`) to formulate
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requirements. A recommended reading list to get familiar with this approach is
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:cite:`Mavin:2009:EARS`, :cite:`Mavin:2010:BigEars`, and
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:cite:`Mavin:2016:LLEARS`. Please also have a look at the EARS quick reference
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sheet :cite:`Uusitalo:2012:EARS`. The sentence types are:
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:cite:`Mavin:2009:EARS`, :cite:`Mavin:2010:BigEars`,
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:cite:`Mavin:2016:LLEARS`, and `Alisair Mavin's web site
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<https://alistairmavin.com/ears/>`_. The patterns are:
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* Ubiquitous
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@ -181,22 +181,34 @@ sheet :cite:`Uusitalo:2012:EARS`. The sentence types are:
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* Event-driven
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*When* <optional preconditions> <trigger>, the <system name> shall <system response>.
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**When** <trigger>, the <system name> shall <system response>.
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* State-driven
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*While* <in state>, the <system name> shall <system response>.
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**While** <pre-condition>, the <system name> shall <system response>.
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* Unwanted behaviour
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*If* <optional preconditions> <trigger>, *then* the <system name> shall <system response>.
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**If** <trigger>, **then** the <system name> shall <system response>.
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* Optional
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*Where* <feature>, the <system name> shall <system response>.
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**Where** <feature is included>, the <system name> shall <system response>.
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The optional sentence type should be only used for application configuration
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options. The goal is to use the *enabled-by* attribute to enable or disable
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* Complex
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**Where** <feature 0 is included>, **where** <feature 1 is included>, ...,
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**where** <feature *n* is included>, **while** <pre-condition 0>, **while**
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<pre-condition 1>, ..., **while** <pre-condition *m*>, **when** <trigger>,
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the <system name> shall <system response>.
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**Where** <feature 0 is included>, **where** <feature 1 is included>, ...,
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**where** <feature *n* is included>, **while** <pre-condition 0>, **while**
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<pre-condition 1>, ..., **while** <pre-condition *m*>, **if** <trigger>,
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**then** the <system name> shall <system response>.
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The optional pattern should be only used for application configuration
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options. The goal is to use the ``enabled-by`` attribute to enable or disable
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requirements based on configuration parameters that define the RTEMS artefacts
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used to build an application executable (header files, libraries, linker command
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files). Such configuration parameters are for example the architecture, the
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@ -345,7 +357,7 @@ Justification of Requirements
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-----------------------------
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Each requirement shall have a rationale or justification recorded in a
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dedicated section of the requirement file. See *rationale* attribute for
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dedicated section of the requirement file. See ``rationale`` attribute for
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:ref:`ReqEngSpecificationItems`.
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.. _ReqEngValidation:
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