SDMetrics User Manual - Projection for Rules

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Contents > 8 Defining Custom Design Metrics and Rules > 8.3 Definition of Design Rules > 8.3.3 Projection for Rules

8.3.3 Projection for Rules

The projection procedure for rules calculates a set projection for a model element (see Section 8.2.1 "Projection"), and reports any elements contained in there as violation of the rule. Consider this example:

<rule name="MissingGuard" domain="state" category="Correctness" 
      severity="1-high">
  <description>If there are two or more transitions from a choice 
      state, they all must have guards.</description>
  <projection precondition="kind='choice' and Outgoing>1"
      relation="transsource" target="transition" condition="Guards=0"
</rule>

Attributes relation, target, and condition define the projection, and are processed exactly the same way as we know them from set projections. In the above example, the projection yields, for a state, the set of outgoing transitions that have no guard.

In the context of a rule, a projection can have three additional attributes:

precondition: A condition expression that is evaluated for the model element about to be checked. If the condition is false, the rule will not be checked. In the example above, the rule is only applicable if the state is a choice state (kind='choice') and has at least two outgoing transitions (Outgoing>1).
value: defines the value of the rule that is displayed to the user. This is a metric expression, and is evaluated for the model elements returned by the projection. If the projection returns a valueset, no value needs to be specified - the value of the rule is the value returned by the projection.
mincnt: defines the minimum number of times an element must be included in the resulting multiset to be reported. You can use this feature to find and report duplicates, as shown in the next example. The default value is 1 (report all elements).

<rule name="DupName" domain="state" category="Correctness" severity="1-high">
  <description>The compound state has two or more states of 
                 the same name.</description>
  <projection relation="context" target="state" condition="name!=''"
              valueset="name" mincnt="2" />
</rule>

For rule "DupName", the projection defines the value set of names of the states of a compound state (omitting anonymous states). By setting mincnt="2", only names that occur two times or more will be reported.

Note the following restrictions that apply in the context of a rule projection:

The resulting set is always a multiset.
Attribute "recurse" is not allowed for rules. If you need the rule to operate on a recursively defined set, define the set using a regular set projection (Section 8.2.1 "Projection"), and feed that set into the rule projection with the "relset" attribute.

Section 8.3.2 "Cycle"

Contents

Section 8.3.4 "Valueset for Rules"