defScenario

 

The defScenario form is useful for setting up problems in which the behavior of a system is to be predicted from a set of initial conditions.

 
Figure: A scenario is defined with the defModelFragment form. A scenario specifies an initial value problem. This scenario definition provides a mixture of quantitative, qualitative, and structural information. The description is also incomplete (e.g. the diameter and length of the pipe are not provided). Some implementations are able to handle such incomplete specifications.

 (defScenario Scene name

		 [ :individuals
   ((individual     [ :type type ] ) ) ]

		 [ :initially initially ]

		 [ :throughout throughout ]

		 [ :boundary boundary ]

		 [ :documentation ;SPMlt;string;SPMgt; ]

		 [ :substitutions ((symbol form )  ) ])

:individuals

The :individuals clause specifies a subset of the objects that are initially known to be of interest. The domain theory may allow the existence of other individuals to be inferred. The individual is an object constant denoting an object, not a relation or function.

:initially

The :initially clause specifies conditions that initially hold in the scenario. It is a list of literals under an implicit conjunction. Initially may specify relations between quantities, time-dependent relations, and perhaps an assignment for the variable time.

:throughout

The :throughout clause specifies conditions that hold throughout the scenario. It is a list of literals under an implicit conjunction.

:boundary

The :boundary clause specifies a set of quantity conditions that define the boundary of the scenario. This is distinct from the :throughout conditions, which must be true. Violating the :boundary conditions is simply an indication that predictions are no longer interesting. Currently, the :boundary clause is not part of the formal semantics of the language.

:substitutions

The :substitutions field defines a set of purely syntactic substitutions that are applied prior to the replacements described above. Each element in the field is a list containing a symbol and an arbitrary form. The form is substituted for the symbol wherever it appears within the original definition (excluding the substitutions field). The substitutions are not inherited, and are not available outside of the definition in any way.

After the substitutions have been performed and and the translations required to make time dependence explicit (See section , page ) have been made, the semantics of the defScenario form is readily defined.