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The SEDRIS Data Representation Model
APPENDIX A - Classes Model Instance Template Index |
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An instance of this DRM class is used by a <Feature Model Instance> instance (FMI) or <Geometry Model Instance> instance (GMI) to specify, for a given <Expression> component of the FMI / GMI, which <Variable> instance within <Interface Template> component of the instantiated <Model> instance is receiving that <Expression> instance as its value for that FMI / GMI.
The mechanism works as follows.
Consider a <Model> instance M that contains <Variable> instances. In order to be semantically valid, M shall have an <Interface Template> component I that, by definition, has an ordered set of association relationships to each <Variable> instance within M.
The <Interface Template> instance I exists to provide access to all <Variable> instances within M, so that all FMI and GMI instances referring to M have a means of specifying values to be plugged into those <Variable> instances for a particular FMI or GMI instance referring to M.
Specifically, a model instance object referring to M (whether a <Feature Model Instance> instance or a <Geometry Model Instance> instance) provides a set of <Expression> instances to be plugged into the <Variable> instances of M. For a <Model> instance M with N <Variable> instances, the <Interface Template> component of M has 1..N ordered associations, one to each <Variable> instance within M. Each model instance of M supplies N <Expression> components, together with a <Model Instance Template Index> link object for each <Expression> component. The index field value within the <Model Instance Template Index> link object for a given <Expression> component specifies which of the N <Variable> instances of M is to be supplied with that <Expression> component as its value.
See the <Interface Template> class for examples.
The index is a one-based index, which (as described in the definition of the <Model Instance Template Index> class) serves as an index into the ordered list of <Expression> instances provided by the <Interface Template> component of the given <Model> instance.
Consequently, if the <Model> instance contains N <Variable> instances, the <Interface Template> component has N ordered associates, so the value of the index field of a <Model Instance Template Index> link object for a given <Expression> component being supplied by a model instance shall be in [1..N].
See also the constraints for this class, and for the <Feature Model Instance> class and the <Geometry Model Instance> class.
No Notes supplied.
4 A given model instance is not permitted to supply conflicting <Expression> components for a given <Variable> instance. Therefore, for any model instance instance, all its <Model Instance Template Index> link objects shall be unique.
Given the <Model> instance M that is being instantiated, the index field specifies an index into the ordered <Variable> instances associated with the <Interface Template> component of M.
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