|
The SEDRIS Data Representation Model
APPENDIX A - Classes Model Instance Template Index |
|---|
An instance of this DRM class is used by a <Feature Model Instance> (FMI) or <Geometry Model Instance> (GMI) to specify, for a given <Expression> component of the FMI / GMI, which <Variable> instance within the instanced <Model>'s <Interface Template> component is receiving that <Expression> instance as its value for that FMI / GMI.
The mechanism works as follows.
Consider a <Model> instance M which contains <Variable> instances. In order to be semantically valid, M is required to have an <Interface Template> component I, which 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 FMIs and GMIs referring to M have a means of specifying values to be plugged into those <Variable> instances for a particular FMI or GMI referring to M.
Specifically, a model instance object referring to M (whether a <Feature Model Instance> or a <Geometry Model Instance>) provides a set of <Expression> instances to be 'plugged in' to M's <Variable> instances. For a <Model> M with N <Variable> instances, M's <Interface Template> component will have 1..N ordered associations, one to each <Variable> instance within M. Each model instance of M will supply N <Expression> instances, together with a <Model Instance Template Index> instance for each <Expression> instance. The index within the <Model Instance Template Index> instance for a given <Expression> component specifies which of the N <Variable> instances of M is to be supplied with that <Expression> instance as its value.
See <Interface Template> for examples.
The index is a 1-based index, which (as described in the definition of <Model Instance Template Index>) serves as an index into the ordered list of <Expressions> provided by the given <Model>'s <Interface Template>.
Consequently, if the <Model> contains N <Variables>, the <Interface Template> will have N ordered associates, so the value of a <Model Instance Template Index> instance for a given <Expression> being supplied by a model instance shall be between 1 and N inclusive.
See also the constraints for this class, and for <Feature Model Instance>, <Geometry Model Instance>.
| SE_Integer_Positive | index; | (notes) |
|---|
No Notes supplied.
2 Naturally, a given model instance is not permitted to supply conflicting <Expression> instances for a given <Variable>, so for any model instance instance, all its <Model Instance Template Index> instances shall be unique.
Given the <Model> that is being instanced, the index field specifies an index into the ordered <Variable> list of that <Model>'s <Interface Template>.
|