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The SEDRIS Data Representation Model
APPENDIX A - Classes Alternate Hierarchy Related Features |
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An instance of this DRM class specifies an aggregation of <Feature Hierarchy> instances, in which each component <Feature Hierarchy> is an alternate representation of the same environmental entity, and the corresponding <Hierarchy Data> instance indicates why that particular alternate representation was provided.
Consider a collection of <Feature Representation> instances representing a specific spatial region, for which there is a requirement that the <Feature Representation> instances shall be efficiently accessible both by location and by classification (such as ECC_ROAD, ECC_RIVER, ECC_VEGETATION).
To satisfy this requirement, the data provider has chosen to use an <Alternate Hierarchy Related Features> instance with two components, in which one component (in this example, a <Quadrant Related Features> instance) organizes the <Feature Representation> instances spatially, while a second component (a <Classification Related Features> instance) organizes the <Feature Representation> instances by ECC.
This class allows a single collection of <Feature Representation> instances to be hierarchically organized in two or more different ways. In one component, the <Feature Representation> instances might be organized spatially, while in another component they might be organized by classification. Each branch of an instance of this class provides a different access path to the same objects, where each branch is organized to be efficient with respect to a different access pattern.
| SE_Boolean | unique_descendants; | (notes) |
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| SE_Boolean | strict_organizing_principle; | (notes) |
An association between two <Feature Representation> instances indicates that the environmental object(s) that they represent have the semantic relationship indicated by the <Base Association Data> instance on the association relationship.
An association between a <Geometry Hierarchy> instance and a <Feature Representation> instance indicates that the environmental object(s) that they represent have the semantic relationship indicated by the <Base Association Data> instance on the association relationship.
An association between a <Property Grid> instance and a <Feature Representation> instance indicates that the environmental object(s) represented by the <Feature Representation> instance and the <Property Grid> instance (or some specific cell data within that <Property Grid> instance) have the semantic relationship indicated by the <Base Association Data> instance on the association relationship. Each associated <Property Grid> instance will indicate whether the entire <Property Grid> instance or only some specific cell data within it is participating in the relationship in question.
An association between two <Feature Representation> instances indicates that the environmental object(s) that they represent have the semantic relationship indicated by the <Base Association Data> instance on the association relationship.
An association between a <Geometry Hierarchy> instance and a <Feature Representation> instance indicates that the environmental object(s) that they represent have the semantic relationship indicated by the <Base Association Data> instance on the association relationship.
An association between a <Property Grid> instance and a <Feature Representation> instance indicates that the environmental object(s) represented by the <Feature Representation> instance and the <Property Grid> instance (or some specific cell data within that <Property Grid> instance) have the semantic relationship indicated by the <Base Association Data> instance on the association relationship. Each associated <Property Grid> instance will indicate whether the entire <Property Grid> instance or only some specific cell data within it is participating in the relationship in question.
This relationship exists to support *attributes for derived objects.* That is, these components are used only to specify texture mapping information for geometry that is to be derived from the <Aggregate Feature> by the consumer. These <Image Mapping Function> instances shall use <Image Anchor> components to specify the mapping.
A <Presentation Domain> component is needed for instances of <Aggregate Feature> that are significant only for a particular domain, such as radar.
If the value of the unique_descendants field is SE_TRUE, each descendant, that is, each <Feature Representation> instance that exists in the component tree rooted at the given <Aggregate Feature>, shall be unique, in the sense that it shall appear in only one branch of this aggregation. If unique_descendants is SE_FALSE, at least one <Feature Representation> instance appears in more than one branch of the aggregation.
If the value of the strict_organizing_principle field is SE_TRUE, each branch of this aggregation strictly complies with the organizing principle for its particular subclass. If this value is SE_FALSE, at least one branch does not strictly comply with the given organizing principle. See the organizing principle constraint for each specific subclass for details.
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