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The SEDRIS Data Representation Model
APPENDIX A - Classes Classification Related Features |
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An instance of this DRM class specifies an aggregation of <Feature Hierarchy> instances, organized according to their ECCs, such that each component <Feature Hierarchy> instance represents
Several thematic layers of features might be grouped using a <Classification Related Features> instance, with each of its components representing a separate thematic layer (such as culture or vegetation). In such a case, the unique_descendants and strict_organizing_principle flags of the <Classification Related Features> instance should be set to SE_TRUE. The <Classification Data> link object associated with each of its components identifies the contents of each thematic layer, and each of the components is an independent topological complex and has a <Feature Topology Hierarchy>.
A region consisting of forest and water is represented as a <Classification Related Features> with strict_organizing_principle set to SE_TRUE, containing two <Union Of Features> components. The first, containing the forest features, has a <Classification Data> link object with tag = ECC_FOREST, while the second, containing the water features, has a <Classification Data> link object with tag = ECC_WATER.
Considering the first example, suppose that roads run through the forest. The forest <Union Of Features> can then be replaced with another <Classification Related Features> having 2 branches, one classified as ECC_ROAD and the other as ECC_FOREST, and the strict_organizing_principle flag in example 1's <Classification Related Features> would set to SE_FALSE, because the forest branch at the coarse level contains non-forest (in this case, road) features.
A large collection of features might be organized using a <Classification Related Features> instance, with multiple component <Union Of Features> instances, containing cultural, vegetation, and surface drainage features, respectively.
<Classification Related Features> exists to provide a mechanism for hierarchically organizing <Feature Representation> instances according to their (possibly elaborated) classification.
| 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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