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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 is an aggregation of <Feature Hierarchy> instances, organized according to their EDCS Classification Codes (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> 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> instances indicates that they are alternate representations of the same environmental object.
An association between a <Geometry Hierarchy> instance and a <Feature> instance indicates that the <Geometry Hierarchy> and the <Feature> are alternate representations of the same environmental object.
An association between a <Property Grid> instance and a <Feature> instance indicates that the <Feature> and the <Property Grid> (or some specific cell data within that <Property Grid>) are alternate representations of the same environmental object. Each associated <Property Grid> will indicate which is the case.
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.
This is needed for cases in which an <Aggregate Feature> is significant only for a particular domain, such as radar.
If this value is SE_TRUE, each 'descendant' of this aggregation - that is, each <Feature> 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> instance appears in more than one 'branch' of the aggregation.
If this value 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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