|
The SEDRIS Data Representation Model
APPENDIX A - Classes Alternate Hierarchy Related Features |
|---|
An instance of this DRM class is 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.
The collection of <Feature> instances representing a specific spatial region shall be accessed efficiently both by location (e.g., for display), and by classification (e.g., roads, then rivers, then vegetation). To accommodate this, an <Alternate Hierarchy Related Features> instance with two components can be used, in which one component consists of a <Quad Tree Related Features> instance, which organizes the <Feature> instances by location, and the other component consists of a < Classification Related Features> instance, which organizes the <Feature> instances by EDCS Classification Code (ECC).
This class allows a single collection of <Feature> instances to be hierarchically organized in two or more different ways. In one component, the <Features> might be organized spatially, while in another component they might be organized by classification. This provides two (or more) different access paths to the same objects, each organized to be efficient with respect to a different access pattern.
| SE_Boolean | unique_descendants; | (notes) |
|---|---|---|
| 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> 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 Functions> shall use <Image Anchor> components to specify the mapping.
This is needed because in many cases, an <Aggregate Feature> may be significant only for a particular domain, e.g. radar.
If this value is SE_TRUE, each 'descendant' of this aggregation - that is, each <Feature> object 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> object 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.
|