|
The SEDRIS Data Representation Model
APPENDIX A - Classes Aggregate Feature |
|---|
An instance of a concrete class derived from this DRM class specifies a collection of <Primitive Feature> and / or <Feature Hierarchy> instances, organized according to some organizing principle specific to the particular subclass of <Aggregate Feature> being considered.
For most subclasses of <Aggregate Feature>, each individual branch of the aggregation is explicitly identified by a distinct link object. The various subclasses provide different mechanisms for organizing <Feature Representation> instances, which include:
Each branch is a <Feature Hierarchy> with a different <Hierarchy Data> instance, representing a different way of organizing the same underlying collection of <Feature Representation> instances.
Each branch is a <Feature Hierarchy> with a different <Classification Data> instance, representing a different thematic layer, or a different classification of <Feature Representation> instances (e.g., roads, railroads) within a single thematic layer.
Each branch is a <Feature Hierarchy> with a distinct (but possibly overlapping), <Base LOD Data> instance, representing an alternative that is to be used at a specified level of detail.
The <Aggregate Feature> represents an octant, where each branch is a <Feature Hierarchy> representing an octant, as identified by its <Octant Data> instance.
Each branch is a <Feature Hierarchy> that is located within a different cell of an irregular spatial index, as defined by its <Perimeter Data> instance.
The <Aggregate Feature> represents a quadrant, in which each branch is a <Feature Hierarchy> representing a quadrant, as identified by its <Quadrant Data> instance.
The <Aggregate Feature> represents a regularly spaced spatial index grid, in which each branch is a <Feature Hierarchy> instance representing a different cell within the spatial index.
The <Aggregate Feature> represents something that can take on different state values for a specified EDCS Attribute Code (the state_tag, which shall have the "state-related" property). Each branch is a <Feature Hierarchy> instance with a different <State Data> instance, representing an alternative that shall used to represent the <Aggregate Feature> when it takes on the specified state value.
The <Aggregate Feature> represents something that has different representations for different time periods, so that each branch is a <Feature Hierarchy> instance with a distinct (though possibly overlapping) <Time Constraints Data> instance, representing an alternative that shall be used for the time period specified by its <Time Constraints Data>.
Each branch is a <Feature Representation>, which may be either a <Primitive Feature> or a <Feature Hierarchy> instance. The reason for organizing them into separate components is only minimally specified.
See specific subclasses for examples.
This class, through its subclasses, allows instances of <Feature Representation> to be hierarchically organized in a variety of different ways. The <Classification Related Features> subclass allows features to be organized according to their classification codes. The <Spatial Index Related Features>, <Perimeter Related Features>, <Quadrant Related Features>, and <Octant Related Features> subclasses allow features to be organized according to their locations. The <Alternate Hierarchy Related Features>, <LOD Related Features>, <State Related Features>, and <Time Related Features> subclasses allow multiple alternative representations of collections of <Feature Representation> instances to be created, with different alternatives used under different conditions. Finally, the <Union Of Features> subclass allows features to be grouped arbitrarily.
| SE_Boolean | unique_descendants; | (notes) |
|---|---|---|
| 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.
|