Table 6.8 — DRM_Aggregate_Feature

Property

Description

Class
  • <DRM Aggregate Feature>

Superclass

Subclass

Definition

An instance of this DRM class specifies a collection of <DRM Primitive Feature> and / or <DRM Feature Hierarchy> instances, organized according to some organizing principle specific to the particular subclass of <DRM Aggregate Feature> being considered.

For most subclasses of <DRM Aggregate Feature>, each individual branch of the aggregation is explicitly identified by a distinct link object. The various subclasses provide different mechanisms for organizing <DRM Feature> instances, which include:

ALTERNATE HIERARCHY:

Each branch is a <DRM Feature Hierarchy> with a different <DRM Hierarchy Data> instance, representing a different way of organizing the same underlying collection of <DRM Feature> instances.

CLASSIFICATION:

Each branch is a <DRM Feature Hierarchy> with a different <DRM Classification Data> instance, representing a different thematic layer, or a different classification of <DRM Feature> instances (e.g., roads, railroads) within a single thematic layer.

LEVEL_OF_DETAIL:

Each branch is a <DRM Feature Hierarchy> with a distinct (but possibly overlapping), <DRM Base Level Of Detail Data> instance, representing an alternative that is to be used at a specified level of detail.

OCTANT:

The <DRM Aggregate Feature> represents an octant, where each branch is a <DRM Feature Hierarchy> representing an octant, as identified by its <DRM Octant Data> instance.

PERIMETER:

Each branch is a <DRM Feature Hierarchy> that is located within a different cell of an irregular spatial index, as defined by its <DRM Perimeter Data> instance.

QUADRANT:

The <DRM Aggregate Feature> represents a quadrant, in which each branch is a <DRM Feature Hierarchy> representing a quadrant, as identified by its <DRM Quadrant Data> instance.

SPATIAL_INDEX:

The <DRM Aggregate Feature> represents a regularly spaced spatial index grid, in which each branch is a <DRM Feature Hierarchy> instance representing a different cell within the spatial index.

STATE:

The <DRM 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 <DRM Feature Hierarchy> instance with a different <DRM State Data> instance, representing an alternative that shall used to represent the <DRM Aggregate Feature> when it takes on the specified state value.

TIME:

The <DRM Aggregate Feature> represents something that has different representations for different time periods, so that each branch is a <DRM Feature Hierarchy> instance with a distinct (though possibly overlapping) <DRM Time Constraints Data> instance, representing an alternative that shall be used for the time period specified by its <DRM Time Constraints Data>.

UNION:

Each branch is a <DRM Feature>, which may be either a <DRM Primitive Feature> or a <DRM Feature Hierarchy> instance. The reason for organizing them into separate components is only minimally specified.

Class diagram

Figure 6.6 — DRM_Aggregate_Feature

Inherited field elements

Field name

Range

Field data type

None

    

Field elements

Field name

Range

Field data type

unique_descendants1

 

Boolean

strict_organizing_principle2

 

Boolean

Associated to (one-way) (inherited)
  • None.

Associated to (one-way)
  • None.

Associated by (one-way) (inherited)

Associated by (one-way)
  • None.

Associated with (two-way) (inherited)

Associated with (two-way)
  • None.

Composed of (two-way) (inherited)

Composed of (two-way)

Composed of (two-way metadata) (inherited)

Composed of (two-way metadata)
  • None.

Component of (two-way) (inherited)

Component of (two-way)
  • None.

Constraints

Clarifications

1 If this value is TRUE, each “descendant” of this aggregation - that is, each <DRM Feature> instance that exists in the component tree rooted at the given <DRM Aggregate Feature> - shall be unique, in the sense that it shall appear in only one “branch” of this aggregation. If unique_descendants is FALSE, at least one <DRM Feature> instance appears in more than one “branch” of the aggregation.

2 If this value is TRUE, each “branch” of this aggregation strictly complies with the organizing principle for its particular subclass. If this value is 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.

3 An association between two <DRM Feature> instances indicates that they are alternate representations of the same environmental object.

4 An association between a <DRM Geometry Hierarchy> instance and a <DRM Feature> instance indicates that the <DRM Geometry Hierarchy> and the <DRM Feature> are alternate representations of the same environmental object.

5 An association between a <DRM Property Grid> instance and a <DRM Feature> instance indicates that the <DRM Feature> and the <DRM Property Grid> (or some specific cell data within that <DRM Property Grid>) are alternate representations of the same environmental object. Each associated <DRM Property Grid> will indicate which is the case.

6 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 <DRM Aggregate Feature> by the consumer. These <DRM Image Mapping Function> instances shall use <DRM Image Anchor> components to specify the mapping.

7 This is needed for cases in which an <DRM Aggregate Feature> is significant only for a particular domain, such as radar.

Example(s)

See specific subclasses for examples.