The SEDRIS Data Representation Model
APPENDIX A - Classes
Union Of Features

Class Name: Union Of Features

Superclass - <Aggregate Feature>

Subclasses

This DRM class is concrete and has no subclasses.

Definition

An instance of this DRM class is an <Aggregate Feature> containing an arbitrary collection of <Features>.

Primary Page in DRM Diagram:

Secondary Pages in DRM Diagram:

This class appears on only one page of the DRM class diagram.

Example

  1. An airport could be represented as a <Union Of Features> that includes <Linear Feature> instances for the runways; a <Point Feature> for the control tower; and <Areal Feature> instances for the terminal and parking lots.

  2. A collection of <Areal Feature> instances that represent all forested areas within the spatial extent of the given <Environment Root>.

FAQs

What is the purpose of this class?

A <Union Of Features> provides a general-purpose mechanism for grouping together a collection of <Features>, which may include <Primitive Features>, <Feature Model Instances>, and other <Aggregate Features>. Note that a <Union Of Features> is the only type of <Aggregate Feature> that can include <Primitive Features> as direct components. They therefore tend to be used at the lowest levels of a <Feature Hierarchy>.

Constraints

Associated by (one-way)(inherited)

Associated with (two-way)(inherited)

Composed of (two-way)(inherited)

Composed of (two-way)

Composed of (two-way metadata)(inherited)

Component of (two-way)(inherited)

Inherited Field Elements

SE_Boolean unique_descendants; (notes)
SE_Boolean strict_organizing_principle; (notes)

Field Elements

SE_Feature_Union_Reason union_reason;
SE_Ordering_Reason ordering_reason; (notes)

Notes

Associated with Notes


Feature

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

Geometry_Hierarchy

 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.

Property_Grid

 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.

Composed of Notes


Image_Mapping_Function

 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.

Presentation_Domain

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

Fields Notes


unique_descendants

 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.

strict_organizing_principle

 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.

ordering_reason

 This value specifies whether the ordering of the component <Feature>
 instances of the given <Union Of Features> is semantically significant,
 and if so, what that significance is.
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Last updated: May 15, 2003 Copyright © 2003 SEDRIS™