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 <Feature Representations>.

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 <Feature Representations>, 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 to (one-way) (inherited)

Associated by (one-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_Union_Reason union_reason; (notes)
SE_Ordering_Reason ordering_reason; (notes)

Notes

Associated to Notes


Feature_Representation

 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.

Geometry_Hierarchy

 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.

Property_Grid

 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.

Associated from Notes


Feature_Representation

 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.

Geometry_Hierarchy

 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.

Property_Grid

 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.

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

 A <Presentation Domain> component is needed for instances of
 <Aggregate Feature> that are significant only for a particular domain,
 such as radar.

Fields Notes


unique_descendants

 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.

strict_organizing_principle

 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.

union_reason

 The union_reason field specifies the reason why the given instance of
 <Union Of Features> was created to organize its components.

ordering_reason

 The ordering_reason field specifies whether the ordering of the
 component <Feature Representation>
 instances of the given <Union Of Features> instance is semantically
 significant, and if so, what that significance is.
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Last updated: July 16, 2004 Copyright © 2004 SEDRIS™