The SEDRIS Data Representation Model
APPENDIX A - Classes
Alternate Hierarchy Related Geometry

Class Name: Alternate Hierarchy Related Geometry

Superclass - <Aggregate Geometry>

Subclasses

This DRM class is concrete and has no subclasses.

Definition

An instance of this DRM class specifies an aggregation of <Geometry Hierarchy> instances, in which each <Geometry Hierarchy> component is an alternate representation of the same environmental entity, and the corresponding <Hierarchy Data> link object indicates why that particular alternate representation was provided.

Primary Page in DRM Diagram:

Secondary Pages in DRM Diagram:

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

Example

  1. Consider a collection of <Geometry Representation> instances representing a specific spatial region, for which there is a requirement that the <Geometry Representation> instances shall be efficiently accessible both by location and by classification (such as ECC_ROAD, ECC_RIVER, ECC_VEGETATION).

    To satisfy this requirement, the data provider has chosen to use an <Alternate Hierarchy Related Geometry> instance with two components, in which one component (in this example, a <Spatial Index Related Geometry> component) organizes the <Geometry Representation> instances spatially, while a second component (a <Classification Related Geometry> component) organizes the <Geometry Representation> instances by ECC. The <Alternate Hierarchy Related Geometry> instance is related to its <Spatial Index Related Geometry> component through a <Hierarchy Data> link object with alternate_representation_reason containing the string "accessibility by location". The <Alternate Hierarchy Related Geometry> instance is related to its <Classification Related Geometry> component through a <Hierarchy Data> link object with alternate_representation_reason containing the string "accessibility by classification".

FAQs

What is the purpose of this class?

This class allows a single collection of <Geometry Representation> instances to be hierarchically organized in two or more different ways. In one branch, the <Geometry Representation> instances might be organized spatially, while in another, 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.

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;

9

SE_Boolean

strict_organizing_principle;

10

Notes

Associated to Notes


Feature_Representation

An association between a <Feature Representation> instance and a <Geometry Hierarchy> instance indicates that the environmental object(s) that they represent have the semantic relationship indicated by the <Base Association Data> link object on the association relationship.


Geometry_Hierarchy

An association between two <Geometry Hierarchy> instances indicates that the environmental object(s) that they represent have the semantic relationship indicated by the <Base Association Data> link object on the association relationship.

Associated from Notes


Feature_Representation

An association between a <Feature Representation> instance and a <Geometry Hierarchy> instance indicates that the environmental object(s) that they represent have the semantic relationship indicated by the <Base Association Data> link object on the association relationship.


Geometry_Hierarchy

An association between two <Geometry Hierarchy> instances indicates that the environmental object(s) that they represent have the semantic relationship indicated by the <Base Association Data> link object on the association relationship.


Hierarchy_Summary_Item

An association from a <Hierarchy Summary Item> instance to a <Geometry Hierarchy> instance indicates that the <Hierarchy Summary Item> instance summarizes that <Geometry Hierarchy> instance.


Reference_Surface

An association from a <Reference Surface> instance to a <Geometry Hierarchy> instance indicates that the <Geometry Hierarchy> instance organizes the geometric objects that specify the reference surface geometry of the <Reference Surface> instance.

Composed of Notes


Collision_Volume

In the case where multiple <Collision Volume> components are specified for the <Aggregate Geometry> instance, the union of the volumes thus specified is used in collision detection.


LSR_Transformation

An <Aggregate Geometry> instance can have an <LSR Transformation> component only when the <Aggregate Geometry> instance is within the scope of an LSR 3D SRF.

Fields Notes

unique_descendants

If the value of the unique_descendants field is SE_TRUE, each descendant of this aggregation, that is, each <Geometry Representation> instance that exists in the component tree rooted at the <Aggregate Geometry> instance 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 <Geometry 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.

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Last updated: June 24, 2007 Copyright © 2007 SEDRIS™