The SEDRIS Data Representation Model
APPENDIX A - Classes
Feature Volume

Class Name: Feature Volume

Superclass - <Feature Topology>

Subclasses

This DRM class is concrete and has no subclasses.

Definition

An instance of this DRM class is a three-dimensional <Feature Topology> instance used to represent the region of space that corresponds to parts of zero or more <Volumetric Feature> instances, bounded by two or more <Feature Face> instances.

Primary Page in DRM Diagram:

Secondary Pages in DRM Diagram:

Example

  1. Consider a <Volumetric Feature> instance representing a building as depicted in Figure 6.17:

    Feature Volume, Example 1

    Figure 17 — <DRM Feature Volume> example

    It has:

    1. an associated <Feature Volume> instance that defines its extent, shape, and topological relationships;
    2. a <Classification Data> component that classifies it as an ECC_BUILDING;
    3. <Property Value> components that describe its characteristics, such as material composition; and
    4. a <Label> component that identifies it as "The Empire State Building".

FAQs

When are <Feature Volume> instances required?

<Feature Volume> instances are required whenever there are <Volumetric Feature> instances, regardless of the feature topology level.

Are there any geometric constraints on <Feature Volume> instances?

Yes. <Feature Volume> instances must always have closed external boundaries, and their interiors must be fully connected. At feature topology level 5, the interiors of <Feature Volume> instances may not intersect or overlap one another, and <Feature Volume> instances may meet only along one or more common <Feature Face> instances.

Can <Feature Volume> instances exist at any feature topology level?

Yes. <Feature Volume> instances may exist at any feature topology level in order to define the extents of <Volumetric Feature> instances. At feature topology level 5, the collection of <Feature Volume> instances must exhaustively and exclusively partition the 3-dimensional topological space, such that exactly two <Feature Volume> instances shall be bounded by each <Feature Face> instance.

Looking at the relationships allowed for <Feature Topology> instances, we note that the <Feature Node> to <Feature Node> association, and the <Feature Edge> to <Feature Edge> association are "many to many", while the <Feature Face> to <Feature Face> association is "optional to optional". Why is there no corresponding association between <Feature Volume> instances?

These associations exist to support cross-tile topology. This refers to topological relationships that cross multiple branches below a <Spatial Index Related Features> instance, a <Spatial Index Related Feature Topology> instance, a <Perimeter Related Features> instance, or a <Perimeter Related Feature Topology> instance. <Feature Node> instances, <Feature Edge> instances, and, in 3D, <Feature Face> instances can be located on the boundary of a tile. When this happens, they have "counterparts" in each of the adjacent tiles that share the boundary. These associations allow <Feature Node> instances, <Feature Edge> instances, and <Feature Face> instances to identify their counterparts, if any.

In 2D,

In 3D,

Constraints

Associated by (one-way)

Associated with (two-way)

Composed of (two-way) (inherited)

Composed of (two-way)

Component of (two-way) (inherited)

Inherited Field Elements

This class has no inherited field elements.

Field Elements

SE_Boolean universal; 5

Notes

Associated from Notes


Feature_Face

The <Feature Face> instances that border the <Feature Volume> instance indicate the relationship by their association to the <Feature Volume> instance. The converse of this relationship is that between <Feature Volume Shell> instances and <Feature Face> instances.

Associated with Notes


Feature_Edge

If the <Feature Volume> instance has an association relationship with a <Feature Edge> instance, that <Feature Edge> instance is contained within the <Feature Volume> instance.


Feature_Node

If the <Feature Volume> instance has an association relationship with a <Feature Node> instance, that <Feature Node> instance is contained within the <Feature Volume> instance.

Composed of Notes


Feature_Volume_Shell

The first <Feature Volume Shell> instance associated with a <Feature Volume> instance is its external shell, while the remaining, if any, are its internal shells. Exception: Since the universal <Feature Volume> instance has no external boundary, all of its shells are internal shells.

Fields Notes

universal

The universal field specifies that the <Feature Volume> instance is the universal <Feature Volume> instance. Within a 3D tile that has feature topology level 5, the universal <Feature Volume> instance lies outside any other volumes. Since the external boundary of the universal <Feature Volume> instance is conceptually at infinity, a <Feature Volume> instance that has this field set to SE_TRUE has no external <Feature Volume Shell> instance.


Prev: Feature Topology Hierarchy. Next: Feature Volume Shell. Up:Index.

Last updated: July 26, 2006 Copyright © 2006 SEDRIS