The SEDRIS Data Representation Model
APPENDIX A - Classes
Property Set Table Group

Class Name: Property Set Table Group

Superclass - <SEDRIS Abstract Base>

Subclasses

This DRM class is concrete and has no subclasses.

Definition

An instance of this DRM class specifies an interchangeable group of one or more <Property Set Table> instances. The primary <Property Set Table> in the group is indicated by the primary_table_index. When a reference is made to a <Property Set Table> (for example, from a <Property Set Index> component of a <Polygon>), the reference identifies the <Property Set Table Group> and the index within the <Property Set Table>, but not the specific <Property Set Table> within the <Property Set Table Group>. By definition, a <Property Set Index> refers to a <Property Set> from the primary <Property Set Table> of the indicated <Property Set Table Group>. An alternate <Property Set Table> from within the <Property Set Table Group> can be chosen at the discretion of the data consumer.

Primary Page in DRM Diagram:

Secondary Pages in DRM Diagram:

Example

  1. One <Property Set Table Group> in the transmittal, and that group has only one <Property Set Table> within the group. That <Property Set Table> is the one and only <Property Set Table> for the entire transmittal.

  2. A <Property Set Table Group> with two <Property Set Table> components, one for normal, Out The Window (OTW) viewing, the other to change the appearance of the view to be a view as seen through Night Vision Goggles (NVG).

  3. A <Property Set Table Group> with three <Property Set Table> components with the same usage of OTW. Why three tables? One <Property Set Table> defines the colours and textures as originally created by the data modelers. The second <Property Set Table> has different shades of blue for the lakes and skies because a company VIP came through and didn't like the blues that were there. The third <Property Set Table> contains yet another set of blues for the lakes, different textures for the lakes and different shades of green for the trees and tanks, because the customer in charge of the program came through and didn't think the colours and textures were realistic.

FAQs

Can a transmittal in any way refer to an <Property Set Table> in an <Property Set Table Group> other than the primary <Property Set Table>?

No. The only <Property Set Table> that can be referenced in any <Property Set Table Group> is the primary <Property Set Table>.

Since they cannot be referenced in a transmittal, why bother to have alternate <Property Set Table> instances within a <Property Set Table Group>?

Because in real life, many run-time systems have multiple colour and material tables they can switch between for various reasons, and these tables should be shared to promote interoperability. See the example section, below.

Constraints

Associated by (one-way)

Composed of (two-way)

Composed of (two-way metadata)

Component of (two-way)

Inherited Field Elements

This class has no inherited field elements.

Field Elements

SE_Integer_Positive primary_table_index; (notes)
SE_Integer_Positive table_size; (notes)

Notes

Fields Notes


primary_table_index

 The primary_table_index (which is 1-based) specifies the primary
 <Property Set Table> component from the ordered
 <Property Set Table> components of the given
 <Property Set Table Group> instance.

table_size

 The table_size field specifies the size of each
 <Property Set Table> within the given
 <Property Set Table Group> instance.

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Last updated: July 16, 2004 Copyright © 2004 SEDRIS