The SEDRIS Data Representation Model
APPENDIX A - Classes
Colour Table Group

Class Name: Colour 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 <Colour Table> instances. The primary <Colour Table> instance in the group is indicated by the primary_table_index. When a reference is made to a <Colour Table> instance (for example, from a <Colour Index> component of a <Polygon> instance), the reference identifies the <Colour Table Group> instance and the index within the <Colour Table> instance, but not the specific <Colour Table> instance within the <Colour Table Group> instance. By definition, a <Colour Index> instance refers to a <Primitive Colour> instance from the primary <Colour Table> instance of the indicated <Colour Table Group> instance. An alternate <Colour Table> instance from within the <Colour Table Group> instance can be chosen at the discretion of the data consumer.

Primary Page in DRM Diagram:

Secondary Pages in DRM Diagram:

Example

  1. Consider a <Colour Table Group> instance G with two <Colour Table> components, where the first <Colour Table> component A is for OTW viewing, and the second <Colour Table> component B is for a view as seen through night vision goggles. A <Colour Index> instance associated to G shall reference A if index = 1 but shall reference B if index = 2.

  2. A data provider is required to provide three alternate colour tables for a particular set of environmental data. A <Colour Table Group> instance with three <Colour Table> components with the same usage of OTW is provided. One <Colour Table> component defines the colours as originally created by the data modellers. The second <Colour Table> component has different shades of blue for the lakes and skies that are preferred by one set of customers. The third <Colour Table> instance contains yet another set of blues for the lakes, and different shades of green for the trees preferred by a different set of customers. The data provider identifies the first <Colour Table> component as the primary <Colour Table> component for the group.

  3. Consider a <Colour Table Group> instance with three <Colour Table> components: one for an OTW view, one for a radar view, and one for an infrared view. Each of the three <Colour Table> components contains 234 <Primitive Colour> components. Entry 234 in each <Colour Table> component in this example is a <Primitive Colour> component for the representation of granite, where that in the first <Colour Table> component represents granite in the OTW domain, that in the second <Colour Table> component represents granite in the radar domain, and that in the third <Colour Table> component represents granite in the infrared domain.

FAQs

Can a transmittal in any way refer to a <Colour Table> instance component of a <Colour Table Group> instance other than the primary <Colour Table> component?

No. The only <Colour Table> component that can be referenced of any <Colour Table Group> instance is the primary <Colour Table> instance.

Since they cannot be referenced, why bother to have alternate <Colour Table> instances within a <Colour Table Group> instance?

Because in real life, many run-time systems do have multiple colour 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; 1
SE_Integer_Positive table_size; 2

Notes

Fields Notes

primary_table_index

The primary_table_index field specifies the primary <Colour Table> component of the <Colour Table Group> instance from its ordered <Colour Table> components.

table_size

The table_size field specifies the size of all <Colour Table> components of the <Colour Table Group> instance.


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Last updated: July 26, 2006 Copyright © 2006 SEDRIS