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The SEDRIS Data Representation Model
APPENDIX A - Classes Property Set Table Group |
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An instance of this DRM class specifies an interchangeable group of one or more <Property Set Table> instances. The primary <Property Set Table> component of the group is indicated by the primary_table_index. When a reference is made to a <Property Set Table> instance (for example, from a <Property Set Index> component of a <Polygon> instance), the reference identifies the <Property Set Table Group> instance and the index within the <Property Set Table> instance, but not the specific <Property Set Table> component of the <Property Set Table Group> instance. By definition, a <Property Set Index> instance refers to a <Property Set> component of the primary <Property Set Table> component of the indicated <Property Set Table Group> instance. An alternate <Property Set Table> instance from within the <Property Set Table Group> instance can be chosen at the discretion of the data consumer.
Consider a transmittal containing a <Property Set Table Library> instance with only one <Property Set Table Group> component, which in turn has only one <Property Set Table> component. That <Property Set Table> instance is the one and only <Property Set Table> instance for the entire transmittal.
A <Property Set Table Group> instance contains two <Property Set Table> components: one for normal, OTW viewing and the other to change the appearance of the view to be a view as seen through night vision goggles.
A data provider is required to provide three alternate tables of properties, in this example colours and textures, for a particular set of environmental data. A <Property Set Table Group> instance with three <Property Set Table> components with the same usage of OTW is provided. One <Property Set Table> component defines the colours and textures as originally created by the data modellers. The second <Property Set Table> component has different shades of blue for the lakes and skies that are preferred by one set of customers. The third <Property Set Table> component contains yet another set of blues for the lakes, different textures for the lakes and different shades of green for the trees preferred by a different set of customers. The data provider identifies the first <Property Set Table> component as the primary <Property Set Table> component for the group.
No. The only <Property Set Table> component that can be referenced in any <Property Set Table Group> instance is the primary <Property Set Table> component.
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.
The primary_table_index specifies the primary <Property Set Table> component from the ordered <Property Set Table> components of the <Property Set Table Group> instance.
The table_size field specifies the size of each <Property Set Table> component of the <Property Set Table Group> instance.
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