Definition

Note that where this constraint specifies that "instances" of an abstract class may be published, the instances of all concrete classes descended from that abstract class may be published.

1. Instances of the following classes may be published.

   • <Aggregate Feature>
   • <Aggregate Geometry>
   • <Colour Table Group>
   • <Environment Root>
   • <Feature Model>
   • <Feature Topology>
   • <Feature Topology Hierarchy>
   • <Geometry Model>
   • <Geometry Topology>
   • <Geometry Topology Hierarchy>
   • <Image>
   • <Library>
   • <Model>
   • <Property Grid Hook Point>
   • <Property Set Table Group>
   • <Property Table>
   • <Separating Plane Relations>
   • <Sound>
   • <Symbol>
2. Instances of the following classes may be published, where they serve the role of link objects.
   • <Base LOD Data>
   • <Classification Data>
   • <Hierarchy Data>
   • <Octant Data>
   • <Quadrant Data>
   • <Perimeter Data>
   • <Separating Plane Data>
   • <Spatial Index Data>
   • <State Data>
   • <Time Constraints Data>
3. An instance of a class not covered by 1 or 2 above shall not be published.

Rationale

1. <Environment Root> instances and <Library> instances are desired for ITR.

2. The DRM objects organized by <Library> instances are desired for ITR.

   1. Within a <Data Table Library> instance, only <Property Table> instances may be referenced by <Property Table Reference> instances.

      <Mesh Face Table> instances are bound to specific <Finite Element Mesh> instances, and do not appear within a <Data Table Library>.

   2. The remaining classes for which instances are referenced within <Library> instances are

      • <Colour Table Group> - referenced by <Colour Index>
      • <Feature Model> - referenced by <Feature Model Instance>
      • <Geometry Model> - referenced by <Geometry Model Instance>
      • <Image> - referenced by <Image Mapping Function>
      • <Property Set Table Group> - referenced by <Property Set Index>
      • <Sound> - referenced by <Sound Instance>
      • <Symbol> - referenced by <Label>

3. <Feature Topology> and <Geometry Topology> instances are used to build topology hierarchies, and may be referenced in multiple places under cross-tile topology. When used in ITR, their link objects must also be published to form valid relationships.

4. The various concrete subclasses under <Aggregate Feature> are desired for ITR, and are used to build feature hierarchies. When used in ITR, their link objects must also be published to form valid relationships. Similar reasoning holds for the subclasses of <Aggregate Geometry>, with the addition of <Separating Plane Relations> and <Separating Plane Data> for <Separating Plane Related Geometry>.

Example

1. Consider a <Model> instance A with a <Geometry Model> component GM_A in transmittal T_A, such that the data provider creating transmittal T_B wishes to create a <Geometry Model Instance> instance GMI_B in T_B that references GM_A.

   Since GMI_B will reside in transmittal T_B and GM_A is in T_A, an inter-transmittal reference (ITR) is needed to create the association from GMI_B to GM_A, so data provider B can create the relationship only if data provider A published GM_A. Since <Geometry Model> is on the list of classes for which instances may be published, the remainder of the issue is a matter for negotiation with data provider A to publish GM_A when creating transmittal T_A.

FAQs

Why aren't <Union Of Features> and the other subclasses of <Aggregate Feature> on the list of classes for which instances may be published?

Please re-read the constraint; instances of concrete classes descended from <Aggregate Feature> are permitted to be published.

Why isn't <Union Of Geometry Hierarchy> on the list of classes for which instances may be published?

It is on the list of classes, since it is a subclass of <Union Of Geometry>, which in turn is a subclass of <Aggregate Geometry>.