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The SEDRIS Data Representation Model
APPENDIX B - Constraints Union Organizing Principle |
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For a <Union Of Primitive Geometry> instance U, the strict_organizing_principle and unique_descendants field values shall be SE_TRUE, and all U's <Primitive Geometry> components shall be distinct.
For a <Union Of Feature Topology> instance U, all U's <Feature Topology> components shall be distinct.
For a <Union Of Geometry Topology> instance U, all U's <Geometry Topology> components shall be distinct.
For a <Union Of Geometry Hierarchy> instance U, all U's <Geometry Hierarchy> components shall be distinct. Furthermore, no two <Geometry Hierarchy> components of U shall organize exactly the same collection of geometric data.
All members of a union shall be distinct to avoid semantic ambiguity.
In the case of two <Union Of Geometry Hierarchy> components attempting to provide alternate representations of the same underlying data, the appropriate representation mechanism is <Alternate Hierarchy Related Geometry>.
Consider a <Union Of Geometry Hierarchy> instance for which the ordering_reason is semantically significant. The same <Geometry Hierarchy> instance cannot appear twice in the union, because the semantic meaning of that instance would be ambiguous.
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