Rule Name: Precedence of Attribute Set Index

Definition

Geometry or Feature objects may contain attribute and/or meta data objects and also Attribute Set Index objects that refer to Attribute Sets. If there is a clash between the attribute or meta data objects that are contained by the Geometry or Feature and any attribute or meta data objects that are contained by Attribute Sets, then objects contained directly by Geometry or Features take precedence.

Geometry and Features may contain an ordered list of Attribute Set Index objects. If a Geometry or Feature contains references to more than one Attribute Set and there is a clash between the attribute objects they contain then attribute objects contained in Attribute Sets referenced first in this ordered list have precedence over those contained in Attribute Sets that are referenced later.

Precedence will behave differently depending on the multiplicity of the relationship that the attribute or meta data object in question has with the containing Geometry or Feature. In the event of a clash, the following rules will apply based on this enumeration.

• Zero or one:
  The object contained directly by the Geometry or Feature is used. If the clash is between objects in Attribute Sets, then the object contained in the Attribute Set that is referenced earliest in the list of Attribute Set Index objects is used.
• Zero or more:
  Those contained directly by the Geometry or Feature are used, followed by those contained in the Attribute Sets, in the order that the Attribute Sets are referenced by the Geometry or Feature.
• Zero or more {ordered}:Those contained directly by the Geometry or Feature are used in order. Those contained in the Attribute Set referenced by the first Attribute Set Index object in the list are then used, in order. Then those contained in the Attribute Set referenced by the second Attribute Set Index object in the list, in order.

Rationale

Objects contained directly by Geometry or Features are more closely related to the Geometry or Feature than those contained in an Attribute Set; they will be specific while those in an Attribute Set will be more generic.

The order of the list of Attribute Set Index objects implies an order of precedence.

Example

1. A Feature contains a Data Quality object with fictional set to SE_TRUE. It also references an Attribute Set that contains a Data Quality object with fictional set to false. As a Feature may only contain one Data Quality object, the Data Quality object with fictional set to SE_TRUE is used, as it is contained directly by the Feature.

2. A Geometry contains two Property Table References and references an Attribute Set that contains another three. As a Geometry may contain many Property Table Reference objects, all five are used by the Geometry as required. The two that are contained directly are used first, then the three that are contained in the Attribute Set.

3. A Geometry contains two Image Mapping Functions and references an Attribute Set that contains another two. As a Geometry may contain many ordered Image Mapping Function objects, all four are used by the Geometry as required. The two that are contained directly are used in order first, then the three that are contained in the Attribute Set, again in order.

4. A Geometry contains two Property Table References and references two Attribute Sets. The first Attribute Set contains another Property Table Reference and the second Attribute Set contains another three Property Table References. As a Geometry may contain many Property Table Reference objects, all six would be used by the Geometry as required. The two that are contained directly would be used first, then the one that is contained in the first Attribute Set, and finally the three that are contained in the second Attribute Set.

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