Definition

<Geometry> or <Feature> instances may contain attribute and / or meta data objects and also <Attribute Set Index> instances 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> instances. 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> instances 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> instance in the list are then used, in order. Then those contained in the <Attribute Set> referenced by the second <Attribute Set Index> instance 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> instances implies an order of precedence.

Example

1. A <Feature> contains a <Data Quality> instance with fictional set to SE_TRUE. It also references an <Attribute Set> that contains a <Data Quality> instance with fictional set to SE_FALSE. As a <Feature> may contain only one <Data Quality> instance, the <Data Quality> instance 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> instances, 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> instances, 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> instances, 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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