Definition

Associations shall not cross <Models> and/or <Environment Root>, except for <Geometry Model Instance> to <Geometry Model>, and <Feature Model Instance> to <Feature Model>.

Rationale

Consider the <Feature> with <Geometry Hierarchy> association. This association means that the <Feature> is an alternate representation of the <Geometry Hierarchy>. A terrain <Feature> represents some part of the terrain, not a part of some <Model>; a <Model> feature represents some abstraction of the <Model> rather than a feature of the terrain.

Example

1. Consider a transmittal with an <Environment Root> and <Model Library>. Let "F15" be a <Model> in the <Model Library>, under which we have <Polygons>. No <Feature> under the <Environment Root> may associate with an "F15" <Polygon>, since a terrain <Feature> cannot at the same time represent a generic "F15" <Polygon>.

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