|
The SEDRIS Data Representation Model
APPENDIX A - Classes Feature |
|---|
An instance of this DRM class represents an entity in the environment (or a hierarchical collection of such entities) so as to abstract away all spatial information that is not needed to reason about that entity in terms of its spatial connectivity.
A wide variety of spatially located entities, including roads, railroads, streams, rivers, lakes, bridges, buildings, built-up areas, forests, fields, political boundaries, powerlines, airfields, etc. can be abstractly represented as <Feature> instances. <Feature> instances may be organized into thematic layers, each forming a separate topological surface.
No. <Feature>s are conceptual entities. There are no limits on the size of a single feature, and very few limits on what can be considered to be a single feature. For example, the entire Interstate highway system could be considered to be a single high-level feature, if that were useful in a particular context. However, there are some limits on individual <Primitive Feature> objects.
An association between two <Feature> instances indicates that they are alternate representations of the same environmental object.
An association between a <Geometry Hierarchy> instance and a <Feature> instance indicates that the <Geometry Hierarchy> and the <Feature> are alternate representations of the same environmental object.
An association between a <Property Grid> instance and a <Feature> instance indicates that the <Feature> and the <Property Grid> (or some specific cell data within that <Property Grid>) are alternate representations of the same environmental object. Each associated <Property Grid> will indicate which is the case.
|