The SEDRIS Data Representation Model
APPENDIX A - Classes
Spatial Index Related Feature Topology

Class Name: Spatial Index Related Feature Topology

Superclass - <Feature Topology Hierarchy>

Subclasses

This DRM class is concrete and has no subclasses.

Definition

An instance of this DRM class specifies a spatially indexed related aggregation representing a collection of primitive <Feature Topology> instances.

Primary Page in DRM Diagram:

Secondary Pages in DRM Diagram:

This class appears on only one page of the DRM class diagram.

Example

  1. An <Aggregate Feature> instance can have more than one spatial related organization for its topology. In a given transmittal, the top <Aggregate Feature> instance under an <Environment Root> instance has a single 10 kilometre by 10 kilometre spatial related organization of topology spanning the entire transmittal, as well as a single 500 metres by 500 metres spatial related organization of topology also spanning the entire transmittal. That top <Aggregate Feature> instance has two <Spatial Index Related Feature Topology> components, one for the 10 kilometre squares and one for the 500 metre squares.

FAQs

Why an aggregate object instead of a hierarchy or some other type of DRM object?

We need a 'branch', and each branch from an aggregation is a hierarchy object, because <Aggregate Feature> instances contain <Feature Hierarchy> instances. When an <Aggregate Feature> instance has a <Feature Topology Hierarchy>, that <Aggregate Feature> represents a distinct topological surface. We shall organize a topological surface, a.k.a. an "independent topology", which eventually, in the DRM, is 'rooted at' a single <Aggregate Feature> instance.

The <Feature Hierarchy> instances are either <Aggregate Feature>s or <Feature Model Instance>s. The topological organization of the <Model>, if any, is contained within the <Model>, so we're left with a need to specify the topological organization of an <Aggregate Feature> instance. The organizing principle shall be applied at the <Aggregate Feature> instance level - no lower, no higher.

The same spatial indexing structure can be shared by multiple <Aggregate Feature> instances, because there can exist multiple organizations of the same set of <Feature Representation> instances. When a single set of <Feature Representation> instances is organized by multiple classification approaches, it is still the same set of <Feature Representation> instances being dealt with, and still the same set of <Feature Node> instances, <Feature Edge> instances, and <Feature Face> instances. Changing the logical organization of the <Feature Representation> instances has no effect on the spatial organization of the underlying topological primitives. Thus, one spatial organization for a set of topological primitives may be shared by many different organizations (aggregations) of <Feature Representation> instances, where the <Feature Representation> instances are composed of the same spatially organized topological primitives, regardless of the organization from which the <Feature Representation> instances are viewed.

Constraints

Composed of (two-way)

Component of (two-way) (inherited)

Inherited Field Elements

SE_Feature_Topology_Level feature_topology_level; 2

Field Elements

SE_Boolean sparse; 3
SE_Integer_Positive column_count; 4
SE_Integer_Positive row_count; 5
SE_Long_Float column_width; 6
SE_Long_Float row_width; 7
SE_Spatial_Index_Spacing_Unit spacing_unit; 8

Notes

Composed of Notes


Location

The <Location> component is the origin of the collection, which is the lower left corner.

Fields Notes

feature_topology_level

The feature_topology_level field specifies the level of feature topology that is present within the hierarchy represented by the <Feature Topology Hierarchy> instance.

sparse

If the value of the sparse field is SE_FALSE, all column and row entries are present; otherwise one or more entries are not present.

column_count

The column_count field specifies the number of cells along the primary axis.

row_count

The row_count field specifies the number of cells along the secondary axis.

column_width

The column_width field specifies the length of a cell in the given unit along the primary axis.

row_width

The row_width field specifies the length of a cell in the given unit along the secondary axis.

spacing_unit

The spacing_unit field specifies the unit of measurement for column_width and row_width.


Prev: Spatial Index Data. Next: Spatial Index Related Features. Up:Index.

Last updated: July 26, 2006 Copyright © 2006 SEDRIS