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

Class Name: Spatial Index Related Geometry

Superclass - <Aggregate Geometry>

Subclasses

This DRM class is concrete and has no subclasses.

Definition

An instance of this DRM class specifies an aggregation of <Geometry Hierarchy> objects in which each component <Geometry Hierarchy> represents a different tile within a spatially indexed (tiled) organization of <Primitive Geometry> objects within a SEDRIS transmittal. The <Spatial Index Data> link object attached to each component <Geometry Hierarchy> indicates the tile that it represents.

Primary Page in DRM Diagram:

Secondary Pages in DRM Diagram:

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

Example

  1. See <<Spatial Index Organizing Principle>>, example #1.

  2. Consider an <Environment Root> describing a terrain surface that is a mix of grids and polygons, organized by spatial indexing into 9 cells.

    A B C
    D E F
    G H I

    All cells except H are grids (represented in SEDRIS as <Property Grid> instances) captured at 1 level of detail. Cell H consists of <Polygon> instances.

    Spatial Index Related Geometry, Example 1

    Please note that the components of the <Spatial Index Related Geometry> are not ordered; the <Spatial Index Data> is used to identify the individual tiles.

FAQs

What is the purpose of this class?

This class allows <Geometry Representation> instances to be organized (tiled) according to some spatial index.

Consider a data provider whose data consists of terrain <Polygon> instances that are tiled along the lines of a grid, but in which some <Polygon> instances here and there cross over tile boundaries. Can these <Polygon> instances be organized with a <Spatial Index Related Geometry> instance?

Yes, if its strict_organizing_principle is set to SE_FALSE to indicate that the indexing is not strictly followed (see <<Spatial Index Related Organizing Principle>>, example #1). Each tile of the spatial index would be represented by a <Geometry Hierarchy> component of the <Spatial Index Related Geometry> instance.

Where is the origin of the spatial index?

The required <Location> component of a <Spatial Index Related Geometry> instance specifies the origin of the spatial index, which is its lower-left corner.

Constraints

Associated to (one-way) (inherited)

Associated by (one-way) (inherited)

Composed of (two-way) (inherited)

Composed of (two-way)

Composed of (two-way metadata) (inherited)

Component of (two-way) (inherited)

Inherited Field Elements

SE_Boolean unique_descendants; (notes)
SE_Boolean strict_organizing_principle; (notes)

Field Elements

SE_Boolean sparse; (notes)
SE_Integer_Positive column_count; (notes)
SE_Integer_Positive row_count; (notes)
SE_Long_Float column_width; (notes)
SE_Long_Float row_width; (notes)
SE_Spatial_Index_Spacing_Unit spacing_unit; (notes)

Notes

Associated to Notes


Feature_Representation

 An association between a <Feature Representation> instance
 and a <Geometry Hierarchy> instance indicates that the
 environmental object(s) that they represent have the
 semantic relationship indicated by the <Base Association Data>
 instance on the association relationship.

Geometry_Hierarchy

 An association between two <Geometry Hierarchy> instances
 indicates that the environmental object(s) that they
 represent have the semantic relationship indicated by
 the <Base Association Data> instance on the association
 relationship.

Associated from Notes


Feature_Representation

 An association between a <Feature Representation> instance
 and a <Geometry Hierarchy> instance indicates that the
 environmental object(s) that they represent have the
 semantic relationship indicated by the <Base Association Data>
 instance on the association relationship.

Geometry_Hierarchy

 An association between two <Geometry Hierarchy> instances
 indicates that the environmental object(s) that they
 represent have the semantic relationship indicated by
 the <Base Association Data> instance on the association
 relationship.

Hierarchy_Summary_Item

 An association from a <Hierarchy Summary Item> instance to a
 <Geometry Hierarchy> indicates that the <Hierarchy Summary Item>
 summarizes that <Geometry Hierarchy>.

Reference_Surface

 An association from a <Reference Surface> instance to a
 <Geometry Hierarchy> indicates that the <Geometry Hierarchy>
 organizes the geometric objects that specify the resolution
 surface of the <Reference Surface>.

Composed of Notes


Collision_Volume

 In the case where multiple <Collision Volume> components are
 specified for a given <Aggregate Geometry>, the union of the
 volumes thus specified is used in collision detection.

Location

 This is the origin of the collection, which is the lower-left corner.

Fields Notes


unique_descendants

 If the value of the unique_descendants field is SE_TRUE, each
 descendant of this aggregation,
 that is, each <Geometry Representation> instance that exists
 in the component tree
 rooted at the given <Aggregate Geometry>, shall be unique, in the
 sense that it shall appear in only one branch of this aggregation.
 If unique_descendants is SE_FALSE, at least one
 <Geometry Representation> instance
 appears in more than one branch of the aggregation.

strict_organizing_principle

 If the value of the strict_organizing_principle field is SE_TRUE,
 each branch of this aggregation
 strictly complies with the organizing principle for its
 particular subclass. If this value is SE_FALSE, at least
 one branch does not strictly comply with the given
 organizing principle. See the organizing principle constraint
 for each specific subclass for details.

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

 This is the number of cells along the X axis.

row_count

 This is the number of cells along the Y axis.

column_width

 This is the length of a cell in the given unit along the X axis.

row_width

 This is the length of a cell in the given unit along the Y axis.

spacing_unit

 This is the unit of measurement used for the spacing of the
 spatial index.
Prev: Spatial Index Related Features. Next: Spatial Index Related Geometry Topology. Up:Index.

Last updated: July 16, 2004 Copyright © 2004 SEDRIS™