The SEDRIS Data Representation Model
APPENDIX B - Constraints
Quad Tree Related Organizing Principle

Definition

For any quad tree-related organization QTRA, whether a <Quad Tree Related Features> or a <Quad Tree Related Geometry>,

  1. QTRA shall have a <Spatial Domain>.

  2. Each branch of QTRA shall comply with the following constraints.
    2.1 Each component representing a quadrant shall have a <Spatial Domain> component. In the case of quadrants represented by <Geometry Model Instance> or <Feature Model Instance> instances, the <Model> being referenced shall have the <Spatial Domain>.
    2.2 The regions defined by the branches shall not overlap; that is, the <Spatial Domain> components of the component hierarchies shall not overlap.
    2.3 The four possible quadrant components' <Spatial Domains> shall be defined in their native SRF within the area specified by the QTRA's <Spatial Domain> as follows.

    Quad Tree Related Organizing Principle: Quadrant Specification

    Consider the bounding area defined by the <Spatial Domain> of QTRA, as divided into 4 quadrants of equal size.

    2.3.1 If a branch with SE_QUADRANT_NORTHWEST is present, its <Spatial Domain> shall specify the area of the northwest quadrant, such that
    2.3.1.1 its eastern boundary aligns with the western boundary of the SE_QUADRANT_NORTHEAST quadrant's <Spatial Domain>, if present, and
    2.3.1.2 its southern boundary aligns with the northern boundary of the SE_QUADRANT_SOUTHWEST quadrant's <Spatial Domain>, if present.
    2.3.2 If a branch with SE_QUADRANT_NORTHEAST is present, its <Spatial Domain> shall specify the area of the northeast quadrant, such that
    2.3.2.1 the <Location> instance representing its northeast corner corresponds to that of QTRA's <Spatial Domain>,
    2.3.2.2 its western boundary aligns with the eastern boundary of the SE_QUADRANT_NORTHWEST quadrant's <Spatial Domain>, if present, and
    2.3.2.3 its southern boundary aligns with the northern boundary of the SE_QUADRANT_SOUTHEAST quadrant's <Spatial Domain>, if present.
    2.3.3 If a branch with SE_QUADRANT_SOUTHWEST is present, its <Spatial Domain> shall specify the area of the southwest quadrant, such that
    2.3.3.1 the <Location> instance representing its southwest corner corresponds to that of QTRA's <Spatial Domain>,
    2.3.3.2 its eastern boundary aligns with the western boundary of the SE_QUADRANT_SOUTHEAST quadrant's <Spatial Domain>, if present, and
    2.3.3.3 its northern boundary aligns with the southern boundary of the SE_QUADRANT_NORTHWEST quadrant's <Spatial Domain>, if present.
    2.3.4 If a branch with SE_QUADRANT_SOUTHEAST is present, its <Spatial Domain> shall specify the area of the southeast quadrant, such that
    2.3.4.1 its western boundary aligns with the eastern boundary of the SE_QUADRANT_SOUTHWEST quadrant's <Spatial Domain>, if present, and
    2.3.4.2 its northern boundary aligns with the southern boundary of the SE_QUADRANT_NORTHEAST quadrant's <Spatial Domain>, if present.

  3. The strict_organizing_principle and unique_descendants field values of QTRA shall be SE_TRUE.

Rationale

  1. The quad tree-related organization shall provide a <Spatial Domain>, so that the data provider specifies the bounding area that the quad tree is dividing into quadrants.
  2. Each component representing a quadrant shall specify a <Spatial Domain>, because although quadrants are intended to be of equal size, "size" is not invariant under coordinate transformation. The <Spatial Domains> are necessary to ensure that the boundaries between quadrants are well-defined when coordinate conversions and transformations are applied.
  3. The <Spatial Domain> instances of the branches and the quadrants that they represent shall correspond.

Example

No Example supplied.

FAQs

No FAQs supplied.
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Last updated: October 1, 2002 Copyright © 2002 SEDRIS™