The SEDRIS Data Representation Model
APPENDIX A - Classes
Ellipse

Class Name: Ellipse

Superclass - <Surface Geometry>

Subclasses

This DRM class is concrete and has no subclasses.

Definition

An instance E of this DRM class specifies a closed plane curve such that for each point P on the curve, the sum of P's distances from two fixed points (called the foci of E) is a constant. The <Location> component of E specifies the centre of the instance E.

The line passing through the foci of E is termed the major axis of E. The direction of the major axis of E is specified by the <Reference Vector> component of E with vector_type = SE_REFVEC_MAJOR_AXIS.

The line passing through the centre of E and perpendicular to the major axis of E is termed the minor axis of E. The direction of the minor axis of E is specified by the <Reference Vector> component of E with vector_type = SE_REFVEC_MINOR_AXIS.

Primary Page in DRM Diagram:

Secondary Pages in DRM Diagram:

Example

  1. The physical extent of certain underwater acoustic phenomena are best described by <Ellipse> instances in some cases, and by <Volume Object> instances in others.

FAQs

Why doesn't the DRM have a Circle class?

Because a circle is a special case of an ellipse for which the major and minor axes have the same length.

Constraints

Associated with (two-way)

Composed of (two-way) (inherited)

Composed of (two-way)

Composed of (two-way metadata) (inherited)

Component of (two-way) (inherited)

Inherited Field Elements

This class has no inherited field elements.

Field Elements

SE_Long_Float major_axis_length; 5
SE_Long_Float minor_axis_length; 6

Notes

Associated with Notes


Geometry_Node

The <Geometry Node> instance corresponds to the centre of the <Ellipse> instance.

Composed of Notes


Union_Of_Primitive_Geometry

A <Primitive Geometry> instance P has a <Union Of Primitive Geometry> component only when P can be decomposed into nested <Primitive Geometry> instances.

EXAMPLE  A <Polygon> instance can be decomposed into multiple <Polygon> instances representing subfaces.


Location

The <Location> component is the location of the centre of the <Ellipse> instance.


Reference_Vector

For a given <Ellipse> instance, one <Reference Vector> component shall have vector_type = SE_REFVEC_MAJOR_AXIS, the other shall have vector_type = SE_REFVEC_MINOR_AXIS, and the two shall be mutually perpendicular.

Fields Notes

major_axis_length

The major_axis_length field is specified in metres.

minor_axis_length

The minor_axis_length field is specified in metres.


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Last updated: July 26, 2006 Copyright © 2006 SEDRIS