Class Name: Primitive Summary Item

Superclass - Base Summary Item

Definition

Used to specify common patterns of primitive objects that appear in a Model or under Environment Root. Each Primitive Summary Item represents an instance, or number of identical instances, of a class that appears in those parts of the transmittal that follow the pattern.

Primitive Summary Items can only represent objects of the Primitive Geometry and Primitive Feature types and subtypes, and also the types that may come beneath them in the hierarchy. They are combined together to form a hierarchy that mirrors the hierarchy of the objects that the Primitive Summary Items represent. This summary is actually a compressed form of the real hierarchy, as each Primitive Summary Item may represent a number of instances of that object type. Primitive Summary Item therefore has a multiplicity field, recording how many of the object type it actually represents. Note that all instances represented by one Primitive Summary Item must have exactly the same hierarchical pattern beneath them, right down to where the pattern summary finishes. In essence the Primitive Summary Item actually represents both the object instance and the specific hierarchy of objects underneath it.

Primary Page in DRM Diagram:

• 20

Secondary Pages in DRM Diagram:

• 1
• 2

Example

1. Summary of a common Polygon structure pattern within a Model. In this case, the pattern indicates that we can expect to see triangles. Note that other patterns can be present; in this particular example, the Model contains not only triangles, but other types of Polygons, such as quadrilaterals and even 5-sided Polygons. The Primitive Summary Items are just indicating common patterns; they're not enumerating all the patterns that are present.

FAQs

I'm consuming a transmittal in which the Environment Root's Primitive Summary Item shows a Polygon with 3 Vertices and an Image Mapping Function. Does this mean that all the terrain Polygons are triangles with Image Mapping Functions?

No. It just means that for this particular transmittal that's a common pattern for terrain Polygons.

Hey! The examples for SDRM Class Summary Item show Polygons and Vertices as SDRM Class Summary Items, but the examples for Primitive Summary Item show them as Primitive Summary Items! Isn't this ambiguous? What's going on?

This isn't ambiguous as the two classes (SDRM Class Summary Item and Primitive Summary Item summarize different aspects of a transmittal. Therefore the same classes can (and will) quite legitimately be represented by both. So Polygon and Vertex can turn up as types of SDRM Class Summary Items, to summarize their presence in the transmittal, and as Primitive Summary Items, to show common patterns of objects in which they are used.

Constraints

• Primitive Summary Item Type

Composed of (two-way)

• optionally, some Primitive Summary Items

Composed of (two-way metadata)(inherited)

• optionally, some EDCS Use Summary Items (notes)

Component of (two-way)

• optionally, an Environment Root
• optionally, some Primitive Summary Items
• optionally, a Model

Inherited Field Elements

Field Elements

Notes

Composed of Notes

EDCS_Use_Summary_Item

 Classification(s) used by an objects of the
 specified type, somewhere in the transmittal

Fields Notes

type

 The DRM class of the object represented by the summary item.

multiplicity

 the number of identical instances represented