Class Name: Primitive Summary Item

Superclass - <Base Summary Item>

Subclasses

Definition

An instance of this DRM class specifies a common pattern of primitive objects that appear in the scope being summarized, which may be either a <Model> instance or an <Environment Root> instance. A <Primitive Summary Item> instance represents one or more instances of the class specified by its drm_class field that conform to the specified pattern.

A <Primitive Summary Item> instance may represent only instances of <Primitive Geometry>, <Primitive Feature>, their subclasses, and the classes that may appear in their component trees. <Primitive Summary Item> instances are combined to form a hierarchy mirroring that of the primitive instances that they represent, such that the summary is a compressed form of the actual hierarchy.

Since a <Primitive Summary Item> instance may represent many instances of the primitive that it summarizes, it has a multiplicity field, indicating how many instances of the pattern it represents. Note that all instances represented by a given <Primitive Summary Item> instance shall conform exactly to that pattern, up to the point where the summary's pattern ceases to provide specifics.

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 a data consumer 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 <Polygon> instances, such as quadrilaterals and even 5-sided <Polygon> instances. The <Primitive Summary Item> instances are just indicating common patterns; they're not enumerating all the patterns that are present.

   

FAQs

Suppose that as a consumer, I encounter a <Primitive Summary Item> as a component of an <Environment Root>, which specifies a pattern of usage for instances of a given class. Does this mean that all instances of that class in the scope of the given <Environment Root> shall comply with the specified pattern?

No; it only indicates that in this particular scope, the specified pattern is very common.

For instance, consider an <Environment Root> with a <Primitive Summary Item> describing a texture-mapped triangular <Polygon> - that is, a <Polygon> with an <Image Mapping Function> component and 3 <Vertex> components. All that this means is that <Polygon> instances of that description are common in the scope of that <Environment Root>.

Can a given class' usage be simultaneously and unambiguously summarized by a <DRM Class Summary Item> and a <Primitive Summary Item> in the same scope?

Yes, because <DRM Class Summary Item> and <Primitive Summary Item> summarize different aspects of usage. <DRM Class Summary Item> summarizes the presence of instances of the specified class, while <Primitive Summary Item> represents common patterns of objects in which instances of the specified class appear.

Constraints

• <<Publishable Object>>
• <<Primitive Summary Item Constraints>>

Composed of (two-way)

• zero or more <Primitive Summary Item> instances

Composed of (two-way metadata) (inherited)

• zero or more <EDCS Use Summary Item> instances (notes)

Component of (two-way)

• zero or one <Environment Root> instance
• zero or one <Model> instance
• zero or more <Primitive Summary Item> instances

Inherited Field Elements

Field Elements

Notes

Composed of Notes

EDCS_Use_Summary_Item

 If present, the list of <EDCS Use Summary Item> components of
 a <Base Summary Item> instance summarize EDCS usage by instances
 of the class specified by drm_class that occur somewhere in
 the scope being summarized.

Fields Notes

drm_class

 The drm_class field indicates the DRM class of the object(s)
 represented by the given <Base Summary Item> instance.

multiplicity

 The multiplicity field indicates the number of identical instances
 represented.