Class Name: Hierarchy Summary Item

Superclass - Base Summary Item

Definition

Used as part of a summary of the hierarchical structure beneath Environment Root or within a Model. A Hierarchy Summary Item represents an instance, or number of identical instances, of a class that exists within the Model or under Environment Root.

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

Each Hierarchy Summary Item can have an optional association to the Geometry Hierarchy(ies) or Feature Hierarchy(ies) that it summarizes.

Each Hierarchy Summary Item (i.e. each object type) can optionally have a list of EDCS Use Summary Items giving the classifications that are attached to those instances in the transmittal.

The Hierarchy Summary does not have to be a total representation of the entire transmittal hierarchy and can be limited to a useful high level summary.

If the producer of the transmittal deems it of potential use to consumers, the branches of the Hierarchy Summary can terminate with a list of SDRM Class Summary Items representing the objects beneath that point in the hierarchy.

Primary Page in DRM Diagram:

• 20

Secondary Pages in DRM Diagram:

• 1
• 2
• 3
• 8

Example

1. A hierarchy summary of the content of Environment Root.

        Environment <>---------------- Hierarchy
           Root                        Summary Item
            <>            +----------- (LoDRG, 1)
             |            |                 <>
             |            |                  |
           LoDRG ---------+           +------+---------+
            <>                        |                |
             |                   Hierarchy         Hierarchy
      +------+-------+           Summary Item     Summary Item
      |      |       |            (UoPG, 2)        (UoGH, 1)
    UoPG   UoPG    UoGH<>--CD        <>             <>
     <>     <>      <>                |              |
      |      |       |                |              +-- EDCS Use Summary Item
      |      |       |                |              |
      |      |       |                |              |
      |      |       |            Primitive          +-- Hierarchy
    Polys Polys  +---+----+      Summary Item           Summary Item
      .      .   |        |       (Polygon)              (UoPG, 2)
      .      . UoPG     UoPG         <>                     <>
                <>       <>          |                       |
                 |        |       Primitive              Primitive
               Polys    Polys    Summary Item          Summary Item
                 .        .        (Vertex)              (Polygon)
                 .        .                                <>
                 .        .                                 |
                                                          Primitive
                                                        Summary Item
                                                         (Vertex)
   

FAQs

If the intent is for a useful high level summary, why not just do a shallow breadth-first search?

Indeed you could, since all we're doing here is summarizing what's in the transmittal. The reason for giving the information is to tell people that they don't have to be exhaustive if they don't think it's appropriate/required/necessary, or a good use of processing time, etc. Even just giving a top level summary, however, allows producers to do just that, i.e. summarize. They don't have to be complete in a legalistic way, and can therefore use this mechanism to summarize the major hierarchical structuring, perhaps leaving out less significant deviations from that predominant pattern. These would turn up in a search and actually confuse the issue. If you like, this mechanism allows a producer to sketch out the forest without missing it for the trees.

Why can Environment Root and Models only have 0-2 Hierarchy Summary Item components?

Environment Root and Models do not have to have a hierarchy summary (i.e. 0). If they do want a summary of hierarchy then they can have one summary for Geometry (i.e. 1), one summary for Features (i.e. 1), or a summary of each (i.e. 2).

Constraints

• Non Crossing Associations
• Non Overlapping SDRM Class Summary Items

Associated to (one-way)

• optionally, some Feature Hierarchies
• optionally, some Geometry Hierarchies

Composed of (two-way)

• optionally, some Hierarchy Summary Items
• optionally, some SDRM Class Summary Items (notes)

Composed of (two-way metadata)(inherited)

• optionally, some EDCS Use Summary Items (notes)

Component of (two-way)

• optionally, an Environment Root
• optionally, some Hierarchy 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

SDRM_Class_Summary_Item

 Represents a list of classes that occur
 beneath this point in the hierarchy

Fields Notes

type

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

multiplicity

 the number of identical instances represented,
 or the order of magnitude of that number;
 (if the multiplicity is unknown, should be set to zero)