The SEDRIS Data Representation Model
APPENDIX A - Classes
Hierarchy Summary Item
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Class Name: Hierarchy Summary Item
Subclasses
This DRM class is concrete and has no subclasses.
Definition
An instance of this DRM class represents an instance, or a number of
identical instances, of a <Geometry Hierarchy> instance or
<Feature Hierarchy> instance that exists within the
given <Model> instance or <Environment Root>
instance. <Hierarchy Summary Item> instances are combined
together to form hierarchies that mirror those that they summarize.
This summary is a compressed form of the actual hierarchy, as each
<Hierarchy Summary Item> instance may represent a number of
instances of the class indicated by its
drm_class field.
The multiplicity field records how many
instances of the given class a <Hierarchy Summary Item> instance
actually represents. All instances represented by one
<Hierarchy Summary Item> instance shall have exactly the same
hierarchical pattern beneath them, right down to where the
hierarchy summary concludes. A <Hierarchy Summary Item> instance
represents both the instance(s) that it describes, and the specific
hierarchy beneath it. It may have an optional association to the
<Geometry Hierarchy> instance(s) or
<Feature Hierarchy> instance(s) that it summarizes.
Each <Hierarchy Summary Item> instance can optionally have a
list of <EDCS Use Summary Item> components giving the
classifications that are attached to those instances in the transmittal
being summarized.
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 being summarized deems it of
potential use to consumers, the branches of the hierarchy summary
can terminate with a list of
<DRM Class Summary Item> components
representing the DRM objects beneath that point in the hierarchy.
Primary Page in DRM Diagram:
Secondary Pages in DRM Diagram:
Example
Consider an <Environment Root> instance for which the
geometry is to be summarized.
The geometry portion of the above <Environment Root> instance
can therefore be summarized as follows. Note that this is the same
<Environment Root> instance
as shown above, but for readability only the
<Hierarchy Summary Item> portion
of its instance diagram is shown here.
The <Hierarchy Summary Item> tree
depicted in ,
rooted at the <Environment Root> instance
depicted in ,
parallels the structure of the corresponding geometry. In this instance,
the data provider has elected not to provide a detailed summary of the
structure of the <Union Of Geometry Hierarchy> instance.
The list of <DRM Class Summary Item> components
merely identify classes that are somewhere below the
<Union Of Geometry Hierarchy>
instance, rather than the patterns in which they appear.
The <EDCS Use Summary Item> components summarize patterns of
ECCs, possibly used together with EACs, in the context being summarized.
If the data provider wished to summarize the hierarchy of the
<Union Of Geometry Hierarchy> instance in detail, its
<Hierarchy Summary Item> instance could be provided with
appropriate <Hierarchy Summary Item> components as desired,
until the summary reached the level of <Primitive Geometry>
instances and the hierarchy summary came to an end.
For examples of summaries of <Primitive Geometry> patterns,
see <Primitive Summary Item>.
FAQs
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If the intent is for a useful high level summary, why not just have
the consumer perform a shallow breadth-first search?
The consumer could indeed compute the information, since all that
this provides is a summary of what's in the transmittal. The reason
for providing the information is to indicate that users 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 providing
a top level summary, allows producers to 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
<Model> only have 0 - 2
<Hierarchy Summary Item>
components?
See
<<Hierarchy Summary Constraints>>.
Constraints
Associated to (one-way)
Composed of (two-way)
Composed of (two-way metadata) (inherited)
Component of (two-way)
Notes
Associated to Notes
If present, the association(s) to <Feature Hierarchy>
instances indicate that the <Hierarchy Summary Item>
instance summarizes the specific <Feature Hierarchy>
object tree(s) thus indicated.
If present, the association(s) to <Geometry Hierarchy>
instances indicate that the <Hierarchy Summary Item>
instance summarizes the specific <Geometry Hierarchy>
object tree(s) thus indicated.
Composed of Notes
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.
If present, the <DRM Class Summary Item> components of a
<Hierarchy Summary Item> instance list classes for which
instances occur beneath this point in the hierarchy being summarized.
If present, the <Hierarchy Summary Item> components of a
<Hierarchy Summary Item> instance summarize the next
level down in the component tree of the hierarchy being summarized.
Fields Notes
The drm_class
field indicates the DRM class of the DRM object(s)
represented by the
<Base Summary Item> instance.
The multiplicity_meaning field
specifies the meaning of the
multiplicity field value for the
<Hierarchy Summary Item> instance.
The multiplicity
field specifies the number of identical instances represented,
or the order of magnitude of that number, for the
<Hierarchy Summary Item>
instance. If the multiplicity is unknown, the value of this
field shall be set to zero.
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Last updated: August 23, 2005
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Copyright © 2005 SEDRIS™
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