Epicentre V3.0 Status

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Epicentre V3.0Status

• Houston
• 7 December 1999

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Why Restructure

• The Spatial Model is inconsistent.
• The model is unnecessarily complex
• multiple inheritance
• inconsistent attributes
• redundant capabilities

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Restructuring Goals

• To fix the spatial model.
• To eliminate unnecessary multiple inheritance
  without loss of semantics.
• To simplify the model where reasonable.
• To remove inconsistencies.
• To add identified fixes and enhancements.
• To make the changes more visible by utilizing
  Incremental EXPRESS.

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Spatial Model Problems

• Mixture of two paradigms (since V2.0)
• An object is represented by a spatial object
  (V1.0).
• Each spatial object represents one opinion.
• Each geometry property is a representation of
  that opinion.
• An object is a spatial object (V1.1).
• Some geometry properties represent an opinion
• Some geometry properties are an alternative
  representation of an opinion.

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Spatial Complexity
Yellow fill - Identifier attribute Blue fill -
Name attribute Red fill - No attribute Cross
hatch - Mandatory attribute Colored line -
Recommended deletion
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Resulting Hierarchy
Contains only entities which remain from previous
slide. Green fill indicates a new entity
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Resulting Behavior
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Material and Feature Complexity
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Resulting Hierarchy
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Merged Hierarchy
Contains only entities which remain from the two
problem hierarchies. Green fill indicates a new
entity
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Identifier Cleanup

• Change all attributes such as name and kind
  to be identifier.
• Make all identifiers 80 characters (instead of 40
  or 50 or 80).
• Where possible, move the identifiers from the
  leaf entities up to a supertype (e.g., Ref_code).
  The restructuring made this much easier.

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Other Cleanup

• 10 Alias entities replace 25 entities with much
  broader scope.
• All entities have description attribute.
• Eliminate many-to-many relationships.
• Add missing inverse relationships.

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New Hierarchy
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New Changes

• Drop all Activity subtypes and generalize
  behavior at supertype level.
• Drop most Temporal Object subtypes and generalize
  behavior at supertype level.
• Add EPSG recommendations for Coordinate Systems.
• Include many SLEGGE proposals.
• To date, there is a net reduction of 300
  entities with increased functionality.

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New Activity Behavior
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Expected Activity Involvement
An activity which is a member of a class may
commonly have an involvement with an instance of
an entity. The involvement maybe constrained
based on membership in a class.
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Expected Activity Property
An activity which is a member of a class may
commonly have a property of a particular kind.
Renamed from Pty_equipment_facility
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Expected Activity Composition
An activity which is a member of a class may
commonly be composed of activities which are
members of a particular class.
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Major EPSG Recommendations

• Allow for a Compound Coordinate System (I.e., 2D
  1D).
• Allow for a Concatenated Transformation (I.e., an
  ordered list of transformations).

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Epicentre V3.alpha

• Available at http//www.posc.org under
  Technical then Future Release Version 3.0.
• Online viewable _at_ http//w3.posc.org/Epicentre_V3a
  lpha/DataModel/main.html
• Downloadable zip file (5.7MB).
• Logical Model Files
• Express Files
• Change Files

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Incremental EXPRESS

• Syntax for machine and human readable changes to
  EXPRESS files.
• POSC is developing tools which apply the changes
  and create a new EXPRESS file and documentation.
• POSC web site for registering change files and
  for applying the changes to create a new schema
  version.
• http//w3.posc.org/IncrExpress/