12 Jun 2006 - GML and ebRIM

One view of GML is as a metadata framework. When combined with the ebRIM (e-business registry information model) this capability is further strengthened. ebRIM is one of the key specifications from OASIS. It provides a general data model for metadata management. It is also the basis of the WRS or ebRIM profile of the OGC Catalogue 2.0 specification. ebRIM provides a rich set of features including:

• user defined classification scheme or taxonomies
• user defined associations
• life cycle metadata
• audit trail

These features are supported throuigh the e-business registry information model which provides a class hierarchy including RegistryObject, RegistryPackages, ExtrinsicObject, Classification, ClassificationNode, and Association. ebRIM also provdies the concept of Registry and Repository, with the ExtrinsicObjects of the Registry acting as proxies for items in a Repostory associated to the Registry. In this note we outline the use of ebRIM in relation to GML. The basic idea is to create a set of ebRIM objects that correspond to the GML core object types including feature, coverage, observation, coordinate reference system, and unit of measure definition. This approach allows ebRIM to provide an logical model of the GML type hierarchy. The root of the GML object hierarchy gml:_GML is represented in our ebRIM model by GMLObject, as subtype of ebRIM RegistryObject. We choose this since GMLObject cannot be instantiated and hence cannot have a corresponding repository item. All other GML objects in our model are then derived from this GMLObject, including Feature, CRS, and UofM, valueObject. Subtypes of Feature, namely Coverage, Observation and DynamicFeature. Other deeper objects are not represented in this model (some will argue that they should be) since they are typically used to describe the more "primary" objects identified above. Each of the primary objects identified in our model are mapped to a repository item. This is in effect the meaning of "Extrinsic" in ExtrinsicObject. The repository item is then typically a GML core schema fragment. With this more logical model one can readily publish GML application schemas and other encodings (e.g. UML models) from this ebRIM representation. It can also provide the basis for feature catalogues, image catalogues and others. This will be discussed in greater detail in upcoming blogs. It will also provide the basis for advanced treatment of GML schema components, liberating them from the current notion of schema files. More on this later …

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