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The MDC-OIM Database Schema is a metamodel describing relational data sources. Just as with CWM, the purpose of the relational
metamodel is to provide a means by which tools may exchange commonly-understood descriptions of relational schemas, with the
possible inclusion of tool-specific extensions. It is modeled largely after the ANSI SQL-92 standard. Here are the major comparison
points between the CWM Relational Package and the OIM Database Schema:
• Reference standards. OIM is based on the SQL-92 standard, while CWM is based on the SQL-99 standard and is compatible with JDBC.
• Base metaclasses. Both OIM and CWM have fairly similar base metaclass structures, centered on the notion of column set and the subsequent derivation of table, view, and query from the column set.
• Catalog and schema. Both the CWM and OIM relational models support the basic structure of catalogs containing schemas and schemas, in turn, containing all other relational objects.
• Deployment structures. The OIM generally provides Logical and Deployment subclasses of all of its major semantic classes throughout the OIM Database Schema. For example, LogicalTable and DeployedTable both derive from the (semantic) Table metaclass. However, these Logical and Deployed subclasses are generally not defined much further, except DeployedCatalog is represented as being owned by a DataSource, which in turn has associations with metaclasses representing Connections and Providers. Note that most of the OIM models derive from the Database Schema model; hence, the ultimate deployment of any part of the OIM must be via mappings to the Database Schema (relational) metamodel. The overall deployment structures of the CWM metamodel, by comparison, are much more general than this. CWM defines a Software Deployment metamodel that defines concepts of providers, data managers, and connections. Any logical data model (whether Relational, Multidimensional, Record) models its own deployment by mapping to an appropriate metaclass of the CWM Software Deployment package. For example, the Catalog metaclass of the CWM Relational metamodel is implicitly owned by the DataManager metaclass of the Software Deployment metamodel, and this metamodel in turn relates the physical DataManager to its associated DataProviders, ProviderConnections, Machine, Site, and most importantly, deployment-specific TypeMappings (which in turn derive from the CWM Foundation package).
• Keys and indexes. The concepts of keys (unique keys, foreign keys) and indexes are defined in the CWM as CWM Foundation metaclasses, so they have general applicability to other data models within the CWM, not just the CWM Relational
Package. OIM confines keys and indexes to its relational schema. Hence, only OIM data source models that derive from, or are based on, the Database Schema, can provide these concepts.