16.4. Schema Abstraction Mechanisms
At times we might feel almost swamped by the level of detail captured on an ORM schema diagram, or even on a UML, ER, or relational schema. Nevertheless, such detail is important when developing, transforming, or mapping schemas. The ORM notation has been crafted to facilitate these tasks. As we’ve seen, the diagrams may be verbalized naturally and populated with fact instances, their object-role-based notation allows many constraints to be expressed intuitively, and their object types reveal the semantic domains that glue the schema together. All of this helps the modeler to get a complete and correct picture, and to transform the model in a rigorous way with formal control of information loss or gain.
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