Pit-koon Teo Data Resources
نویسندگان
چکیده
A 3-level schema architecture is proposed to address some inadequacies in recent object-oriented data models. The conceptual schema is based on a normal form object-oriented entityrelationship IOOER) diagram. A set of mapping rules is defined that allows 00 externalschemas, based on the 02 data model, to be generated from the conceptual schema. Similar mapping rules can be defined to generate external schemas for other 00 data models. Other features of this model include the incorporation of derived attributes, deductive rules, triggers and methods. proposed 00 data models [3,6,7,17 etc]) is treated as an external schema that is generated from the conceptual schema by applying a set of mapping rules. Distinct sets of mapping rules are needed to handle different 00 data models. Each 00 database schema is, therefore, a view of the conceptual schema. User applications (00 or otherwise) can then be written based on the 00 external schemas that are generated from the conceptual schema. The advantages of the 00 approach are therefore preserved at the external schema level. To illustrate our approach, a set of mapping rules is defined in this paper to generate, as examples, 02 class definitions from a normal form OOER diagram. Similar mapping rules can be defined for other 00 data models.
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تاریخ انتشار 2000