You are hereXplain Meta Data ModelThe Xplain data dictionary is self-describing (meta data model). Its kernel contains three interrelated types, as shown below: The DDL statements are: base name (A40). base domain (A80). base kind (A14)= aggregation, specialisation. base role (A40). type type = name, representation. type attribute = composite_type, type, kind. type role attribute = [attribute], role. These data model definitions contain the relevant inherent constraints:
Aggregation and generalization abstractions are essential in semantic data models. The basic structure of the meta model confirms this. It consists of three interrelated types, with two relationships: between type and attribute and between attribute and role attribute. It is curious to see that the first concerns aggregation, the other generalization.
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