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Database abstractions: aggregation and generalization

Database abstractions: aggregation and generalization,10.1145/320544.320546,ACM Transactions on Database Systems,John Miles Smith,Diane C. Pirog Smith

Database abstractions: aggregation and generalization   (Citations: 796)
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Two kinds of abstraction that are fundamentally important in database design and usage are defined. Aggregation is an abstraction which turns a relationship between objects into an aggregate object. Generalization is an abstraction which turns a class of objects into a generic object. It is suggested that all objects (individual, aggregate, generic) should be given uniform treatment in models of the real world. A new data type, called generic, is developed as a primitive for defining such models. Models defined with this primitive are structured as a set of aggregation hierarchies intersecting with a set of generalization hierarchies. Abstract objects occur at the points of intersection. This high level structure provides a discipline for the organization of relational databases. In particular this discipline allows: (i) an important class of views to be integrated and maintained; (ii) stability of data and programs under certain evolutionary changes; (iii) easier understanding of complex models and more natural query formulation; (iv) a more systematic approach to database design; (v) more optimization to be performed at lower implementation levels. The generic type is formalized by a set of invariant properties. These properties should be satisfied by all relations in a database if abstractions are to be preserved. A triggering mechanism for automatically maintaining these invariants during update operations is proposed. A simple mapping of aggregation/generalization hierarchies onto owner-coupled set structures is given.
Journal: ACM Transactions on Database Systems - TODS , vol. 2, no. 2, pp. 105-133, 1977
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    • ...But what exactly are association patterns? Closely related to association patterns are the proposed and varied characteristics and notations for describing the semantics of certain types of relationships: the weak entity type in the Entity-Relationship (ER) model [5], the generalization/specialization relationship in semantic and object models [27], the properties ascribed to whole-part relationships, e.g., [1,3,24,29], and the shared ...

    Bryon K. Ehlmann. Association patterns for data modeling and definition

    • ...Numerous extensions to the ER notation have been defined, notably extensions of cardinality constraints [23,24] extensions that deal with time and history [25,26], extensions with aggregation structures [27,28,29,30,31] and, more recently, sets [32], and extensions with taxonomic structures [27,33,34,35]...
    • ...Numerous extensions to the ER notation have been defined, notably extensions of cardinality constraints [23,24] extensions that deal with time and history [25,26], extensions with aggregation structures [27,28,29,30,31] and, more recently, sets [32], and extensions with taxonomic structures [27,33,34,35]...

    Roel Wieringa. Real-World Semantics of Conceptual Models

    • ...142 N. Roussopoulos and D. Karagiannis and Smith [SS77]...

    Nick Roussopouloset al. Conceptual Modeling: Past, Present and the Continuum of the Future

    • ...Generalization/specialization types are considered fundamental modeling constructs [3, 21]...
    • ...In terms of constraints, a generalization type can be: total and disjoint (t, d); partial and disjoint (p, d); total and overlapping (t, o); or partial and overlapping (p, o) [21]...

    Rebeca Schroederet al. Designing XML documents from conceptual schemas and workload informati...

    • ...The choice of the details to omit is made by considering both the intended application of the abstraction and also its users [11]...
    • ...Generalisation refers to an abstraction in which a set of similar elements is regarded as a generic element [11]...

    Veronica Gacitua-decaret al. Automatic Business Process Pattern Matching for Enterprise Services De...

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