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Dissertation
An analysis of ternary relationships in entity-relationship modeling
Doctor of Philosophy (Ph.D.), Drexel University
Jun 1995
DOI:
https://doi.org/10.17918/00008977
Abstract
Entity-relationship (ER) modeling has become a recognized aspect of information analysis. Within the paradigm, one of the areas that has not been formally investigated is the ternary relationship. Ternary relationships in ER models continue to be constructs which are misunderstood by educators, difficult to apply for practitioners and problematic in their interpretation to relational schemas. The work analyzes the implicit logic of ternary relationships and how their dynamics are affected by imposing binary constraints between the participating entities. It provides a new construct which allows the recognition and modeling of Semantically Constraining Binary (SCB) relationships. This analysis also allows the development of the Implicit Binary Cardinality (IBC) rule, which addresses the implicit binary relationships within unconstrained ternary relationships. We then investigate the logic of allowing binary constraints within ternary relationships, and the implicit cardinalities required by these impositions. We provide an exhaustive listing of all allowable and disallowed ternary/binary cardinality combinations. We develop two heuristics which govern this process: the Explicit Binary Permission (EBP) rule and the Implicit Binary Override (IBO) rule. As a result of these finding we also provide the Binary Cardinality Propagation (BCP) rule. Having completed the analysis of the dynamics of ternary relationships, we then provide an analysis of ternary decompositions based on binary constraint impositions. We provide templates for lossless and functional dependency preserving decompositions, together with relevant proofs. We provide two heuristics addressing potential decompositions: The Constrained Ternary Decomposition (CTD) rule and the Unconstrained Ternary Decomposition (UTD) rule. The UTD rule has a corollary addressing the ability to model 4th and 5th normal forms. Additionally, we provide three additional sections. One extends the heuristics developed in the ternary relationship analysis to n-ary relationships (>3). The second addresses the difference between the findings in conceptual modeling and the applicability to logical modeling within the relational paradigm. The third looks at examples and applications involving ternary relationships. We then suggest an algorithm detailing the use, logical checking and potential subsequent decomposition of ternary relationships.
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Details
- Title
- An analysis of ternary relationships in entity-relationship modeling
- Creators
- Trevor H. Jones
- Awarding Institution
- Drexel University
- Degree Awarded
- Doctor of Philosophy (Ph.D.)
- Publisher
- Drexel University; Philadelphia, Pennsylvania
- Number of pages
- xi, 167 pages
- Resource Type
- Dissertation
- Language
- English
- Academic Unit
- College of Information Studies (1984-1995); Drexel University
- Other Identifier
- 991021888785304721