Little work has been completed which addresses the logical composition and use of ternary relationships in entity-relationship modeling. Many modeling notations and most CASE tools do not allow for ternary relationships. Alternative methods and substitutes for ternary relationship structures do not necessarily reflect the original logic, semantics or constraints of a given situation. Furthermore, it has been shown that ternary relationships can be constrained by additional implicit binary constraints which do not occur in the logic of binary relationships. This paper develops an analytical perspective of ternary relationships. We investigate the logical relationships implicit to the ternary structure and then identify potential simplification through decomposition into binary equivalents. These alternative binary equivalents allow retention of the implicit logical structure, and consequently also retain the semantics of the original structure. The analysis investigates equivalency of lossless decompositions, preservation of functional dependencies and finally the ability to preserve update constraints (insertions and deletions). We identify which ternary relationships have true, fully equivalent, binary equivalents and those which do not. We provide an exhaustive analysis of cardinality combinations found in ternary relationships which practitioners can use to guide the way in which they deal with ternary relationships in conceptual modeling.

We review a set of rules identifying which combinations of ternary and binary relationships can be combined simultaneously in semantically related situations. We investigate the effect of these rules on decomposing ternary relationships to simpler, multiple binary relationships. We also discuss the relevance of these decomposition strategies to ER modeling. We show that if at least one 1:1 or 1:M binary constraint can be identified within the construct of the ternary itself, then any ternary relationship can be decomposed to a binary format. From this methodology we construct a heuristic-the Constrained Ternary Decomposition (CTD) rule.>

article Free Access Share on Support for teaching the design and implementation of multimedia/hypermedia systems Authors: Margaret Christensen College of Information Studies, Drexel University, Philadelphia, PA College of Information Studies, Drexel University, Philadelphia, PAView Profile , Michael Giamo Office of Computing Services, Drexel University, Philadelphia, PA Office of Computing Services, Drexel University, Philadelphia, PAView Profile , Trevor Jones College of Information Studies, Drexel University, Philadelphia, PA College of Information Studies, Drexel University, Philadelphia, PAView Profile Authors Info & Claims ACM SIGCSE BulletinVolume 25Issue 1March 1993 pp 242–245https://doi.org/10.1145/169073.169465Online:01 March 1993Publication History 2citation375DownloadsMetricsTotal Citations2Total Downloads375Last 12 Months6Last 6 weeks2 Get Citation AlertsNew Citation Alert added!This alert has been successfully added and will be sent to:You will be notified whenever a record that you have chosen has been cited.To manage your alert preferences, click on the button below.Manage my AlertsNew Citation Alert!Please log in to your account Save to BinderSave to BinderCreate a New BinderNameCancelCreateExport CitationPublisher SiteeReaderPDF