*Converting Multiway Relationships to Binary*

On April 06, 2013, In The Entity-Relationship Data Model by Admin

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There are a number of data models, such as ODL (Object Definition Language), which we introduce in "Introduction to ODL", that limit relationships to be binary. Therefore, while the E/R model does not require binary relationships, it is helpful to watch that any relationship connecting more than two entity sets can be converted to a collection of binary, many-one relationships. We can introduce a new entity set

**Example :**The four-way Contracts relationship in "Roles in Relationships" figure, can be replaced by an entity set that we may also call Contracts. As seen in "Subclasses in the E/R Model" figure, it participates in four relationships. If the relationship set for the relationship Contracts has a 4-tuple

(studio1, studio2, star, movie)

Note that we have presumed there are no attributes of entity set Contracts, though the other entity sets in "Subclasses in the E/R Model" figure have unseen attributes. Nevertheless, it is possible to add attributes, such as the date of signing, to entity set Contracts.

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