From ODL Designs to Object-Relational Designs

From ODL Designs to Object-Relational Designs

In "From ODL Designs to Relational Designs" we learned how to convert designs in ODL into schemas of the relational model. Difficulties arose primarily because of the richer modeling constructs of ODL: nonatomic attribute types, relationships and methods. Some, but not all, of these difficulties are alleviated when we translate an ODL design into an object-relational design. Depending on the specific object-relational model used (we shall look at the concrete SQL-99 model in "Object-Orientation in Query Languages"), we may be able to convert most of the nonatomic types of ODL directly into a corresponding object-relational type; structs, sets, bags, lists, and arrays all fall into this category.

If a type in an ODL design is not available in our object-relational model, we can fall back on the techniques from "Nonatomic Attributes in Classes" through "Representing Other Type Constructors". The representation of relationships in an object-relational model is basically the same as in the relational model (see "Representing ODL Relationships"), though we may prefer to use references in place of keys. Finally, though we were not able to translate ODL designs with methods into the pure relational model, most object-relational models include methods, so this restriction can be lifted.

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