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So far, four tentative classes have been created as shown in this diagram. The same attributes (Name, Date of birth, and Hire date) are repeated in each class. Additionally, two classes have additional attributes (Workstudy has Entry Date and Professor has Tenure Date).

Each of these tentative classes will become what is know as leaf classes in the class hierarchy. Leaf classes are at the end, or bottom, of the class hierarchy much like leaves are at the end of tree branches. The hierarchy now must be expanded to intermediate or non-leaf classes. Potential intermediate classes can be identified by either inspecting the tentative classes for shared attributes or using multi-type view as defined in the relational schema. In this example, we will use multi-type views to define new classes.

Tentative Classes

Next: Multi-type views. Also see the related content below.

Related Articles

More on the general topic: Using Type Codes to Construct Classes

Related Fact Book

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The Savvy Manager's Guide

Douglas K Barry is also the author of a book that explains Web Services, service-oriented architecture, and Cloud Computing in an easy-to-understand, non-technical manner.

Web Services, Service-Oriented Architectures, and Cloud Computing: The Savvy Manager's Guide

Web Services, Service-Oriented Architectures, and Cloud Computing: The Savvy Manager's Guide (Second Edition)

by with David Dick

This is a guide for the savvy manager who wants to capitalize on the wave of change that is occurring with Web Services, service-oriented architecture, and—more recently—Cloud Computing. The changes wrought by these technologies will require both a basic grasp of the technologies and an effective way to deal with how these changes will affect the people who build and use the systems in our organizations. This book covers both issues. Managers at all levels of all organizations must be aware of both the changes that we are now seeing and ways to deal with issues created by those changes.