Chapter 5: An Overview of Object Role Modeling

Overview

It goes without saying that, in general, application designers and architects spend a lot of time thinking about the proper design of their systems and applications. A well-designed application will pay for itself many times over with benefits such as maintainability, scalability, and extensibility for years to come. The same benefits of good software design also hold true for the database components of two-tier and three-tier applications, which probably include the majority of enterprise applications. In the long term, a good design will save money, and a bad design will cost money—it’s that simple.

For the last 25 years, entity relationship (ER) modeling has been the leading standard methodology for conceptual database design. ER was, and still is, a popular notation for graphically defining the structure of a database.

Object Role Modeling (ORM) is a relatively new technique for modeling database design. It is considered a successor to ER in that it fixes a number of the apparent deficiencies in the ER method. For instance, although ER models can be quite useful for documenting the design for a system, they are less useful for creating and evolving a design through a series of steps. Also, ER models do not support some of the advanced constraints that are available in the ORM method. In this chapter, we will learn more about ORM and proceed step-by-step through the process of designing a database.

Exam Watch

Although the 70-300 exam may contain only a few ORM-related questions, the official Microsoft study guide devotes a full section to it.