Object Role Modeling

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 arc 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.

Object Role Modeling (ORM) is a process for developing the conceptual design for a database. ORM uses natural language to describe the conceptual elements of a system, such as objects and roles. In fact, Object Role Modeling provides a step-by-step process for creating a conceptual database design known as the Conceptual Schema Design Procedure (CSDP).Within the context of overall application design, database design might be one of the most important things to do properly. A well thought-out database design will influence application design in a positive way, while a poorly thought-out database design will have the opposite effect. Those of you who have had to design applications that run on preexisting poor designs know how hard it can be.

In short, Object Role Modeling is a well-developed and casy-to-understand method for modeling data at a conceptual level. Object Role Modeling consists of both the process for creating this model, called Conceptual Schema Design Procedure (CSDP), and the language associated with the model, called Formal Object-Role Modeling Language (FORML). Object Role Modeling has been designed to be understandable, capable, reliable, stable, and executable. We can elaborate on how it satisfies these design objectives as follows:

• Understandable   Business rules are written in plain language.
• Capable   The graphical model supports many different advanced business rules.
• Reliable   Business rules are validated using real sample data.
• Stable   It is easy Object Role Modeling make changes to the model.
• Executable   The ORM conceptual data model can be mapped directly to a fully normalized relational database schema.

Questionnaire:

• What is Object Role Modeling? Explain.