TABLE OF CONTENTS Before discussing ORM s conceptual schema design procedure, let s review the fundamental design principles that underlie the ORM language itself. Some of these ideas were mentioned before, but I ll generalize the discussion here so that you can apply the principles to evaluate modeling languages in general. As you work your way through the book, you should consider how these principles are realized in the various languages discussed.
A modeling method comprises both a language and a procedure to guide modelers in using the language to construct models. This procedure is often called the modeling process. A language has associated syntax (marks), semantics (meaning), and pragmatics (use). Written languages may be graphical (diagrams) and/or textual. The terms abstract syntax and concrete syntax are sometimes used to distinguish underlying concepts (e.g., object type) from their representation (e.g., named ellipse).
Conceptual modeling portrays the application domain at a high level, using terms and concepts familiar to the application users, ignoring logical- and physical-level aspects (e.g., the underlying database or programming structures used for implementation) and external-level aspects (e.g., the screen forms used for data entry). The following criteria drawn from various sources (van Griethuysen 1982; ter Hofstede 1993; Bloesch and Halpin 1996) provide a basis for evaluating conceptual modeling languages:
Expressibility
Clarity
Simplicity and orthogonality
Semantic stability
Semantic relevance
Validation mechanisms
Abstraction mechanisms
Formal foundation
The expressibility of a language is a measure of what it can be used to say. The...
