3 - The Unified Modeling Language (UML)

Abstract

This chapter is an overview of the syntax and semantics of the UML class and activity diagram constructs. The Unified Modeling Language (UML) is a graphical language for communicating design specifications for software. The object-oriented software development community created UML to meet the special needs of describing object-oriented software design. UML has grown into a standard for the design of digital systems in general. There are a number of different types of UML diagrams serving various purposes. The class and activity diagram types are particularly useful for discussing database design issues. UML class diagrams capture the structural aspects found in database schemas. UML activity diagrams facilitate discussion on the dynamic processes involved in database design. UML class diagrams and entity-relationship (ER) models are similar in both form and semantics. The original creators of UML point out the influence of ER models on the origins of class diagrams. The influence of UML has in turn affected the database community. Class diagrams appear frequently in the database literature to describe database schemas. A class is a descriptor for a set of objects that share some attributes and/ or operations.