This tutorial illustrates the application of design patterns by example. We present in detail a real-world system and describe how it is designed with patterns, with a focus on distribution and concurrency, flexibility, and components. In particular, we will re-play the process of the system's construction step by step, discuss the design problems that occur, present one or more patterns that can help to address these problems, discuss which of the alternative patterns we selected and why, and show how we actually applied the selected patterns. This sequence illustrates how the design of the system slowly evolves towards the final architecture. We will also see that using patterns in practice is influenced by many factors: concrete constraints and requirements set by the application under development, limited or overstated understanding of particular patterns, varying developer skills, and also personal preferences. A major lesson that we can learn from this discussion is that there exists no "right pattern" for addressing a particular design problem, but rather, different patterns apply in different situations.
A reflection on the case study leads us to general guidelines and golden rules for applying patterns in practise, and we discuss how these guidelines and rules aid in building high-quality software with predictable properties. The tutorial concludes with a summary of our experiences from several projects in which we applied patterns: what worked, what could be improved, and what we learned.
Prerequisites: Attendees are expected to have sound knowledge of object technology, and basic knowledge of both UML notation and the pattern concept.
Frank Buschmann is senior principal engineer at Siemens Corporate Technology in Munich, Germany. His interests include Object Technology, Frameworks and Patterns. Frank has been involved in many software development projects. He is leading Siemens' pattern research activities. Frank is co-author of "Pattern-Oriented Software Architecture -- A System of Patterns" and "Pattern-Oriented Software Architecture -- Patterns for Concurrent and Networked Objects".