Chapter 2. The Unified Modeling Language

Who controls the past commands the future.

Who commands the future conquers the past.

attributed to George Orwell

The UML has resurrected modeling as a respectable practice within software development. Indeed, it has moved modeling back into the development spotlight and made it an equal player with coding as an essential skill.

The UML has done this by providing a comprehensive language for modeling. It is every bit as expressive, flexible, and useful as programming languages are for coding and it is at least as complicated in a similar way. More to the point, the UML has made it possible to see object-oriented models as having a legitimate existence outside of the realm of code-production in business modeling, workflow design, and enterprise architecture, for example. These are realms that have been dominated by other modeling approaches until now.

Despite its evolutionary nature, the UML is very different from the modeling tools and languages that preceded it. These differences are what make UML so important to understand (not to mention the reasons why the UML is superseding them all).

This chapter will explore the roots of the UML within the traditions of software development. It will show how the UML is part of those traditions with appropriate history to justify a patterns-based approach for describing good UML modeling practices using patterns based on practical traditions and rules of thumb and allowing for the beneficial inclusion of selected UML-specific idioms.

Chapter 10, "The UML in Context," will explore modeling and the UML (the nature of models and modeling), and Chapter 3, "UML Essentials, Elements, and Artifacts," will provide an introduction to the basic elements and artifacts of the UML and the connections between the UML and patterns. Essentially, it discusses how patterns can contribute to working with the UML in a way that fits the new kind of modeling the UML makes possible.

So, rather than seeing the UML as just another tool, you will be able to see how it can affect the way you work as a software developer how it makes possible a new way to think about modeling.

Just to be clear, the intention of these few chapters is not to provide the ultimate guide to the UML. They will only provide enough context to make the pattern language useful and meaningful. Unlike the built world from which Alexander wove a pattern language, the UML is new fabric. So, we all need a little help with the basics.

Note

I use the terms methodology, process, and method. For this book, the meanings are as follows:

A methodology is a formal packaging of a set of activities, techniques, and end products. It typically has an underlying theoretical basis and an associated modeling language.
A method is a smaller and less-comprehensive version of a methodology. It focuses on the techniques and engineering elements, and it puts less emphasis on the sequencing of specific activities.
A process is like an instance of a methodology with less emphasis on techniques, more emphasis on sequencing of activities, and elements added to support the practical needs of using the methodology (such as management, metrics, and deployment).