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The Road Ahead for UML

Ivar Jacobson is founder and CTO of Ivar Jacobson International and co-developer of UML. Steve Cook is a software architect at Microsoft and represents Microsoft at the OMG.

More than 12 years have passed since the Unified Modeling Language (UML), became a standard. During these years opinions of UML have varied between delight and distaste. In this article, we discuss the deficiencies of the current UML specification and propose how to make it agile, leaner, smarter, and more flexible -- in short, how to prepare it for the future so that users can be confident that their investments in UML today will increase in value going forward.

At the beginning of the '90s there were 26 published methods on object-orientation, most with its own notation with its own set of icons. It was in this environment that UML was born. Although Grady Booch, Jim Rumbaugh, and Ivar Jacobson initiated the design of what became UML, many other contributors (including Steve Cook) quickly joined the effort and the Object Management Group (OMG) launched the result. UML quickly made most other methods -- along with their own notations, obsolete -- UML eventually became the standard we had hoped for, and toolbuilders and practitioners rapidly adopted the new approach.

Since UML first had outstanding success, we all knew that the pendulum would swing in the opposite direction some day -- and we were right. After a few years the setback arrived, but admittably for good reasons. For instance, at the outset there weren't many good UML tools. Some were very advanced, but hard to use. That disappointed many users and hindered the wide adoption of UML. The language received criticism from the academic world; for example David Parnas nicknamed it the "Undefined Modeling Language". The criticism was exaggerated, but not unfounded. Likewise, the original leaders of the agile movement were negative to modeling. They said "no modeling -- just code". Many people were skeptical about the tools, so they worked more with UML sketches on the whiteboard than formally with the tools themselves.

However, the pendulum is now swinging back. The tools have become better. Criticism from academics has mostly stopped. Agility has come to big companies and modeling is agile if done sensibly (and not as a "silver bullet"). Microsoft, for instance, has implemented UML in Visual Studio 2010, alongside domain-specific languages. Other important standards such as SysML are implemented as extensions to UML.

Thus it seems that today the world looks upon UML with a more balanced view. UML is not the panacea that it was sometimes sold as 10 years ago. Nor is it as bad as some academics, agilistas, and competitors have claimed. It is a practical tool to raise the level of abstraction of software from code to system level. Many organizations claim benefits from their use of UML, ranging from improved communication among developers to productivity gains using code generation from UML models.

UML is a good language to describe software systems at a higher level than code. Properly used UML can improve productivity and quality. After several years of consolidation, the OMG (the owner of the UML) is taking the initiative to improve it, having issued a Request for Information (RIF) on the Future Development of UML in 2009 under the leadership of Steve Cook.

The results of this RFI showed that users and vendors want UML to be leaner, more expressive, easier to learn, easier to integrate with other modeling and programming languages, and more relevant to today’s technologies. For example, some users want to use UML to drive the interactive behavior of a mobile application. Others want to use UML diagrams to automatically visualize the structure and dependencies within a massive distributed service-oriented application. Some would like models to be deeply integrated with modern programming languages without any semantic conflicts. Increasingly, users would like to use UML to model applications deployed in the Cloud. To address these needs, the OMG and UML vendors are working together towards making UML smarter and more agile.

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