focus US Government Work Not Protected by US Copyright Published by the IEEE Computer Society IEEE SOFTWARE 59 use models even more rarely for later integra- tion efforts, when the systems have been re- peatedly patched or have become brittle and the models themselves are often inaccessible, if even applicable. However, can models be more than tools discarded along the way? Might they provide the enterprise with enduring value? Engineers can use these models to automate some sys- tems integration steps that occur as systems evolve. If models can enable automated inte- gration methods, the overall integration costs will decrease and modeling efforts’ enduring value will return because models will become key to a wider segment of the system’s life cycle. Our approach to model-driven integration uses a system’s existing models to characterize how the system’s resources might be used to ful- fill requirements for new interactions. Links- across-views capture the design intent behind legacy systems. They are combined with re- quirements for new interactions to produce a joint action model. Developers can use the JAM in downstream, automated integration. Views of business activity In modeling the interactions and communi- cations that let subsystems work together, at least two distinct levels of abstraction are im- portant: conceptual (or business) views and engineering views. Model-Driven Integration Using Existing Models A s we engineers develop systems, we build models. These models might include business policy guidelines, database schemata, or- ganization charts, class diagrams, and so on. The models span di- verse viewpoints and levels of formality. We seldom revisit these models as the enterprise evolves. Often, the mod- elers themselves have disappeared, and any knowledge that wasn’t captured in the specialized models is inaccessible, forgotten, or written off. Engineers model-driven development Peter Denno, Michelle Potts Steves, Don Libes, and Edward J. Barkmeyer, US National Institute of Standards and Technology While developing software systems, and during the enterprise’s subsequent evolution, developers define models. These models can help automate some systems integration tasks. The joint action model describes a new business transaction that motivates systems integration.