Controlling and coordinating tool interactions in a CASE environment require an approach to tool integration that is sufficiently flexible and adaptable to suit different user needs, as well as simple and efficient. These conditions will ensure that new tools can easily be integrated and that their productivity is not significantly impaired. As discussed in the previous chapter, one traditional approach toward tool integration has been based on data sharing, often through a common database in which all tools deposit their data. While this approach can provide a high level of control and coordination between tools, it also imposes a significant overhead on the tools, both because of poor performance of existing database mechanisms when used in this way, and because of the necessary agreement required between the tools to define a common syntax and semantics for their data (e.g., a common data schema). Another approach to integration has been called the control integration approach. This approach is based on viewing a CASE environment as a collection of services provided by different tools. Actions carried out by a tool are announced to other tools via control signals. The tools receiving such signals can decide if the other tool’s actions require that they take any actions themselves. For example, when an editing tool announces that changes have been made to a source file, a build tool may receive this information and initiate a new system build. In addition, one tool may directly request that another tool perform an action by sending it a control signal. For example, the build tool may request that the source file be compiled by a particular compiler. Hence, the primary means of coordination between tools is through the sending and receiving of control signals. In the rest of this chapter, we examine the notion of control integration in a CASE environment, review a number of existing systems, and analyze those systems to identify their differences and to reveal interesting future directions for this work. The reviewed systems do not represent an exhaustive examination of systems implementing a control integration approach.
Homeostatis and Control-integration as basic principles in the physiology of man