Enveloping Sophisticated Tools into Computer-aided Software Engineering Environments

We present a CASE-tool integration strategy based on enveloping pre-existing tools without source access or assuming an API or any other special capabilities on the part of the tool. This Black Box enveloping (or wrapping) idea has been around for a long time, but was previously restricted to relatively simple tools such as compilers. We describe the design and implementation of a new Black Box enveloping facility intended for sophisticated tools | often with graphi-cal user interfaces | with particular concern for the emerging class of groupware applications. 1 Introduction CASE environments usually support dialogues with commercial-oo-the-shelf (COTS) tools. There are three main categories of integration methods, with respect to their approach to adapting the external applications to the environment: White Box, where a custom tool is implemented as part of a particular environment or a pre-existing tool's source code is modiied to match the environment framework's interface. Custom tools may be prohibitively expensive to develop. Changes to pre-existing tools can often be implemented in a straightforward, repetitive manner , but nevertheless the source code must be available | perhaps an insurmountable diiculty when integrating COTS tools from independent vendors. The White Box approach is followed by several commercial message buses, most based ultimately on Field 19]. PCTE 22] and similar framework standards probably require more effort in tool adaptation, but enable a higher scale of integration. Grey Box, where the source code is not modiied but the tool provides its own extension language or application programming interface (API) to interact with the environment; relatively few tools provide such convenience. In principle, dynamic linking coupled with replacement of standard libraries might work, but it seems unlikely that arbitrary COTS tools would happen to t a frame-work's communication protocols. For instance, a framework may expect tools to ask permission before accessing objects, so that task prerequisites and concurrency control can be considered, and/or to notify a broadcast message server when updates have been completed for propagation to other tools 18]. Black Box, when only binary executables are available and there is no extension language or API. In this case, the environment must provide a protocol whereby envelopes 9] extract objects from the environment's internal representation, present these objects to their \wrapped" tools in the appropriate format, and provide the reverse mapping for updated data and tool return values. Envelopes can also be used as mediators in the Grey and White Box …