COTS Integration: Plug and Pray?

135 Management F or most software applications, the use of commercial off-the-shelf products has become an economic necessity. Gone are the days when upsized industry and government information technology organizations had the luxury of trying to develop—and, at greater expense, maintain—their own database, network, and user-interface management infrastructure. Viable COTS products are climbing up the protocol stack, from infrastructure into applications solutions in such areas as office and management support, electronic commerce , finance, logistics, manufacturing, law, and medicine. For small and large commercial companies, time-to-market pressures also exert a strong pressure toward COTS-based solutions. However, most organizations have also found that COTS gains are accompanied by frustrating COTS pains. Table 1 summarizes a great deal of experience on the relative advantages and disadvantages of COTS solutions. 1 One of the best COTS integration gain-and-pain case studies 2 summarizes the experiences of David Garlan's group at CMU. Garlan's group tried to integrate four COTS products into the Aesop software architecting environment—the OBST object management system, the Mach RPC Interface Generator, the SoftBench tool integration framework, and the InterViews user interface manager—only to find a number of architectural mis-matches among the products' underlying assumptions. For example, three of the four products are event based, but each has different event semantics, and each assumes it is the sole owner of the event queue. Resolving such model clashes escalated the original two-person, six-month project into a five-person, two-year project: a factor of four increase in schedule and a factor of five increase in effort. Such experiences, and the more general technical and business issues shown in Table 1, indicate that COTS integration differs significantly from traditional software development and requires significantly different approaches to its management. At the USC Center for Software Engineering COTS Integration Affiliates' Workshop, we identified four key COTS integration issues: functional-ity and performance, interoperability, product evolution, and vendor behavior. You have no control over a COTS product's functionality or performance. If you modify the source code, it's not really COTS—and its future becomes your responsibility. Even as black boxes, big COTS products have formidable complexity; Windows 95, for example, has roughly 25,000 entry points. Let the buyer beware COTS-based projects cannot make blanket assumptions about system requirements or embrace traditional process models. One mistake developers can make is to use the waterfall model on a COTS integration project. With the waterfall model, you specify requirements and these determine the …