The Service-oriented Vision Understanding Service- Oriented Software Service-oriented Software

evolution. While they address some aspects of the problem, however, understanding the software still poses some difficulty. This shift toward service orientation compels us to consider its implications for software understanding, which is potentially the primary cost in software engineering. 2 Using an example of on-the-fly software services construction, we discuss the problems software engineers still face when working with service-oriented software. We also introduce some new issues that they must consider, including how to address service provision difficulties and failures. Software evolution still poses a significant problem for many organizations despite new development methods that promise to enable flexibility and simplify systems' evolution as business needs change. Among the largest costs is the time software engineers spend trying to understand existing software, either to fix bugs or add functionality. We use the term software understanding to mean the application of techniques and processes that facilitate understanding of the software. We need this understanding to ensure the software evolves through the application of various maintenance activities. The SaaS framework, advanced as a solution to the evolution issue, 3 automatically discovers fine-grained software services, negotiates to acquire them, and composes, binds, executes, and unbinds them. This process potentially occurs for every execution of the software, and would M any hail service-oriented software as the next revolution in software development. Web services' capabilities are constantly expanding from simple message passing toward the construction of full-fledged applications such as those envisaged by the UK's Pennine Group in their Software as a Service (SaaS) framework. 1 These new, service-oriented approaches appear to many to solve the significant issue of software inflexibility that arises during maintenance and Service-oriented software lets organizations create new software applications dynamically to meet rapidly changing business needs. As its construction becomes automated, however, software understanding will become more difficult.