Dependence management in component-based distributed systems

Recent component-architecture developments—such as Enterprise JavaBeans, ActiveX Controls, and the CORBA Component Model—support the construction of sophisticated systems by assembling a collection of off-theshelf software components with the help of visual tools or programmatic interfaces. However, very little support exists for managing the dependencies between components. Different programmers create components, often working in different groups with different methodologies. It is hard to create robust and efficient systems if they do not understand the dynamic dependencies between components. Thus, it is very common to find cases, in both legacy and componentbased systems, in which a module fails to accomplish its goal because the system does not properly resolve an unspecified dependency. Sometimes, other modules do not properly detect the graceful failure of one module, which leads to a total system failure. Dependence problems To further illustrate the importance of understanding and managing component dependencies, consider a similar problem in a different context. Because administrators must continuously update and modify current systems, dependency conflicts may arise. For example, UNIX and Windows NT system administrators must monitor security announcements daily and be prepared to update their operating system kernels with the appropriate security patches. In addition, users demand new versions of applications such as Web browsers, text editors, software development tools, and so forth. Often, building and installing a new software package requires updates to a series of other tools as well. Like system administrators, workstation and personal computer users are also burdened with system or account maintenance. In environments such as Microsoft Windows, wizard interfaces partially automate some application installations by directing users through the installation The authors present