Designed originally for document delivery, the Web is now being widely used as a platform for electronic commerce application software. The ad hoc enhancements that have made Web application software possible (for example, CGI and Java Script) have created an application support infrastructure where application software upgrades and maintenance are very complex. Yet the Web is the preferred platform for applications that have continuous ongoing development needs. In this chapter, we describe a model, an architecture, and an associated Web Application Support Environment (WASE) that both hides the low-level complexity of the existing Web infrastructure and, at the same time, empowers enterprise Web application programmers in their objective of writing modular and easily maintainable software applications for electronic commerce. WASE is not a compiler and does not completely abstract away the unique features of Web infrastructure. It is being constructed using XML documents in its API, to allow the function and configurability of applications to be defined in a Web-like fashion.