The previous section of this book broadly covered the basics of the VAST Web services implementation. As we begin to cover this framework more in depth, we need to introduce the concept of the Web services platform. As illustrated in Figure 1, the Web services platform is built upon several existing VAST Platform features, in particular, Server Smalltalk (SST) and XML. Server Smalltalk was chosen in order to leverage its server and transport framework. XML was chosen for its flexible and robust parsing engine.

The design of the framework revolves around three tenets: