“Quality of Service” is a general term that refers to a number of topics in different fields within computing. For web services, it means simply the set of supporting infrastructure that enhances the reliability, security, performance, and overall ability of your system to do its job in accordance with its contract. In web services, these ideas are supported by a set of specifications that complement each other and rely on each other to support message reliability and delivery guarantees, metadata, transactions, and security.
These concepts are likely familiar to you through EJB. Indeed, this list is very similar to the enhancements that a container provides around an EJB to make it operate as a full-blown component.
While there are more than 100 WS-* specifications, they are not all used, and some are more central to our work than others. This chapter will examine a small set of specifications that address quality-of-service issues, including those for transactions, reliability, and policy metadata. Given the breadth and scope of these specifications, and the wide array of vendors that incorporate them into their products, it would be impossible to cover everything about these specifications in one chapter, or even one book. Here I attempt to hit some of the primary use cases you’ll encounter.
The web service features that we examine in this chapter are reliability, transactions, and metadata. These are expressed ...