Web Services References

Iwrote about notification-based Web service systems one year ago (“Web Services Notification,” Mar./Apr. 2004, pp. 86–90). To properly address the topic, I devoted a significant portion to Web service references, which are, conceptually, like network handles that refer to Web services. Service references are particularly important for notification systems, which usually require subscribers to register service references to receive notification messages. Given that they appear in one form or another in almost every distributed system, service references are nothing new. Nevertheless, no standardized service reference exists for Web services. Among other things, the WS-Addressing specification,1 which entered the W3C (www.w3.org) standardization process in October 2004, specifies a construct called an endpoint reference (EPR), which is much like a service reference. I’m a member of the WS-Addressing working group (WG), and we’ve made good progress toward turning the specification into a standard — the process might even be complete by late 2005. In this column, I discuss a few issues that I raised in the WG regarding the features needed to turn the EPR into a flexible and useful Web service reference.