Here's an illustrative diagram of VPxM's reliable messaging.

Web Services' Limitations in Reliability

Web services' underlying protocol, SOAP, can be viewed as either a XML document messenger or a XML version of RPC (Remote Procedure Calls). In either case, there is no mechanism guaranteeing message delivery. SOAP does not provide asynchronous messaging which has the capability of delivering messages reliably via managed queues.

Instead of HTTP, Web services can be implemented using SOAP over an asynchronous messaging protocol such as JMS (Java Message Service) to improve reliability. These implementations, however, are usually confined to specific operable environment. For instance, implementating SOAP over JMS is practical only on the J2EE platform within a protected intranet environment.

VPxM's Reliable Messaging Framework

VPxM provides a reliable messaging framework for Web services. Reliability is ensured by having the VPxM distributed messaging agents seamlessly transform ordinary Web services into asynchronous messaging component services with embedded queuing mechanism.

In essence, these messaging agents:

• deliver messages in fail-safe asynchronous mode


• are equipped with persistence engines using embedded databases


• come with built-in robust queue management systems