dW SOA and Web service zone have just published an article on using a Canonical message model in an ESB. Here is the abstract from that article:
Why should you care about a canonical message model (CMM) and the general pattern? Find out in this article, Part 3 of the Exploring the Enterprise Service Bus series. The CMM is a crucial element of the enterprise service bus (ESB). This article explains how to achieve CMM, highlights the characteristics of different approaches, and evaluates the pros and cons of each approach. After reading this article, you'll understand the role and value of CMM for ESB.
Canonical message model in an ESB