I recently read “Data on the Outside vs. Data on the Inside” by Pat Helland and I have to say that it is one of the best articles I’ve read so far on service orientation.

The article discusses data in a service oriented world. It distinguishes data that exists inside the service (private service implementation data) from data that exists outside of the service boundaries (data transferred between services) and talks in depth about the characteristics of each type of data.

BTW You can also see Pat Helland talking about SOA in this TSS.net interview.