I have just got my hands on a copy of the SOA Sourcebook, produced by the SOA Work Group of The Open Group and launched at the Open Group Architecture Practitioner Conference. (See my review of the Open Group Boston Grid.) I also spoke with Chris Harding, Forum Director for SOA and Semantic Interoperability.
Most of the ideas in the SOA Sourcebook have been circulating around the SOA world for some time, and there is (not surprisingly) a lot of overlap (with more or less variation) with material the CBDI Forum has published from 2003 onwards.
Some of this material has also found its way into TOGAF 9, but the SOA working group is not tightly coupled with the Architecture Forum (responsible for TOGAF).
The SOA Sourcebook defines SOA as an architectural style, although it also defines it as a construction technique. As an architectural style, service orientation can apply to the business architecture as well as to the software (application) architecture and the technology (infrastructure) architecture, and you can have any of these without the other two if you want; but as the SOA Sourcebook acknowledges "many people believe that the greatest benefits of SOA are obtained when it is applied to the business architecture".
However, the SOA Sourcebook focuses on the IT component of enterprise architecture - in other words, service orientation as applied to the software (application) architecture - and this is where the view of SOA as a construction technique would also make sense.
The motto of the Open Group is "Boundaryless Information Flow". The SOA Sourcebook shows how SOA can achieve permeable boundaries, but of course that's not the same thing as lack of boundaries. For a deeper analysis of boundaries, you are going to have to look at Chapter 4 of my book on the Component-Based Business. But there are clearly construction issues as well as strategic requirements when joining loosely coupled lumps of enterprise as well as loosely coupled lumps of software.
Inclusion in a long term IT strategy, created by Enterprise Architecture, is the only good justification for large-scale SOA. From an SOA perspective, this might be interpreted as saying that the de facto purpose of EA is to justify SOA. Clearly there is a common interest between EA practitioners and SOA practitioners, which The Open Group will doubtless continue to develop.