Service Oriented Architecture is an umbrella term very similar to that other umbrella term, “web services”. SOA refers more to how these web services interact, however, in a system. Below is a diagram I’ve knocked up which shows in a very crude fashion the difference between traditional models and SOA.
I hope this explains it a little… frankly, some of the diagrams out there that are supposed to explain SOA simply look like someone’s eaten a technical dictionary, felt ill and thrown it all up.
I’ve explained SaaS and DaaS in some detail in this blog. We’ll talk about PaaS later. Expect this diagram to pop up again when I do.
You can reproduce this simple diagram wherever you like so long as you give a little attribution by linking back to this blog.
Edit: here’s a more detailed description of Service-Oriented Architecture.

October 6, 2008 at 4:37 pm
Hi, there!
May I know further about SOA from you? I’m interesting to knowing this subject beacause i’m making a thesis that involved the concept and methodology of this SOA… Thank you with your help… I’m awaiting your reply
October 6, 2008 at 4:41 pm
Hi Wihemdra. You can ask any questions you like and I’ll try and answer them here… I work with several highly technical people who should also be able you furnish you with detailed info.
October 7, 2008 at 1:43 am
I really curios the differences between SOA and SODA(Service Oriented Database Architecture).. May I know from you the detail of them? If possible explain the methodology of SODA. Thank you…
October 7, 2008 at 10:28 am
It is my understanding that SODA isn’t really used that much any more (certainly to mean Service Oriented Database Architecture) …
It seems to be pretty much a rather outmoded way of saying “DaaS” but seen in the context of SOA… looks like it was coined by Microsoft but didn’t really catch on: http://www.microsoft.com/sql/techinfo/whitepapers/why-soda.mspx
As such, it looks at the way data is held in the cloud and at the user end.
There is a pretty long and mind-bogglingly boring run-down here: http://www.microsoft.com/technet/prodtechnol/sql/2005/sqlsoda.mspx
SaaS and DaaS are outlined here:
http://mrwebservice.wordpress.com/2008/09/26/saas-and-daas/
Thansk for another pointless acronym, Microsoft!