The SOA thing as I would explain to my mother

Take SAP SCM tool as an example. To be able to do transportation planning the addresses of customers, vendors and plants need to be defined in geographical coordinates, so that it becomes possible to define and optimize the distance between places. This task of finding the latitude and longitude from the address data is called geocoding.

With SCM comes a plug-in software that one can install to do the geocoding. Of course this is not a very powerful tool, it comes with a limited database of addresses and just for some countries. This is the traditional architecture, the software has some plug-in that solves a particular need.

But with some little work one can plug the SCM to use the geocoding web service provided by Yahoo or Google. That way one can get very good geocoding without the burden of having to buy, install and update a large geocoding address database. This is the SOA architecture. The software uses a stand-alone webservice internal or external to the company.