Though I don’t work with most of these areas, the things mentioned in the title always puzzle me, mainly by producing such questions in my mind as - Are they all the same or are they different? How are they going to affect our (I.T’s I mean) future etc. Here is what I understood so far on each of these things and how they are related, please correct if I’m wrong(and you are right)
Grid computing – A technique in which multiple small computing environments are connected and exposed to outside as a single unit of big processing power, data storage etc.
Utility computing – I think this is more of a business term that refers to somebody offering computing abilities as an external service to those in need of it, where they don’t have to invest in buying own computers on their own. SaaS I would say is an offshoot of this
Cloud computing – Ah! Trouble! Let me escape by saying this – it’s a model where grid capabilities are used in the back-end to deliver computing services to customers?
SOA – I know to some extend what that is, so I would say it’s about the way the computing services are exposed by the environments that provide those as cloud/utility services, so that consumers can have a common mechanism to reach to the servicing systems.
Though there are too much noise in this space currently, I think it will all settle eventually and we will have well tuned computing-on-demand environments available to use. Now the million dollar question is ‘by when?’. Since we are in recession and cannot afford any million dollar stuff, I don’t have an answer.