SOAaaSaaS

Serendipitously to John's recent post on "Consumption is not Free," Dave Linthicum just put out a great note on SOA as a SaaS (or "SOAaaSaaS") that nicely covers requirements of the Publish side of delivering reusable services. Merits further thought... http://weblog.infoworld.com/realworldsoa/archives/2007/03/soa_as_a_saaswh.html Where is all of this going? SOA and SaaS are mutually very compatible and may overlap, but they are not mutually inclusive. SaaS is really more of a business model for reaching end customers - delivering a business over the Internet, generally through a browser instead of requiring the end user to install a client or other software on their side. The method of creating a SaaS can be done as a SOA, but in most cases, it is developed as a vertically integrated platform that the SaaS provider can control, even if some parts of the SaaS are exposed as Services. On the other hand, delivering a reusable Service in SOA fashion, even for profit, is not necessarily a SaaS. That Service might need interpretation and certification as a "good citizen" before being offered to the end customer. The real question, and maybe this is just a point of distinction for the pundits and analysts, is: Does a SaaS need to be a complete business offering - or core to the business model, or is any Service offered for profit technically a SaaS? For my part, I'd say the terms belong to different software disciplines, one architectural, the other marketing related:

1. SOA is a business strategy for aligning IT assets as Services in a loosely-coupled way to support business processes with more flexibility and agility.
2. SaaS is a business model for offering or selling software (or a business service, with a small "s" and not a technology Service) to end customers without the installation or client requirements. Most SaaS offerings are actually vertically integrated web implementations of software under a single brand's authority domain, which isn't always in the SOA spirit.

Of course, the discussion does have value, especially if we look back at it in a year or so. We expect someday to offer certified Services that obey expected behaviors in a "for profit" way, yet to do SOA these services need to be cooperative at the same time. But enough for now, we could make distinctions with SOA, SaaS, Web 2.0, etc. all day long, without even getting into the underlying technologies or the overarching Governance strategy.