About five years ago I worked for a company where we implemented a web-based enterprise SaaS solution for supply chain. In those days we didn't know it was SaaS, and we called ourselves an ASP (Application Service Provider). However, if it smells like an apple, feels like an apple and tastes like an apple...guess what, it's probably an apple :). I could go into a similar story about AJAX, but I wont.
Recently there was a question on the forums around WCSF and SaaS (Software As A Service). The question was on how WCSF fits in with the SaaS model. One of the cornerstones of SaaS is multi-tenancy. In its essence, a multi-tenant web application is one that is driven by metadata in order to allow it to look and behave differently depending on the customer who is accessing it.
In a multi-tenant solution, the data for multiple customers all lives in the same place and is tagged with additional metadata that defines which customer the data belongs to. For example in the simplest form (only for illustration) imagine each row in the database was tagged with a CustomerID. The system then automatically embeds the appropriate CustomerID in all queries to ensure that ONLY the appropriate data is retrieved. There are actually several variations on this where you can have separate databases / servers for each customer, however this is not a long-term scaleable solution.
Back to the WCSF question. One of the beauties of WCSF is our guidance "does what we do best" and then leaves the rest for you to implement as you will. In the case of SaaS, we don't give specific guidance within the factory on building SaaS sites. However, there are several capabilities within WCSF that play very well in a multi-tenant solution, and we definitely don't block you from implementing a SaaS solution.
Of course the real heavy lifting of implementing the multi-tenant infrastructure is up to you, but when you do, WCSF can work nicely with it.
For more info on SaaS and multi-tenant architecture, check here. Also check out Eugenio Pace's blog. Finally, if guidance on SaaS is something you'd like to see us deliver, please tell us with your vote.