Gianpaolo Carraro (Microsoft) has produced an interesting diagram laying out the benefits of Software-as-a-Service (SaaS) to various actors.
This makes clear that different actors have different motivations to get involved in SaaS - and for that matter SOA. Each actor may have several parallel motivations, with different perceived urgency levels. In his blog, Gianpaolo discusses the typical short-term and longer-term interests for each of the types of enterprise he identifies. This is useful material, and helps us to see different adoption paths for SOA and SaaS within different organizations.
But there is a common pattern here as well. The potential benefits of SaaS indicated here are mostly architectural ones (Gianpaolo is an architect himself, after all) - changing the configuration of the stack, changing your own position within the stack - delivering not just economies of scale but also economies of scope and economies of governance.
So I'm not just interested in the content of Gianpaolo's picture, but the underlying process. This is the kind of business case that depends more on PowerPoint than on Excel. The trouble with this, of course, is that PowerPoint lacks rigour. Ideally, we need to develop better ways of producing architectural models that support reasoning about business benefits.
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