Day 2 of the SPARK workshop was an attempt to develop frameworks that encapsulated the architectural response to the challenges identified in Day 1. The photoset on Flickr includes some dreadful pictures of me (here with Michael Platt of Microsoft and here with Nick Gall of Gartner), but it also includes copies of most of the flip charts.
The group I was in (which included Glen Harper, Dion Hinchcliffe and Michael Putz) tried to summarize some of the issues around the business stack.
Note the differential rate of change, as well as the gradients of innovation and trust. Note also the questions of horizontal and vertical coupling, which the group discussed but did not resolve.
This is a framework not a fixed solution. For example, in some cases the trust/compliance regime may be stricter (or at least different) at the top of the stack (think healthcare and HIPPA), but in most cases the greatest perceived risks will be associated with the major business assets (legacy) at the bottom of the stack. And (as Anne Thomas Manes reminded us) enterprise innovation isn't always going to be focused exclusively on customer-facing stuff, but may be focused on supply chain or product development or elsewhere.
Different technologies will be appropriate for different levels of the stack - for example we might expect to see SOAP and WS-* at the bottom of the stack (high trust, high engineering) and REST at the top of the stack (low trust, agile).
Of course, stratified architectures and stack diagrams are not new, but they have traditionally been produced from a purely technological perspective (client/service, 3-tier, n-tier computing, and so on). To my mind, the new architectural challenge here is to manage the stratification of layers in a way that responds in an agile and effective way to (the complexity of) the business/user challenges. (Hence Asymmetric Design.)
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