Sr. Director, Product Research, Epicor Software

Software Architecture

This blog is not associated with my employer.

Sunday, October 02, 2005

Islands of Metadata

Does anyone remember the term “islands of automation”? I’m not sure where it was coined, but it described - in the late '70s - the situation where an enterprise implemented multiple systems with little or no integration. Pretty much every enterprise application has a customer table. Having a CRM system, a logistics system, and, say, a financials system with individual ideas of a customer creates obvious problems.

The “islands of automation” problem was solved in two unsatisfying ways. One way was to install a single big applications suite. The customization costs were big and enterprises were forced to adapt their business to whatever functionality was baked-in the suite. The second way was to buy a set of so-called “best of breed” point solutions. But integrating mission-critical apps can be more expensive than customizing a single app. Neither approach avoided vendor lock-in – whether from an apps vendor or a systems integrator. But I guess that’s sort of the idea, isn’t it.

The metadata-based toolkits under development at Microsoft seem in a similar conundrum. On one side are the individual mechanisms like Indigo, Windows Workflow, DSL, and distributed solutions. Individually, they are interesting toolkits – but they have no awareness of each other. On the other side is Microsoft Business Framework, which uses a single, rather big pile of metadata to describe an application from the database up to the UI. Here we go again: Do I want disconnected best-of-breed metadata, or closed, monolithic metadata.

A Conceptual Leap at PDC 2005

I saw one very promising demonstration at the Microsoft PDC 2005 conference – one that broke a conceptual barrier. Don Box and Dharma Shukla showed Windows Workflow Foundation (WWF) acting as an agent for some Indigo (a post-Whidbey version) services. Indigo-tagged components were dragged into workflow design surface that in turn represented a specific service action. Voila! The service description was inferred from the message “needs” of the application components.

This is significant because loose coupling between application components and the agent layer of the (
canonical) SOA stack means that the agent describes the services. Only the agent knows the complete content of the message. Only the agent knows how to distribute message parts to components.

The other thing I liked was that – for once – the metadata behind WWF wasn’t just source code behind a code generator. Microsoft likes to write tools that spit out reams of partial classes like shot from a Holland & Holland (and about as constructively). Maybe Microsoft feels that OO coupling and static types is how us minions want to develop systems. A more cynical explanation is that nothing sells an idea – at least internally – like good support for IntelliSense. But I digress.

The XOML files used in the WWF/Indigo future-ware demo were processed dynamically (or at least portrayed to be - it was a demo). Generated code may be all the rage, but I only like generated code in one usage pattern: transient assemblies. Here was a great example of an agent that was adept at managing work instances while all the while knowing that the processing plan can change at any moment.

I used to think I was old enough to just let Kool-Aid roll down my back. But seeing the WWF and Indigo teams pick up on this concept definitely brought gave me something to smile about.