Articles by Jack van Hoof

SOA, BPM and DFD and the Art of Designing Systems

Thu, 24 Apr 2008 14:30:00 EDT

Back in the 70s everybody knew that programming was not about writing code, but about the art of designing algoritms. Edsger (Edgar) Dijkstra used the term 'elegance' for correctly designed algoritms and everybody knew exactly what he meant. Every programmer and designer knew about Structured Analysis, Structured Design and Structured Programming as rationally described (so not intuitive) approaches to develop systems. Part of these approaches is the Data Flow Diagram technique (DFD). And exactly this technique is extremely useful in the context of today's BPM.

SOA Viewpoint: How To Mediate Semantics in an EDA

Thu, 13 Mar 2008 11:15:00 EDT

Systems that pass data to each other share commonly understood semantics. Explicit data semantics is the key to success in an EDA (and any other messaging system). In striving for loose coupling, data semantics is the ultimate level; when systems are decoupled at the semantic level - e.g. they don't share semantics - the coupling becomes useless, because in this case the systems will not be able to communicate at a logical level. Shared semantics is a prerequisite in connecting distinct systems, no matter whether it concerns EDA, SOA or any other form of EAI (Enterprise Application Integration). It should be obvious to anyone that analysis of data semantics will always be the first activity of any integration project.

How EDA Extends SOA and Why It Is Important

Wed, 12 Mar 2008 14:30:00 EDT

Everything is moving toward on-demand business where service providers react to impulses - events - from the environment. To excel in a competitive market a high level of autonomy is required, including the freedom to select the appropriate supporting IT-systems. The world is preparing for network oriented business structures with independent autonomous service providers and service consumers.

SOA Viewpoint: Layers are Encapsulations and Tiers Are Barriers

Wed, 12 Mar 2008 07:15:00 EDT

I came across an interesting article of Arnon Rotem-Gal-OZ about the (mis)use of the layered architecture style. I found it an interesting article, although I have an essentially different view. I think the model of layers and tiers is a services model. As it is a services model to me, I view the model of layers and tiers as a logical model. The services are physically delivered by components; ultimately one service by one component. So the counterpart of the logical services model is a physical component model, that needs not necessarily map one-to-one to the logical model.