Loosely Coupled ZapFlash

, Jun 6, 2004

Another nice paper from ZapThink: How to Think Loosely Coupled. Certainly not exhaustive, and also a bit too high-level for my taste (and I’m not sure I agree with the one-WSDL-many-components issue), but the ZapThink folks clearly are a lot more knowledgeable than most of the other “analysts” that talk about SOA.

On June 7, 2004 3:27 PM, Hartmut Wilms said:

Hi Stefan!

In my opinion the “many-to-many” relationship between WSDL and “components” makes perfect sense.

I like to think of Web Services as a UI (Use case Interface) for server components that implement the business logic. Maybe the ZapThink Folks had a similiar “Web Service Facade” thing in mind, when speaking of this “many-to-many” relationship. In this scheme WSDL is the common vocabulary for publishing these UIs.

To sum up, one interface maybe implemented by several components and one component maybe accessed via several interfaces, which provide a client specific approach to the business logic requested: WSDL-Component-Many-To-Many relationship.

Am I missing something?

On June 7, 2004 4:07 PM, Stefan Tilkov said:

Hartmut, actually I agree - I just don’t think that this has much to do with loose coupling. Loose coupling, IMO, is achieved by decoupling consumers and providers by means of indirection, asynchronous messaging, document-based communication as opposed to common type systems, and many other aspects.

On June 7, 2004 4:45 PM, Hartmut Wilms said:

I like to distinguish between logical and physical coupling. ” … indirection, asynchronous messaging, document-based communication ” are physical aspects, which allow for loose coupling of systems.

Separating client access to a (service) component by providing indirection via multiple facades is IMO a “logical” loose coupling.

So loose coupling is achieved by physical means as well as logical means … I’m aware that the logical part is by no means as “buzzy” as the physical ;-).