Web Services
-thoughts on service orientated architectures


Thursday, December 19, 2002

Loosely Coupled - it is all about when  

The debate of loosely coupled has for the moment ignored when in the software lifecycle an implementation is loosely coupled. This is an important distinction that needs to be considered. It is not to say that one approach is wrong or right but that it is understood and is specified appropriately. So what are the milestones when an architecture can be described as loosely coupled and what does it mean. This concept is tightly associated with late binding and or lazy evaluation.
A rough timeline can be consider as follows:


  • Vision/Powerpoint: This is when marketing and sales latch onto the concept and use it as a sales tool

  • Design Time/Compile Time: The design is modular and if necessary a module can be replaced with another module providing the interfaces and functionality of the module is tightly specified

  • Run Time: This is the most important form of loose coupling, when a system is in production its behavior and purpose can be changed without rebuilding the entire system


If the system in question is a single application the timeline is less significant, when the system is a distributed system with no central control there is a significant impact. The closer the design is to achieving run time loose coupling the more successful it will be. Successful web service projects outside the firewall must strive for very late binding and high degrees of loose coupling as change is inevitable and success will be measured by how well change is handled.

Comments []

posted by John McDowall | 10:48 AM

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