Friday, September 18, 2009


This paper may have had some significance back in its day, but it seemed like nothing more than Common Sense 101. It didn’t add anything to what I consider the standard pattern of layering your architecture to group certain concerns and layers of abstraction together and decouple different layers.

Refactoring to this pattern will become exponentially more difficult as the project progresses. Trying to refactor a big ball of mud would be extremely difficult because of all the coupling.

I’m not quite sure of the difference between this pattern and pipes and filters other than pipes and filters seemed to be talking about having all the code at the same low-level of abstraction with quick & small filters, while this paper was talking about larger modules at different levels of abstraction. The OSI example seemed to wrap the data from each layer, while the streaming multimedia examples of pipes and filters operated on the same data over and over.

My professional experience as far as planning the architecture has matched the authors’ recommendations. It is extremely difficult to work from the bottom up and predict what low-level services you will need to provide the higher layers without knowing the services that the higher layers will provide. The yo-yo way of working from top to bottom back to top & repeating has served me well.

I have also found that having layer J depend on any layers other than J-1, whether they be above J or below J-1, is a slippery slope and degrades most of the benefits of this pattern.

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