Saturday, March 28, 2009

DCI, or restoring order to OO

Object orientation (OO) is often contrasted with structured programming (SP). OO has many advantages when it comes to managing complexity, but it clearly lacks in exposing clairly what the code is actually achieving. SP on the other hand has many defeciencies when it comes to separation of concerns and maintainability, but at least it is normally possible to follow the execution sequence in the code.

In my OO training courses, I frequently warn the attendees, saying that OO may solve the problem of complexity and changeability, but requires another level of competence to maintain clarity and overall understandability. A lack of this competence may produce a spaghetti code that is an order of magnitude worse that the traditional, structured spaghetti code. Please be warned!

Enters Professor Trygve Reenskaug, the principal inventor of the MVC paradigm, with a new DCI paradigm, supported by Jim Coplien. As I understand it, DCI is complementing OO and MVC, supplying the overall interaction scheme, showing how the individual objects, based on their roles, collaborate to deliver business value: It supplies a role based expression of the communication logic, like in sequence or communication diagrams.

I have to look closer into the material, for instance how DCI expresses the communication scheme better than e.g. communication digrams, but it does look interesting.

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