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copied!<p>An example where abstraction has failed:</p> <p>In this case, a piece of software was needed to communicate to many different third party data processors. The communication was done through various messaging protocols; the transport method/protocol is not important in this case. Just assume everyone communicated through messaging.</p> <p>The idea was to abstract the features of each of these third parties into a single, unified message format. It seemed relatively straightforward because each of the third parties performed a similar service. The problem was that some third parties used different terms to explain similar features. It was also found that some third parties had additional features that other third parties did not have.</p> <p>The designers of the abstraction did not see through the difference of third party terms nor did they think it was reasonable to limit the scope of the unified features to only support the common features of the third parties. Instead, a single, monolithic message schema was developed to support any and all features of the third parties considered at the time. In what was probably considered a future-proofing move, they added a means of also passing an infinite number of name/value pairs along with the monolithic message in case there were future data elements that the monolithic message could not handle.</p> <p>Early on, it became clear that changing the monolithic message was going to be difficult due to so many people using it in mission critical systems. The use of the name/value pairs increased. Each name that could be used was documented inside a large spreadsheet, and developers were required to consult the spreadsheet to avoid duplication of name value function. The list got so large, however, that it was found that there were frequently collisions in purposes of name values.</p> <p>The majority of the monolithic message's fields now have no purpose and are kept mainly for backwards compatibility. There are name values that can be used to replace fields in the monolithic message. The majority of the interfacing is now done through the name/value pairs. In cases where the client is intending to communicate with more than one third party, each client needs to reconcile the name values available for each third party. It would be almost simpler to interface directly to the third party themselves.</p> <p>I believe this illustrates that, from a consumer of the monolithic message perspective, that it is important that developers of the consuming code <em>not</em> know what is happening under the covers. If the designers had considered that the consumers of the monolithic message <em>should not</em> have to understand the abstraction in great detail, the monolithic message and it's associated name/value pairs might never have happened. Documenting the abstraction with assertions regarding input and expected output would make life so much simpler.</p> <p>As for colleges not teaching C and Lisp....they are cheating the students. You get a better understanding of what is going on with the machine and OS with C. You get a bit of a different perspective on processing data and approaching problems with Lisp. I have used some of the ideas I learned using Lisp in programs written in C, C++, .Net, and Java. Learning Java after knowing even just C is not very difficult. The OO part is really not programming language specific, so perhaps using Java for that is acceptable.</p>

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