Out of the tar pit

A really good paper. Definitely worth a read. See here: http://shaffner.us/cs/papers/tarpit.pdf. Ben Moseley and Peter Marks.

Complexity is the single major difficulty in the successful development of large-scale software systems. Following Brooks we distinguish accidental from essential difficulty, but disagree with his premise that most complexity remaining in contemporary systems is essential. We identify common causes of complexity and discuss general approaches which can be taken to eliminate them where they are accidental in nature. To make things more concrete we then give an outline for a potential complexity-minimizing approach based on functional programming and Codd’s relational model of data.

There is nothing in the paper that should have surprised a relational audience. Indeed they might have sat back and quietly nodded or applauded at the appropriate places. Mind you, it’s pretty basic stuff and lacks higher order operations.

There was quite a bit to puzzle or even offend a TTM advocate, in the comments about a suitable language. The type system, the structure and even the scope and purpose of the language would be hard to reconcile with D. Some of these are mentioned on p63.

I saw a Feeder as a way to obtain data from a non-relational source, which will necessarily result in the execution of an INSERT/UPDATE/DELETE operation. An Observer would be a way for external logic to execute as a consequence of a change in relational state (the issue of trigger vs polling is unimportant). The result could be as simple as updating a screen display or something more complex like sending an email or synchronising with another system. These are very MVC-like concepts.

My main disappointment with the paper is that the (hoped for) final section is missing or severely truncated. The expose of problems is excellent as far as it goes, but the fragments of concrete solution presented are unsatisfying. This paper got some attention here: http://lambda-the-ultimate.org/node/1446. Moseley released some source code, but does not seem to have worked on this much since about 2006. See: https://groups.google.com/forum/?fromgroups#!topic/frp-discuss/BNmBgtqRUFY.

In a nutshell, he captures what I would like to do, but doesn’t help all that much with solving the problem of how to do it.

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