Rule Engine Horror Stories

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Updated Oct 20 2008:

There were some interesting responses to an article at the blog site about rule engine performance.

A comment by Greg Barton outlines a disaster story about the inappropriate use of a rule engine to implement transaction processing for a large telecom application.

... The thing is, by design, they did not want to process the data in a non-monotonic manner and also had few joins between working memory objects. In other words, data was processed (mainly validated) once, then never touched again by this particular system.

Using a rules based system was unnecessary in that case. The system, by initializing the rete network, was effectively preparing for nonmonotonic work, but it was never being done. CPU cycles were being burned in preparation for work that, by design, would never happen: the very definition of waste ...

How many times have I encountered this sort of story, maybe a dozen multi-million dollar meltdowns. If the knowledge domain is fairly static, use old fashion tables and code.

See the article Un-Rule Engines for Business Rules.