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Aug 07The Mythical Business Layer
by in Alex's Soapbox on 2007-09-25If you’ve developed software for long enough, you’ve most certainly heard of a “business logic layer.” It’s supposed to be the layer (or “tier”) containing an application’s business logic and is sandwiched between a “persistence layer” and a “presentation layer.” Some call that the “standard three tiers of an application.” But what it really is, however, is a bad design that leads to bad software. Or at the very least, dangerously poor semantics. In lieu of your standard WTF article, allow me to explain why.
First and foremost, we need to define the term “business logic.” Unlike so many other entries in the IT lexicon, “business logic” has no standard meaning. We’re left with what you think it is, what your colleague wants it to be, and what some article you read says it is. So, for the purpose of this article (and hopefully beyond), here is my definitive definition.