Systems, devices, and methods are disclosed in relation to a system for natural language based message categorization designed to identify text from a particular topic from a potentially inexhaustible set of potential topics. In one of many possible implementations, a vector space model is first used to translate text into a vector representation. This vector is used to determine if the text can be recreated by swapping words and phrases from a training corpus of documents. This is done by determining if the vector is within the conical span of the vector representations of the text in the training corpus of documents. Span composition is evaluated by a two vector boolean comparison, enabling great computational complexity and short-circuiting enabling fast real-time topic determination.