The "sketchboard": a dynamic interpretative memory and its use for spoken language understanding

Blackboards allow various knowledge sources to be triggered in an opportunistic way, but does not allow higher modules to feedback information to lower level modules. The solution presented here remedies this shortcoming, since our Sketchboard implements reactive feedback loops. Within the Sketchboard, modules are considered from two points of view: either they build a result (a sketch, possibly rough and vague) or they give back a response to the modules from which they received their input data. This response signals the degree of confidence the module has towards its own result. These relations are generalized across all the modules that interact when solving a problem. As higher and higher level modules are triggered, the initial sketch become more and more precise, taking into account the higher modules knowledge. Conceived for natural language processing, the Sketchboard is also useful for spoken language understanding as shown by a detailed example.