What comes to mind here is to automatically generate natural language descriptions of all the circuits in the database and then use standard text searching techniques to search these descriptions. The grammar of these descriptions would probably not be very good but it would not need to be.Lacking is an index that allows a searcher to simply describe something. Search on "skin blister (or bubbles) on bottom of foot," and there are lots of relevant hits. There is no way in electronics to search on something by simply describing it, like "NPN transistor with foreword biased diode to base." Sure, Google will almost always return something, but most of it is not relevant to that question.