Take a look at Starmind (starmind.ai). It's a tool that uses AI to create a 'neural network' of association between people and concepts, based on digital content to which it has access (e.g. intranet files). It attempts to standardize vocabulary differences and spelling errors. Users can then use it to find out who (in the internal network) is likely to know about X, or what concepts has person Y worked on? So whilst it may not tell you who is a true expert (which is subjective anyway), it's a good starting point. It also avoids the need to maintain profiles. There is a cost unfortunately.
Happy to connect separately.
Jonathan Gordon-Till / UK