I like the "discoverer, informer" part. That is what we mean by a server of which you can ask a question.
An index can be that which points,- like an index finger, or the index into an array. This emphasises that the index need not contain the data (wheras a databse usually does)
What we really mean by index in the W3 world is any algorithm taking human input and generating a view as a function of that input. There need not be a database, for example in the square-root server]Tim