An example
A client requires a three-dimensional FFT. A request is made to a broker or matchmaker for a FFT service based on the keywords and possibly parameter lists.
The broker or matchmaker uses the keywords to retrieve its catalog of services and returns with the candidate remote services.
Literally dozens of different algorithms for FFT computations with different assumptions, dimensions, accuracy, input-output format and so on.
The client must validate the actual functionality of these remote services before the client commits to use it.