1. A computer-implemented method of controlling and monitoring a drilling operation by determining a set of one or more cases in case-based reasoning (CBR), the method comprising: receiving a data stream comprising information on a monitored situation, wherein the received data stream comprises one or more streams of parameters; using a computer, generating a plurality of parallel data streams, wherein each of the generated plurality of data streams is dependent on the received data stream and each of the generated plurality of data streams is sent to a different one of a plurality of computation units, wherein each computation unit corresponds to a different feature of the same case and each of the generated plurality of data streams comprises only the parameters that are required by the computation unit that the generated data stream is sent to; generating, by each computation unit, a similarity score in dependence on a comparison between information in the generated data stream received by the computation unit and stored information on the feature that the computation unit corresponds to: generating an overall similarity score between the received data stream and the case in dependence on said similarity scores that are generated by the computation units; and controlling the drilling operation based on the overall similarity score.