1. A computer-implemented method of monitoring a situation 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; using a computer, generating a plurality of parallel data streams from the received data stream; using a computer, generating, for each of the parallel data streams, an overall similarity score between the parallel data stream and one of a plurality of cases, wherein each overall similarity score is generated from a comparison between one of the plurality of data streams and a different case; and determining a set of one or more cases in dependence on the generated overall similarity scores.