Research in the Life Sciences depends on the integration of large, distributed and heterogeneous data sources and web services. The discovery of which of these resources are the most appropriate to solve a given task is a complex research question, since there is a large amount of plausible candidates and there is little, mostly unstructured, metadata to be able to decide among them. We contribute a semi-automatic approach, based on semantic techniques, to assist researchers in the discovery of the most appropriate web services to fulfill a set of given requirements.