1. A machine-implemented method for identifying patterns in text using structures defining types of patterns which are to be identified, wherein a structure comprises one or more definition items, the method comprising: assigning a fixed weighting to each structure and each definition item in each structure, each fixed weighting being an integer multiple of the same integer; searching the text for a pattern to be identified on the basis of a particular structure, a pattern being provisionally identified if it matches the definition given by said particular structure; in a provisionally identified pattern, determining definition items making up said particular structure that have been identified in the provisionally identified pattern; combining the fixed weightings of the determined definition items and the fixed weighting of the particular structure to a single quantity; assessing whether the single quantity fulfils a given condition; and depending on the result of said assessment, rejecting or confirming the provisionally identified pattern.