10. A method of organising and storing documents in a computer system for subsequent retrieval, the documents having associated metadata terms, the method comprising: providing access to a store of existing metadata in the computer system; analysing the existing metadata to generate statistical data as to co-occurrence of pairs of terms in the metadata of a single document; analysing a fresh document to assign to the fresh document a set of terms and determine for each term of the set a measure of a strength of association of the term with the document; determining for each term of the set a score that is a monotonically increasing function of (a) the strength of association with the document and of (b) a relative frequency of co-ocurrence, in the existing metadata, of the term and another term that occurs in the set; and selecting, as metadata for the fresh document, a subset of the terms in the set having highest scores.
10. A method of organising and storing documents in a computer system for subsequent retrieval, the documents having associated metadata terms, the method comprising: providing access to a store of existing metadata in the computer system; analysing the existing metadata to generate statistical data as to co-occurrence of pairs of terms in the metadata of a single document; analysing a fresh document to assign to the fresh document a set of terms and determine for each term of the set a measure of a strength of association of the term with the document; determining for each term of the set a score that is a monotonically increasing function of (a) the strength of association with the document and of (b) a relative frequency of co-ocurrence, in the existing metadata, of the term and another term that occurs in the set; and selecting, as metadata for the fresh document, a subset of the terms in the set having highest scores. 12. The method according to claim 10 , in which analysis of the metadata generates for each term a set of weights, each weight indicating a number representing how many documents have been assigned both the term in question and a respective other term, divided by a total number of documents to which the term in question has been assigned.