Abstract: Apparatus for identifying topics of document data has: a word ranker (171) for ranking words that are present in or representative of the content of the document data; a co-occurrence ranker (172) for ranking co-occurrences of words that are present in or representative of the content of the document data; a phrase ranker (170) for ranking phrases in the document data; a word selector (174) for selecting the highest ranking words; a co-occurrence identifier (176) for identifying which of the highest ranking co-occurrences contain at least one of the highest ranking words; a phrase identifier (177) for identifying the phrases containing at least one word from the identified co-occurrences; a phrase selector (178) for selecting the highest ranking one or ones of the identified phrases as the topic or topics of the document data; and an output device (40) for outputting data relating to the selected topics.

Abstract: Apparatus for identifying topics of document data has:

Abstract: A computer implemented abductive reasoner checks for contradictions in the reasoning operations during processing and determines subsequent processing dependent upon the results of the checking. Constraints on variables may be imposed to permit proofs to be pursued which otherwise would involve contradictions. Different types of abductive reasoning step may be assigned different costs and proofs or future processing steps selected dependent upon the costing. Alternatively or in addition, reasoning operations and the resulting proofs, if any, may be grouped according to the types of reasoning steps involved and provision may be included for pursuing operations involving less costly reasoning steps in preference or prior to operations which may be more costly. Where successive goals are to be proved, the proof of each successive goal may be performed by reference to hypotheses established in proofs of previous goals.