13. A computer system comprising; a storage subsystem; and at least one processor coupled to the storage subsystem, the at least one processor being configured to: extract and store in the storage subsystem a set of candidate phrases from a corpus of documents, wherein each candidate phrase corresponds to a group of two or more words that occur consecutively in at least one of the documents in the corpus; compute a statistical metric for each of the candidate phrases based on occurrence count data indicating a number of occurrences of the candidate phrase in documents of the corpus and a number of occurrences of the words making up the candidate phrase, wherein the statistical metric indicates a likelihood of the words within the candidate phrase occurring consecutively chance; select phrases from the set of candidate phrases as meaningful phrases, the selection being based on the statistical metric; compute a phrase weight for each of the meaningful phrases, the phrase weight being based on a number of documents in the corpus that contain a corresponding meaningful phrase; and form clusters of the documents using the phrase weights.
13. A computer system comprising; a storage subsystem; and at least one processor coupled to the storage subsystem, the at least one processor being configured to: extract and store in the storage subsystem a set of candidate phrases from a corpus of documents, wherein each candidate phrase corresponds to a group of two or more words that occur consecutively in at least one of the documents in the corpus; compute a statistical metric for each of the candidate phrases based on occurrence count data indicating a number of occurrences of the candidate phrase in documents of the corpus and a number of occurrences of the words making up the candidate phrase, wherein the statistical metric indicates a likelihood of the words within the candidate phrase occurring consecutively chance; select phrases from the set of candidate phrases as meaningful phrases, the selection being based on the statistical metric; compute a phrase weight for each of the meaningful phrases, the phrase weight being based on a number of documents in the corpus that contain a corresponding meaningful phrase; and form clusters of the documents using the phrase weights. 17. The computing system of claim 13 , wherein the at least one processor is configured to further construct a document vector for each of the documents, the document vector including a first plurality of components corresponding to words and a second plurality of components corresponding to at least some of the meaningful phrases, the second plurality of components being based on the phrase weights for the at least some meaningful phrases, and wherein forming the clusters comprises comparing the document vectors.