16. A computer system for extracting topic words from electronic documents based on at least one seed word comprising: a. a programmable computer processor; b. a memory readable by the processor; and c. software stored in the memory for execution by the processor, the software comprising: i. a keyword identification module for identifying keywords in each document that are indicative of the topic of the document; ii. an evaluation module for evaluating the relevance of each of the documents to the at least one seed word; iii. a key topic document identification module for identifying at least one key topic document that is relevant to the at least one seed word; iv. a selection module for selecting a subset of the documents, referred to as topic documents, by an iterative process starting with the at least one key topic document and then selecting other documents if their keywords are sufficiently similar to the keywords contained in the previously selected topic documents; and v. an extraction module for extracting a set of topic words from the topic documents.
16. A computer system for extracting topic words from electronic documents based on at least one seed word comprising: a. a programmable computer processor; b. a memory readable by the processor; and c. software stored in the memory for execution by the processor, the software comprising: i. a keyword identification module for identifying keywords in each document that are indicative of the topic of the document; ii. an evaluation module for evaluating the relevance of each of the documents to the at least one seed word; iii. a key topic document identification module for identifying at least one key topic document that is relevant to the at least one seed word; iv. a selection module for selecting a subset of the documents, referred to as topic documents, by an iterative process starting with the at least one key topic document and then selecting other documents if their keywords are sufficiently similar to the keywords contained in the previously selected topic documents; and v. an extraction module for extracting a set of topic words from the topic documents. 17. The system of claim 16 wherein each document comprises an index, and the evaluation module produces a sorted list of document indices that include the at least one seed word based on relevance to the at least one seed word, and identifies at least one key topic document index that is highly relevant to at least one seed word.