67. The method of claim 66 wherein retrieving at least one negation term comprises retrieving at least one prefix negation term and at least one suffix negation term.
66. A ranking method comprising: executing a document ranking application on a processor to rank documents retrieved from a data source in response to a search request, the document ranking application comprising a term frequency module, a negation module, a ranking module, and a user interface module; querying the data source at the term frequency module to identify a plurality of documents that each comprises a key term, the key term matching a search term in the search request; determining a corresponding term frequency value at the term frequency module for the key term in each of the plurality of documents, the term frequency value comprising a total number of occurrences of the key term in a particular document; retrieving negation terms and negation rules from a memory using the negation module, the negation terms comprising prefix negation terms and suffix negation terms, the negation rules comprising a prefix negation rule comprising that a prefix negation term appear before the key term in a same sentence as the key term within a selected proximity and a suffix negation rule comprising that a suffix negation term appear after the key term in the same sentence as the key term within the selected proximity, the selected proximity comprising a selected number of words; comparing the negation terms at the negation module to other terms in each document within the selected proximity of each occurrence of the key term and according to the negation rules; excluding a particular occurrence of the key term in each document at the negation module if at least one negation term matches another term according to the negation rules within the selected proximity of the particular occurrence of the key term; determining a corresponding term weight value for the key term in each document at the negation module based on each occurrence of the key term that has not been excluded; determining a corresponding relevancy ranking value for each document at the ranking module based on the corresponding term frequency value and corresponding term weight value, the relevancy ranking value comprising a document relevance (DR) value comprising a ratio comprising the term weight (TW) value in a numerator of the ratio and the term frequency (TF) value in a denominator of the ratio; and generating a list of document data for display at the user interface module, the list identifying the plurality of documents in order based on the corresponding relevancy ranking value of each document.