13. The system of claim 12 , the first level document being related to the base document as one or more of, an attached document, an attaching document, a referenced document, and a referencing document.
13. The system of claim 12 , the first level document being related to the base document as one or more of, an attached document, an attaching document, a referenced document, and a referencing document. 14. The system of claim 13 , where the relevance logic is to determine the relevance of the virtual document to the query using a term frequency value, an inverse document frequency value, and a nearness value.