13. A computer system for automatically determining document relevance, the computer system comprising computer hardware configured to perform operations comprising: representing a plurality of terms as a tree data structure comprising internal nodes and leaf nodes interconnected by respective node connections; assigning to each of the leaf nodes of the tree data structure a respective one of the terms; assigning to at least one of the leaf nodes a respective location specifying a designated location for the term assigned to the leaf node to appear within a document; assigning a respective operator to each of the internal nodes of the tree data structure; assigning a respective operator to each of the node connections in the tree data structure; and calculating a respective relevance value for at least one document as a function of occurrence in the at least one document of the terms respectively assigned to the leaf nodes of the tree data structure, the operators assigned to parent internal nodes of the corresponding leaf nodes, and the weights assigned to the associated node connections and, for each of the leaf nodes assigned a respective location, occurrence of the term assigned to the leaf node at the location in the at least one document specified by the respective location assigned to the leaf node.
13. A computer system for automatically determining document relevance, the computer system comprising computer hardware configured to perform operations comprising: representing a plurality of terms as a tree data structure comprising internal nodes and leaf nodes interconnected by respective node connections; assigning to each of the leaf nodes of the tree data structure a respective one of the terms; assigning to at least one of the leaf nodes a respective location specifying a designated location for the term assigned to the leaf node to appear within a document; assigning a respective operator to each of the internal nodes of the tree data structure; assigning a respective operator to each of the node connections in the tree data structure; and calculating a respective relevance value for at least one document as a function of occurrence in the at least one document of the terms respectively assigned to the leaf nodes of the tree data structure, the operators assigned to parent internal nodes of the corresponding leaf nodes, and the weights assigned to the associated node connections and, for each of the leaf nodes assigned a respective location, occurrence of the term assigned to the leaf node at the location in the at least one document specified by the respective location assigned to the leaf node. 15. The computer system of claim 13 wherein: each assigned operator is one from a group consisting of: maximum, minimum and add.