Document filtering via directed acyclic graphs

Abstract

A method and mechanism for for filtering incoming documents against user queries. A plurality of user queries including terms connected by logical operators is received. Terms and sub-expressions are combined into distinct sub-expressions and embedded into a directed acyclic graph (DAG) having a plurality of nodes. Each node in the DAG includes pointers to any successor nodes thereof, the terms in the queries are embedded as source nodes in the graph, and the operators embedded as internal nodes. When a document is received, the document is evaluated against the nodes in the DAG by comparing the relevant terms in the document with the source nodes in the DAG representative thereof. For each term that matches a source node, the internal successor node of the matched source node is evaluated based on the logical operator represented by the successor node and truth information of the predecessor nodes thereto, thereby determining a truth value of the internal successor node. Information is returned indicative of which of the successor nodes were evaluated as true. From that information, the queries which matched the document and the users corresponding thereto can be determined.