Information extraction and database techniques: A user-oriented approach to querying the Web

We propose a novel approach to querying the Web with a system named AKIRA (Agentive Knowledge-based Information Retrieval Architecture) which combines advanced technologies from Information Retrieval and Extraction together with Database techniques. The former enable the system to access the explicit as well as the implicit structure of Web documents and organize them into a hierarchy of concepts and meta-concepts; the latter provide tools for data-manipulation. We propose a user-oriented approach: given the user's query, AKIRA extracts a target structure (structure expressed in the query) and uses standard retrieval techniques to access potentially relevant documents. The content of these documents is processed using extraction techniques (along with a flexible agentive structure) to filter for relevance and to extract from them implicit or explicit structure matching the target structure. The information garnered is used to populate a smart-cache (an object-oriented database) whose schema is inferred from the target structure. This smart-cache, whose schema is thus defined a posteriori, is populated and queried with an expression of PIQL, our query language. AKIRA integrates these complementary techniques to provide maximum flexibility to the user and offer transparent access to the content of Web documents.