Showing papers by "David Martin published in 1998"

Using Information Extraction to Improve Document Retrieval

Abstract: : The authors describe an approach to applying a particular kind of Natural Language Processing (NLP) system to the TREC routing task in Information Retrieval (IR). Rather than attempting to use NLP techniques in indexing documents in a corpus, they adapted an information extraction (IE) system to act as a post-filter on the output of an IR system. The IE system was configured to score each of the top 2000 documents as determined by an IR system and on the basis of that score to rerank those 2000 documents. One aim was to improve precision on routing tasks. Another was to make it easier to write IE grammars for multiple topics.

On the complexity of the containment problem for conjunctive queries with built-in predicates

Abstract: When the inputs are conjunctive queries with #, 5, or < as built-in predicates, the query containment problem ‘is Qr 5 Qz?,, is I$-complete and, thus, highly intractable. In this paper, we investigate the impact of syntactic and structural conditions on the computational complexity of tho query containment problem for safe conjunctive queries with discquation # as a built-in predicate. In the case of Np~r~‘, conjunctive queries (no built-in predicates), it is known that the boundary between polynomial-time solvability and NP-completeness is crossed, when the number of occurrcnccs of any database predicate in Qr increases from two to three, We show here that, as regards safe conjunctivc qucrics with disequations, the same syntactic condition dolincatcs the boundary between membership in coNP and II?$completencss, Moreover, it is also known that the “pure” conjunctive query containment problem is solvable in polynomial time, if the hypergraph associated with the database predicates of Qz is acyclic. In contrast, we show that the vory samo structural condition does not lower the computational complexity of the containment problem for safe conjunctivc queries with disequations, that is, the problem remnins II~completc. We also analyze the computational complexity of the quary equivalence problem for conjunctive queries with disequations, when one of the two queries is fixed. We show that this problem can be DP-complete, where DP is the class of nil decision problems that are the conjunction of a problem in NP and a problem in coNP. It follows that, as regards conjunctive queries with disequations, the complexity of the query cquivalcncc problem may be higher than the complexity of the query containment problem, when one of the two qucrics is fixed.

Multimodal user interfaces in the Open Agent Architecture

Abstract: The design and development of the Open Agent Architecture (OAA)3 system has focused on providing access to agent-based applications through an intelligent, cooperative, distributed, and multimodal agent-based user interface. Only the primary user interface agents need run on the local computer, thereby simplifying the task of using a range of applications from a variety of platforms, especially low-powered computers. An important consideration in the design of the OAA was to facilitate the reuse of agents in new and unanticipated applications, and to support rapid prototyping. The utility of the agents and tools developed has been demonstrated by their use as infrastructure in unrelated projects.

Information extraction research and applications: current progress and future directions

Abstract: Analysts face a daunting task: they must accurately analyze, categorize, and assimilate a large body of information from a variety of sources and for a variety of domains of interest. The complexity of the task necessitates a variety of information access and extraction tools which technology up to this point has not been able to provide. SRI's TIPSTER Phase III project has focused on two major obstacles to the development of such tools: inadequate degrees of accuracy and portability. We begin by providing an overview of SRI's information extraction (IE) system, FASTUS, and then describe our efforts in these two areas in turn. We then conclude with some thoughts concerning future directions.