No abstract

In this paper we introduce the Biased Cost Pathfinding (BCP) algorithm as a simple yet effective meta-algorithm that can be fused with any single-agent search method in order to make it usable in multi-agent environments. In particular, we focus on pathfinding problems common in real-time strategy games where units can have different functions and mission priorities. We evaluate BCP paired with the A* algorithm in several game-like scenarios. Performance improvement of up to 90% is demonstrated with respect to several metrics.

Natural language text corpora are often available as sets of syntactically parsed trees. A wide range of expressive tree queries are possible over such parsed trees that open a new avenue in searching over natural language text. They not only allow for querying roles and relationships within sentences, but also improve search effectiveness compared to flat keyword queries. One major drawback of current systems supporting querying over parsed text is the performance of evaluating queries over large data. In this paper we propose a novel indexing scheme over unique subtrees as index keys. We also propose a novel root-split coding scheme that stores subtree structural information only partially, thus reducing index size and improving querying performance. Our extensive set of experiments show that rootsplit coding reduces the index size of any interval coding which stores individual node numbers by a factor of 50% to 80%, depending on the sizes of subtrees indexed. Moreover, We show that our index using root-split coding, outperforms previous approaches by at least an order of magnitude in terms of the response time of queries.

Many existing indexes on text work at the document granularity and are not effective in answering the class of queries where the desired answer is only a term or a phrase. In this paper, we study some of the index structures that are capable of answering the class of queries referred to here as wild card queries and perform an analysis of their performance. Our experimental results on a large class of queries from different sources (including query logs and parse trees) and with various datasets reveal some of the performance barriers of these indexes. We then present Word Permuterm Index (WPI) which is an adaptation of the permuterm index for natural language text applications and show that this index supports a wide range of wild card queries, is quick to construct and is highly scalable. Our experimental results comparing WPI to alternative methods on a wide range of wild card queries show a few orders of magnitude performance improvements for WPI while the memory usage is kept the same for all compared systems.

There is a huge body of domain-specific knowledge embedded in free-text repositories such as engineering documents, instruction manuals, medical references and legal files.Extracting ontological relationships (e.g., ISA and HASA) from this kind of I also want to thank the NSERC BIN funding for supporting me on this ontology extraction research project, it gives a great opportunity to learn more about my research area and sharpen my technical skills.Finally, I would like thank my mom, who always supports me from China, which is 9,000 km away from here, and gets me through all good times and bad times.viii