While programming my bootstrap English dialog system, I needed a spreading activation library for the purpose of enriching the discourse context with conceptually related terms. For example given that there is a human-habitable room that both speakers know of, then it is reasonable to assume that "on the table" has meaning "on the piece of furniture" in the room rather than the meaning "subject to negotiation". This assumption can be deductively concluded by an inference engine given the room as a fact, and rules concluding the typical objects that are found in rooms. But performing theorem proving during utterance comprehension is not cognitively plausible, and would take too long for real-time performance. Suppose that offline deductive inference provides justifications (e.g. proof traces) to support learned links between rooms and tables, then spreading activation is a well known algorithm for searching semantic graphs for relevant linked nodes.
A literature search provided much useful information regarding spreading activation, also known as marker passing, especially about natural language disambiguation, which is my topic of interest. Because there are no general purpose spreading activation Java libraries available, I wrote one and just released it on the Texai SourceForge project site. The download includes Javadoc, an overview document, source code, all required jars (Java libraries), unit tests and examples, and GraphViz illustrations of sample graphs. Performance is acceptable: 20,000 nodes can be activated in 24 ms with one thread on my 2.8 GHz CPU. Furthermore the code is multi-threaded and it gets about a 30% speed increase by using two CPU cores. Even if you are not interested in spreading activation, the Java code is a clear example of using a CyclicBarrier and CountdownLatch to control worker threads with a driver. A practice I recommend to you all is to improve Wikipedia articles on AI topics of interest. Therefore I elaborated the existing article on spreading activation to include the algorithm and its variations. Cheers. -Steve Stephen L. Reed Artificial Intelligence Researcher http://texai.org/blog http://texai.org 3008 Oak Crest Ave. Austin, Texas, USA 78704 512.791.7860 ____________________________________________________________________________________ Be a better friend, newshound, and know-it-all with Yahoo! Mobile. Try it now. http://mobile.yahoo.com/;_ylt=Ahu06i62sR8HDtDypao8Wcj9tAcJ ------------------------------------------- agi Archives: http://www.listbox.com/member/archive/303/=now RSS Feed: http://www.listbox.com/member/archive/rss/303/ Modify Your Subscription: http://www.listbox.com/member/?member_id=8660244&id_secret=98558129-0bdb63 Powered by Listbox: http://www.listbox.com
