Paper report 2


D. B. Lenat. CYC: A Large-Scale Investment in Knowledge Infrastructure. Communication of the ACM, vol 38, pages 32-38, November, 1995.


The paper introduce an AI project called CYC , which is ambitious to gather a comprehensive ontology of everyday common sense knowledge. CYC is a rule based system which contains millions of facts and rules describing common sense. The goal of CYC is to perform human-liked reasoning in AI applications such as enabling computer to understand an article and can also makes a conclusion about the article it read. Briefly, there are many powerful features and applications of CYC that seems have feasible usage for the semantic web in the future.


In order to make computer become more intelligent and can do simple inference as human, it is necessary to create an knowledge based system that enable computer to absorb knowledge and using inference engine to do inference. CYC attempt to gather common sense knowledge from human expert and formatted the knowledge it has gathered using CycL language, which is a representation of every assertion stored in CYC KB. CYC also has nature language processing feature so that it can parse articles and transform them into CycL representation to do inference. For example, after CYC have gone through some texts, it will de-contextualize the texts to see what the context the texts lie on is. Since different contexts will have different assertion and inference rule (we can see someone’s heart in a surgery, but we can not see someone’s heart in a classroom. Surgery and classroom are different contexts in this example). So the inference mechanism CYC use is to explicitly identify the different contexts and using the appropriate rule and assertions to do reasoning. Moreover, all assertions in CYC KB are assumed to be true by default because it’s hard to really construct a standard to check whether a common sense assertion is true or false. In my opinion, although it seems that CYC is so powerful, but there are many drawbacks like that CYC is lack of any meaningful benchmark or comparison for the efficiency of the inference engine, CYC’s inference is not complete , gathering knowledge from experts’ entered data is not efficient , etc. I think knowledge can be retrieved from the WWW using AI techniques in the attempts to reduce human efforts and increase system efficiency. The question I am pondering about is that common sense will change according to different cultures and nations, and change with time pass, how CYC deal with this kind of problems seems crucial in real world applications.


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