A Partial Taxonomy of Knowledge about Actions

An incomplete taxonomy is proposed for the knowledge of actions a computer must have if it is to understand stories about people performing these actions. The classification is along two dimensions , Force-why a person should follow the rule, and Form-what the rule looks like. For the most part it seems that any force type may combine with any form type in producing a rule. One example, how to use an umbrella, is examined in detail although facts about many human activities, from playing bridge to washing one's hair, are used as examples. I Introduction It is commonly accepted that a computer which answers questions about a natural language text must have roughly a human reader's knowledge of the subject matter. Restricting ourselves to simple stories (1 ike children's stories) the knowledge needed is that "common sense" knowledge which all members of a particular culture share. Since, by all indications even this knowledge is quite extensive, it will have to be well organized and classified before a computer will be able to make much use of it. In this paper I will be concerned with classifying the kinds of facts we have about actions. Some typical facts of the sort I will be concerned with are: (Fl) In giving a present the giver should give something the receiver would like to get. (F2) When painting some object it is a good idea to put paper on the floor under the object so as not to get paint on the floor. Some facts which would not be included in this study, as they are intuitively not about actions, are: (F3) The Earth has one moon. (F4) Few people like modern music. Furthermore, this study will be restricted to facts like (F1)-(F2) which tell us something about how to perform an action, as opposed to facts like: <F5) Many people break their legs while skiing. (F6) At playing chess, nobody is much better than Bobby Fisher. Intuitively it seems to me that the "how to do it" type facts form a natural subclass of knowledge , so that by restricting the study to them I will not be hopelessly distorting the results. Naturally it would be preferable to have some firm evidence on this point, but short of already having a better taxonomy, it is hard to imagine what the evidence could be. Since one has to start someplace, one starts by …