Defining the Semantics of Verbal Modifiers in the Domain of Cooking Tasks

Defining the Semantics of Verbal Modifiers in the Domain of Cooking Tasks Robin F. Karlin Department of Computer and Information Science University of Pennsylvania Philadelphia, PA 19104-6389 Abstract SEAFACT (Semantic Analysis For the Animation of Cooking Tasks) is a natural language interface to a computer-generated animation system operating in the domain of cooking tasks. SEAFACT allows the user to specify cooking tasks "using a small subset of English. The system analyzes English input and pro- duces a representation of the task which can drive motion synthesis procedures. Tl~is paper describes the semantic analysis of verbal modifiers on which the SEAFACT implementation is based. Introduction SEAFACT is a natural language interface to a computer-generated animation system (Karlin, 1988). SEAFACT operates in the domain of cooking tasks. The domain is limited to a mini-world con- sisting of a small set of verbs chosen because they involve rather complex arm movements which will be interesting to animate. SEAFACT allows the user to specify tasks in this domain, using a small subset of English. The system then analyzes the English input and produces a representation of the task. An intelli- gent simulation system (Fishwick, 1985,1987), which is currently being extended, will provide the final link between the SEAFACT representation and lower level motion synthesis procedures. The representation con- sists of a decomposition of verbs into primitive actions which are semantically interpretable by the motion synthesis procedures. It also includes default infor- mation for all knowledge which is not made explicit in the input, but must be explicit in the animated output. The representation contains sufficient non- geometric information needed to schedule task start and end times, describe concurrent actions, and pro- vide reach, grasp, and motion goals. An empirical, linguistic study of recipes was con- ducted with the goals of delimiting the scope of the cooking domain, identifying important verbal mod- ifiers, and defining the semantics of those modifiers. This paper is concerned primarily with describing the results of this study and the implementation of some of the modifiers. A Linguistic Analysis of Verbal Modifiers An empirical study of approximately II0 sentences from nine cookbooks was carried out. Verbal mod- ifiers were found to play an essential role in the ex- pressive power of these sentences. Therefore, in order to develop a representation for the verbal modifiers, the study describes and categorizes their occurences and provides a semantic analysis of each of the cate- gories. Each of the categories is considered a seman- tic role in the representation of the natural language input. Temporal adverbials were found to be partic- ularly prevalent in recipes because they are needed to specify temporal information about actions which is not inherent in the meaning of verbs and their ob- jects. This paper discusses two categories of temporal modifiers: duration and repetitions as well as speed modifiers. Other categories of modifiers which were analyzed include quantity of the object, end result, instrument, and force. Passonnean (1986) and Waltz (1981,1982) are con- cerned with developing semantic representations ad- equate …

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