On the Representation of Physical Quantities in Natural Language Text

Abstract

On the Representation of Physical Quantities in Natural Language Text Sven E. Kuehne (skuehne@northwestern.edu) Qualitative Reasoning Group, Northwestern University 1890 Maple Avenue, Ste. 300 Evanston, IL 60201, USA theory should be reflected in the language that people use to communicate their understanding of physical phenomena. This paper shows that the natural language descriptions of physical processes contain abundant information about the constituents of physical quantities. Moreover, the results of this study can be used in a variety of applications, such as grammatical rules of a parser or in the design of information extraction algorithms. 2 Abstract In this paper we investigate the forms in which quantity information can appear in written natural language. Our focus is on physical quantities found in descriptions of physical processes, such as expansion, movement, or transfer. Using Qualitative Process Theory as our underlying formalism, we show how information extracted from natural language text corresponds to the five constituents of physical quantities. The results of this analysis can be used for the creation of interpretation rules and extraction patterns in NL systems. Physical quantities Introduction Ordinary people know a lot about the physical world around them. They know that water will eventually boil if you heat it on a stove, that a ball placed at the top of a steep ramp will roll down, and that a cup will overflow if you continue to pour coffee in it. When people talk and write about such phenomena in everyday language, references to continuous properties are usually part of these descriptions. From simple utterances like “The coffee is hot” to a more complicated comparison like “The velocity of gas molecules is higher than the velocity of molecules in a liquid.” being able to identify and extract the information about physical quantities is essential to understand these sentences. Using Qualitative Process Theory (Forbus, 1984) as the underlying formalism, we investigate the forms in which continuous properties can appear in written natural language. Our focus is on physical quantities found in descriptions of physical processes, such as expansion, movement, or transfer. 1 The way in which continuous parameters and processes are described in natural language is not accidental. Since Qualitative Process Theory is a formalism of how people reason about the physical world, the basic ideas of the The findings of this analysis are applicable to other types of quantities as well. The framework of QP theory determines just determines kind of information we are interested in, i.e. constituents of a physical quantity. Abstract and conceptual quantities are often referred to metaphorically by words with a physical basis and require a different semantic interpretation. ‘The price is hot.’ is does not have anything to do with temperature, unlike ‘The water is hot.’ However, the techniques for the extraction of information about such quantities are essentially the same. In Qualitative Process Theory, all physical changes in continuous properties are caused by physical processes. The identification of continuous parameters is therefore an essential step in the extraction of information about physical processes from natural language text. In an earlier analysis (Kuehne & Forbus, 2002) we presented a scheme for the extraction process that uses FrameNet- compatible representations (Baker, Fillmore, & Lowe, 1998; Fillmore, Wooters, & Baker, 2001) to capture information about physical processes. The examples presented draw from the same corpus material (Buckley, 1979; Maton et al., 1994; Moran & Morgan, 1994) used in our previous analysis. Our goal here is to show how information about continuous parameters can appear in natural language, and the ways in which this information corresponds to the following five constituents of physical quantities: • The Entity is a uniquely named object or an instance of a process associated with the quantity. For example, the word ‘brick’ in the noun phrase ‘the temperature of the brick’ denotes an entity. 3 • The Quantity Type specifies the kind of parameter. The word ‘temperature’ in the noun phrase ‘the temperature of the brick’ is a reference to a quantity type. • The Value specifies the numerical or symbolic value of the property. The number ‘3’ in ‘3 liters of water’ or Although we use the results of the analysis for exactly these purposes, the findings are presented in a general way and not limited to any particular type of grammar or pattern language. The noun ‘brick’ actually refers a particular individual, maybe ‘brick32’, not the collection of all bricks.