Modelling Contractual Arguments

Chris Reed & Aspassia DaskalopuluDepartment of Information Systems and ComputingBrunel University, UK.E-mail: { Aspassia.Daskalopulu, Chris.Reed}@brunel.ac. uk1. INTRODUCTIONOne influential approach to assessing the “goodness” of arguments is offered bythe Pragma-Dialectical school (p-d) (Eemeren & Grootendorst 1992). This can becompared with Rhetorical Structure Theory (RST) (Mann & Thompson 1988), anapproach that originates in discourse analysis. In p-d terms an argument is good if itavoids committing a fallacy, whereas in RST terms an argument is good if it is coherent.RST has been criticised (Snoeck Henkemans 1997) for providing only a partiallyfunctional account of argument, and similar criticisms have been raised in the NaturalLanguage Generation (NLG) community—p articularly by Moore & Pollack (1992)—with regards to its account of intentionality in text in general.Mann and Thompson themselves note that although RST can be successfullyapplied to a wide range of texts from diverse domains, it fails to characterise some typesof text, most notably legal contracts. There is ongoing research in the ArtificialIntelligence and Law community exploring the potential for providing electronic supportto contract negotiators, focusing on long-term, complex engineering agreements (see forexample Daskalopulu & Sergot 1997). The negotiation process, which is a lengthy cycleof proposal and counter-proposal, can be seen as inherently argumentative in nature witheach party involved trying to influence the agreement in a way that best serves their owninterests. The negotiation process is conducted by parties exchanging proposed drafts ofthe contract, where each draft represents an argument put forward by one party topersuade the other. Furthermore the internal structure of any given contractual documentcan be analysed as an implicit discussion where an implicit opponent makes requests forclarification and specification (particularly of contingencies that might arise). Supportingthese aspects of contracts depends upon a rich model of the argumentative structure ofthe complex pre-contractual documents, and it is therefore disappointing that RST failsto account for such text.It has also become clear (Reed 1998) that RST is fundamentally inappropriatefor representing argument structure in three important respects: RST admits multipleanalyses of a given piece of text and this is in direct contrast to the argumentationtheoretic approach; particular structures that are frequently encountered in arguments arenot catered for by RST; and finally, patterns of reasoning that underlie an argument(such as modus ponens, inductive generalisation and so on) can neither be representedby, nor inferred from an RST analysis (and even more so where multiple analyses exist). This paper provides a brief introduction to RST and illustrates its shortcomingswith respect to contractual text. An alternative approach for modelling argumentstructure is presented (extending Reed & Long 1997a) which not only caters forcontractual text, but also overcomes the aforementioned limitations of RST. Finally it isshown that this approach meets the criticisms expressed by both Snoeck Henkemans(1997) and Moore and Pollack (1992) by offering a truly functional account ofillocutionary purpose.