Mach Translat (2008) 22:175–180DOI 10.1007/s10590-009-9049-6

BOOK REVIEW

Khurshid Ahmad, Christopher Brewster, MarkStevenson (Eds), Words and Intelligence I: SelectedPapers by Yorick WilksSpringer, 2007, xii+280p.

Joseba Abaitua

Received: 28 October 2008 / Accepted: 6 March 2009 / Published online: 1 April 2009© Springer Science+Business Media B.V. 2009

This compilation of papers by Yorick Wilks must be recommended to every libraryspecialised in machine translation, computational linguistics, or artificial intelligence.It really looks like a Festschrift to Yorick, has he retired? The compilation waspresented in 2007 to the British Computer Society in London along with anothervolume of essays in his honour (also edited by Ahmad, Brewster and Stevenson,2007b). At the LREC’2008 conference in Marrakech Yorick Wilks was awarded theAntonio Zampolli prize and the Lifetime Achievement Award only a few weeks laterat the ACL’2008 conference in Columbus (USA). These seem unmistakable signsof retirement tributes. However, it is difficult to believe that a talented, active andprolific scholar as Yorick will come to terms with a definite break. A more thoroughharvest of news on the web rapidly shows that he has not: the recent (January 2007)attained fellowship at Oxford Internet Institute, together with the coordination of thefour year (2006–2010) e10,178,219 FP6 funded project are unmistakable evidenceof null withdrawal. Moreover, we can see that he has been particularly active in orga-nizing seminars and workshops; five, in only the last four years on topics as wide andup to date as: Artificial Companions, Oxford Internet Institute, 2008; Emotions andLanguage (with Prof. K Ahmad), Marrakesh, Morocco, 2008; Literature and LanguageProcessing (with Roberto Basili), Genoa, 2006; Making Sense of Sense (with NancyIde) Trento, 2006; Modern Approaches in Translation Technologies, Bulgaria, 2005.

Professor Wilks’ latest project (EU Companion) aims at developing “a persona-lised, persistent, Internet agent” and surely is the greatest chance to put into practicehis lifelong research in the two main topics of dialogue management and natural lan-guage understanding. I would argue precisely that the book reviewed contains thebasic set of papers needed for a complete picture of Wilks’ approach to both topics:

J. Abaitua (B)Department of Modern Languages, University of Deusto, 48080 Bilbao, Spaine-mail: joseba.abaitua@gmail.com

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the framework of preferential semantics. It has been indeed a pioneering and veryinfluential technique in the field of artificial intelligence, particularly during the 1970sand early 1980s. As it is epitomised in Wikipedia (by whom I believe is an authorisedcontributor), the approach provides an “algorithmic method for assigning the ‘mostcoherent’ interpretation to a sentence in terms of having the maximum number ofinternal preferences of its parts (normally verbs or adjectives) satisfied. […] A keycomponent was that the interpretation of an utterance is not a well- or ill-formed notion,as was argued in Chomskyan approaches, such as those of Fodor and Katz, but ratherthat a semantic interpretation was the best available, even though some preferencesmight not be satisfied. […] preference semantics is thus some of the earliest com-putational work—with programs run at Systems Development Corporation in SantaMonica in 1967 in LISP on an IBM360—in the now established field of word sensedisambiguation” and shallow parsing, I would like to add.

Six out of the eleven papers contained in the book are devoted to the presentationof preferential semantics. All these six papers were written in the 1970s:

• “Decidability and Natural Language” (in Mind, 1971). This is a debate on thetheoretical possibility of representing the meaning of language in a computableway. It poses the fundamental claim of Wilks’ semantic model: if there is at leastone possible interpretation for a sentence, not in terms of truth values, but ofpreferred meanings, then it should be found and made explicit. The papercontains a deep and erudite exposition of the problem of meaning representation,with references to known thinkers as Spinoza, Carnap, Wittgenstein, Gödel, Quineand Chomsky, to name just a few. Since his early scholarly days (he was 32 whenthe paper was published) Wilks has never feared to deal with technical aspectsfrom their deepest theoretical implications. In this paper, Wilks sustains the lateWittgensteinian view that he has kept to present: the meaning of linguistic itemssuch as words cannot be defined as abstract or Platonic entities outside language.Instead he proposes a set of more basic linguistic entities on top of which more com-plex semantic representations can be constructed. He also denies the hypothesisof treating syntactic and semantic representation of natural language utterancesas independent artefacts. He gives semantics a more essential role and the mainproblem would be to prove whether there is a deterministic procedure to decide themeaningfulness of sentences or not.

• “The Stanford Machine Translation and Understanding Project” (in Natural Lan-guage Processing, edited by R. Rustin in 1973). With an interlingual approachto MT in the background, Wilks shows a practical implementation of his pro-posal for semantic parsing and generation without going through the conventionalsyntactic analysis stage. Input English sentences are directly mapped into semanticrepresentations in the form of text templates, from which French target sentencesare later generated. Wilks displays the working artefact from a pure engineeringpoint of view discarding more refined representation models, such as Montague’sor Lakoff’s model theories, which he cites without discussion (something that israre in Wilks papers). The Stanford MT project and this paper, published onlyseven years after the 1966 ALPAC report, can be regarded as a straight reaction

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to the major handicap for MT that had been mentioned by scholars as Minsky orBar-Hillel: in order to achieve fully automatic high-quality machine translation(FAHQMT), machines must be able to process meaning. Perhaps that explainsWilks’ strong assertion about the role of syntax: “At this time, it is easy to beunfair to the memory of that early MT work and to exaggerate the simplicity ofits assumptions about language. But the fact remains that almost all of it was doneon the basis of naïve syntactic analysis and without the use of any of the develop-ments in semantic structuring and description that have been noteworthy featuresof recent linguistic advances”. However, his faith on a solely semantic means toovercome the MT challenge, from a modern perspective, also seems innocent.Wilks truly believed that a finite inventory of templates made up of a fixed numberof word sense formulas would be enough to translate any fragment of English intoFrench. The Stanford experiment was no more than a mere demo system, designedto illustrate the resolution of a few translation issues, as it was typically the case inthe 1970s and early 1980s.

• “An Intelligent Analyser and Understander of English” (in Communications of theACM 18, 1975). This paper further develops the application of preference semanticsto MT. It provides more detailed explanation about the composition of word-senseformulae into text templates. More importantly, it introduces the precise 70 primi-tive semantic elements that make it possible to “express the semantic entities, states,qualities, and actions about which humans speak and write”. These form a micro-language in which more complex concepts can be expressed. Semantic preferencesare defined along the lines of selectional restrictions, but with a very important for-mal difference. While the latter are constraints that have to be satisfied, the formerfunction as paradigmatic cases, indicating only common or prototypical favouredmeaning interpretations. The system will try to fulfil as many of these prototyp-ical interpretations as possible, but will not fail if some are not. The checking ofpreferences relays on the semantic primitives elements that had been listed earlier.Wilks shows how syntactic and semantic parsing can be carried out in parallel,contrary to standard practices of the time, suggesting that semi-parsing (shallowparsing?) may be sufficient to support well defined semantic representations andthat “heavily hierarchical syntax analysis may not be necessary”, a remarkableprophetic statement that predated the rise and fall of formal grammars in NLPparsing.

• “A Preferential, Pattern Seeking, Semantics for Natural Language Interface” (inArtificial Intelligence 6, 1975). This paper climbs one step further on the prac-tical implementation of preference semantics by applying it to the resolution ofanaphoric references. Because a language understanding system should alwaysprovide a possible interpretation of a sentence, the system attempts to resolve awide range of anaphora, making the best guess about the meaning of an utterance,as a human does, and act accordingly.

• “Good and Bad Arguments about Semantic Primitives” (in Communication andCognition 10, 1977) . In this paper, Wilks undertakes the discussion on the nature

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of semantic primitives, what they really mean and what kind of semantics theystand for. Arguments from leading authors of the time, such as Charniak (1975),Hayes (1974), Putman (1970) or Bobrow and Winograd (1977) are reviewed. Thetopic of semantic primitives is very appealing and Wilks does not fail to satisfyour expectations. In order to demonstrate how useful they are for constructingmeaningful representations of natural language, he provides an instructive appen-dix in which he not only defines explicit formulae (to account for nominal, verbal,adjectival or adverbial expressions) but also he uncovers the exact essence of suchprimitive elements. The author provides the complete list of cases (19), actions(34), substantives (19), classes (12), and qualifiers (16). It is important to pointout the Wittgensteinian nature of such elements, since they do not belong to anabstract, platonic system of symbols but are within natural language itself and donot necessarily lead to universal generalization across language boundaries, normore than one language would need to be translatable into them. The last lines ofthe paper anticipate what it would become a major focus of research some yearslater: “actual statistical analysis of large dictionaries reveals that their definitionsare, in fact, in terms of a restricted sub-vocabulary, to a large extent, and that thisis close to a natural set of primitives”.

• “Making Preferences More Active” (in Artificial Intelligence 11, 1979). This lastpaper on preference semantics shows the application of the framework to a widerrange of linguistic phenomena, and in particular to the resolution of metaphor.According to the author, metaphorical expressions are clear evidence of the needof world knowledge. These also confirm the shortcomings of most formal methodsof language representation advocated at the time.

The remaining papers represent five crucial moments in Wilks’ trajectory and are,excluding the 1964 paper, from the 1990s:

• “Text Searching with Templates” (Memo at Cambridge Language Research Unit,1964), published when he was only 25, is an early and illuminating technical reportin which Wilks sketches the use of templates for meaning representation that laterbecame one of his essential mechanisms of preference semantics.

• “Providing Machine Tractable Dictionary Tools” (in Machine Translation 5, 1990).The decade of the 1990s shows a sharp transformation of the methods applied tonatural language processing. Large language resources are put into action andstatistical techniques applied in their exploitation. Machine-readable dictionaries(MRD) become an important resource for extracting large lexicons and the papershows the conclusions of the work he led while he was director of the ComputerResearch Lab (CRL) at New Mexico State University in Las Cruces (1985–1993).Word co-occurrences within dictionary definitions are statistically analysed whichallow for the automatic detection of word senses. The paper shows also how toconvert MRD into a format ready for machine uses: machine-tractable dictionaries(MTD). Wilks takes advantage of this process to test his historic ideas of seman-tic primitives and poses the objective of discovering the core set of basic termsused in the definitions, his ultimate intention being the generation of lexical entries

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for a preference semantic system that would overcome the dependence on manuallabour-intensive means.

• “Belief Ascription, Metaphor and Intensional Identity” (in Cognitive Science 15,1991) is a long and thoughtful paper in which Wilks takes up again the interpretationof metaphor that he had studied within preference semantics. In this occasion heapproaches the problem in the context of a dialogue understanding system (View-Gen), an AI agent capable of reasoning about the propositional attitudes, such asdesires, intentions and beliefs, of other agents present in the discourse. The authorshows familiarity with the state of the art (represented by various works cited:Ballim (1987), Barnden (1989), Cowie et al. (1992), Grosz (1977), Hobbs (1983),and others) and as in other occasions shows a strong engineering bias, looking forpractical and efficient algorithms instead of “adequate proof procedures or elegantaxiom sets”. Wilks’ ability in dialogue modelling was demonstrated only a fewyears later, in 1997, when he collaborated with a team lead by David Levy to winthe Loebner Prize, an annual competition that gives an award to the most humanlikechatterbot.

• “Stone soup and the French Room” (in Current Issues in Natural Language Pro-cessing: In Honour of Don Walker, edited by Zampoli, Calzolari and Palmer, 1994).An interesting and controversial article celebrating the launch by IBM of the CAN-DIDE translation system based on statistics. Wilks shows a sceptical view of thepossibilities of pure data-driven techniques devoid of any kind of linguistic infor-mation. He makes clear that he does not oppose empirical approaches to naturallanguage processing, and evokes the earliest attempts made in computational lin-guistics when statistical methods were also tested. According to Ahmad, Brewsterand Stevenson, “Yorick’s claims have been proved by recent work on statisticalmachine translation and during the decade or so since this paper was publishedwork on statistical machine translation has gradually moved towards the increas-ingly rich linguistic structures combined with data derived from text”.

• “Senses and Texts” (in Computers and the Humanities, 1997). The paper containsa critical review of major work on word sense disambiguation being carried outin the early 1990s, including that of Brown et al. (1991), Cowie et al. (1992), Galeet al. (1992), Yarowsky (1993) and others, as well as a discussion as to what extentword senses are discrete (Jorgensen 1990; Kilgarriff 1993). For several years thistopic has played a prominent place in computational linguistics, attracting alsoWilks’ own interest. One main motivation behind preference semantics was therecognition of metaphorical expressions and other word usages that were differentfrom the standard meanings acknowledged in dictionaries. Advances in the fieldare, however, hindered by the diverse ways and resources employed, ranging fromunannotated parallel corpora to bilingual dictionaries, thesauri as well as texts fromencyclopaediae. Wilks stresses the fluctuation of the notion of word sense and con-cludes with one of his typical ironical and witty paradoxes: “that sense-tagging ofcorpora cannot be done, and that it has been solved. As many will remember, MTlived both these, ultimately misleading, claims for many years”.

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In sum, all the eleven compiled papers exude Yorick Wilks’ splendid and talentedcontributions to the major issues of language technology and machine translationduring the three vital decades extending from 1964 to 1997. The book certainly is anecessary tribute to the author’s lively legacy.

References

Ahmad K, Brewster C, Stevenson M (eds) (2007a) Words and intelligence I: selected papers by YorickWilks. Springer, Dordrecht

Ahmad K, Brewster C, Stevenson M (eds) (2007b) Words and intelligence II: essays in honour of YorickWilks. Springer, Dordrecht

Ballim A (1987) The subjective ascription of belief to agents. In: Hallam J, Mellish C (eds) Advances inartificial intelligence. Wiley, Chichester, UK

Barnden JA (1989) Towards a paradigm shift in belief representation methodology. J Exp Theor Artif Intell1:131–161

Bobrow D, Winograd T (1977) An overview of KRL: a knowledge representation language. Cogn Stud1:3–46

Brown PF, Di Pietra SA, Di Pietra VJ, Mercer RL (1991) Word sense disambiguation using statisticalmethods. In: Proceedings of the 29th annual meeting of the Association for Computational Linguis-tics, Berkeley, CA, pp 261–270

Charniak E (1975) Organization and inference. In: Proceedings of the Conference on Theoretical Issues inNatural Language Processing. The MIT Press, Cambridge, MA, pp 42–51

Cohen P, Levesque H (1985) Speech acts and rationality. In: Proceedings of the 23rd annual meeting of theAssociation for Computational Linguistics. University of Chicago, pp 49–60

Cowie JL, Guthrie L, Guthrie J (1992) Lexical disambiguation using simulated annealing. In: Proceedingsof COLING, pp 359–365

Gale W, Church K, Yarowsky D (1992) One sense per discourse. In: Proceedings of the DARPA Workshopon Speech and Natural Language, Harriman, NY, pp 233–237

Grosz BJ (1977) The representation and use of focus in a system for understanding dialogs. In: Proceedingsof the 5th International Conference on Artificial Intelligence. Cambridge, MA, pp 67–76

Hayes P (1974) Some issues and non-issues in representation theory. In: Proceedings of the AISB SummerConference. University of Sussex, Sussex, pp 63–79

Hobbs JR (1983) Metaphor interpretation as selective inferencing: Cognitive processes in understandingmetaphor. Empir Stud Arts 1(1):17–34

Jorgensen J (1990) The psychological reality of word senses. J Psycholinguist Res 19:167–190Kilgarriff A (1993) Dictionary word sense distinctions: an enquiry into their nature. Comput Humanit

26:365–387Putman H (1970) Is semantics possible. Metaphilosophy 1:187–201Yarowsky D (1993) One sense per collocation. In: Proceedings of the ARPA Human Language Technology

Workshop, Princeton, NJ, pp 266–271Wilks Y (2009) In: Wikipedia, the free encyclopedia. Retrieved March 3, 2009 at http://en.wikipedia.org/

w/index.php?title=Yorick_Wilks&oldid=261889889

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