Natural languages and context-free languages
Purchase on Springer.com
$39.95 / €34.95 / £29.95*
Rent the article at a discountRent now
* Final gross prices may vary according to local VAT.
Notice that this paper has not claimed that all natural languages are CFL's. What it has shown is that every published argument purporting to demonstrate the non-context-freeness of some natural language is invalid, either formally or empirically or both.18 Whether non-context-free characteristics can be found in the stringset of some natural language remains an open question, just as it was a quarter century ago.
Whether the question is ultimately answered in the negative or the affirmative, there will be interesting further questions to ask. If it turns out that natural languages are indeed always CFL's, it will be reasonable to ask whether this helps to explain why speakers apparently recognize so quickly whether a presented utterance corresponds to a grammatical sentence or not, and to associate structural and semantic details with it. It might also be reasonable to speculate about the explanation for the universally context-free character of the languages used by humans, and to wonder whether evolutionary biological factors are implicated in some way (Sampson (1979) could be read in this light). And naturally, it will be reasonable to pursue the program put forward by Gazdar (1981, in press) to see to what extent CFL-inducing grammatical devices can be exploited to yield insightful descriptions of natural languages that capture generalizations in revealing ways.
If a human language that is not a CFL is proved to exist, on the other hand, a different question will be raised: give the non-context-free character of human languages in general, why has this property been so hard to demonstrate that it has taken over twenty-five years to bring it to light since the issue was first explicitly posed? If human languages do not have to be CFL's, why do so many (most?) of them come so close to having the property of context-freeness? And, since the CFL's certainly constitute a very broad class of mathematically natural and computationally tractable languages, what property of human beings or their communicative or cognitive needs is it that has caused some linguistic communities to reach beyond the boundaries of this class in the course of evolving a linguistic system?
Either way, we shall be interested to see our initial question resolved, and further questions raised. One cautionary word should be said, however, about the implications (or lack of them) that the answer will have for grammatical studies. Chomsky has repeatedly stated that he does not see weak generative capacity as a theme of central importance in the theory of grammar, and we agree. It is very far from being the case that the recent resurgence of interest in exploring the potential of CF-PSG or equivalent systems will, or should, be halted dead in its tracks by the discovery (if it is ever forthcoming) that some natural language is not a CFL. In the area of parsing, for instance, it seems possible that natural languages are not only parsed on the basis of constituent structure such as a CF-PSG would assign, but are parsed as if they were finite state languages (see Langendoen (1975) and Church (1980) for discussion along these lines). That is, precisely those construction-types that figure in the various proofs that English is not an FSL appear to cause massive difficulty in the human processing system; the sentences crucial to the proofs are for the most part unprocessable unless they are extremely short (yet the arguments for English not being and FSL only go through if length is not an issue). This means that in practice properties of finite state grammars are still of great potential importance to linguistic theory despite the fact that they do not provide the framework for defining the total class of grammatical sentences. The same would almost certannly be true of CF-PSG's if they were shown to be inadequate in a similar sense. It is highly unlikely that the advances made so far in far in phrase structure description could be nullified by a discovery about weak generative capacity. Moreover, there are known to be numerous ways in which the power of CF-PSG's can be marginally enhanced to permit, for example, xx languages to be generated without allowing anything like the full class of recursively enumerable or even context-sensitive languages (see Hopcroft and Ullmann (1979), Chapter 14) for an introduction to this topic, noting especially Figure 14.7 on p. 393. The obvious thing to do if natural languages were ever shown not to be CFL's in the general case would be to start exploring such minimal enhancements of expressive power to determine exactly what natural languages call for in this regard and how it could be effectively but parsimoniously provided in a way that closely modelled human linguistic capacities.
In the meantime, it seems reasonable to assume that the natural languages are a proper subset of the infinite-cardinality CFL's until such time as they are validly shown not to be.
- AhoA. V. and J. D.Ullmann: 1972, The Theory of Parsing, Translation and Compiling, Volume I: Parsing (Prentice-Hall, Englewood Cliffs, New Jersey).
- AhoA. V. and J. D.Ullmann: 1973, The Theory of Parsing, Translation and Compiling, Volume II: Translation and Compiling (Prentice-Hall, Englewood Cliffs, New Jersey).
- AkmajianA. and F.Heny: 1975, An Introduction to the Principles of Transformational Syntax (MIT Press, Cambridge, Mass.).
- AllertonD. J.: 1980, Essentials of Grammatical Theory (Routledge and Kegan Paul, London).
- BachE.: 1974, Syntactic Theory (Holt Rinehart and Winston, New York).
- Bar-HillelY. and E.Shamir: 1960, ‘Finite State Languages: Formal Representations and Adequacy Problems’, reprinted in Y. Bar-Hillel (1964), Language and Information (Addison-Wesley, Reading, Mass.), pp. 87–98.
- BonvillainN.: 1974, ‘Noun Incorporation in Mohawk’, in M. K.Foster (ed.), Papers from the 1972 Conference on Iroquoian Research (National Museum of Man, Ottawa, Canada), pp. 18–26.
- Bonvillain, N. and B. Francis: 1980, ‘The Bear and the Fox, in Akwesasne Mohawk’, in Mithun and Woodbury (eds.), pp. 77–95.
- BresnanJ. W.: 1976, ‘Evidence for a Theory of Unbounded Transformations’, Linguistic Analysis 2, 353–393.
- BresnanJ. W.: 1978, ‘A Realistic Transformational Grammar’, in M.Halle, J. W.Bresnan, and G. A.Miller (eds.), Linguistic Theory and Psychological Reality (MIT Press, Cambridge, Mass.).
- Chomsky, N.: 1956, ‘Three Models for the Description of Language’, I.R.E. Transactions on Information Theory, Volume IT-2, Proceedings of the Symposium on Information Theory, September, pp. 113–123.
- ChomskyN.: 1963, ‘Formal Properties of Grammars’, in R. D.Luce, R. R.Bush, and E.Galanter (eds.), Handbook of Mathematical Psychology, Volume II (John Wiley, New York).
- ChomskyN.: 1977, ‘On Wh-Movement’, in P.Culicover, T.Wasow, and A.Akmajian (eds.), Formal Syntax (MIT Press, Cambridge, Mass.).
- ChomskyN.: 1981, Lectures on Government and Binding (Foris, Dordrecht).
- Church, K. W.: 1980, On Memory Limitations in Natural Language Processing, MSc Dissertation, MIT, Cambridge, Mass.
- CornulierB.de: 1973, ‘But If “Respectively” Meant Something?’, Papers in Linguistics 6, 131–134.
- CulicoverP. W.: 1976, Syntax (Academic Press, New York).
- DalyR. T.: 1974, Applications of the Mathematical Theory of Linguistics (Mouton, The Hague).
- ElsterJ.: 1978, Logic and Society: Contradictions and Possible Worlds (John Wiley, New York).
- FidelholtzJ.: 1975, Review of J. Kimball, The Formal Theory of Grammar, Language 51, 493–499.
- FodorJ. A.: 1975, The Language of Thought (Thomas Crowell, New York).
- FromkinV. and R.Rodman: 1978, An Introduction to Language, Second Edition (Holt Rinehart and Winston, New York).
- GazdarG.: 1980, ‘A Phrase Structure Syntax for Comparative Clauses’, in T.Hoekstra, H.van derHulst and M.Moortgat (eds), Lexical Grammar (Foris Publications, Dordrecht), pp. 165–179.
- GazdarG.: 1981, ‘Unbounded Dependencies and Coordinate Structure’, Linguistic Inquiry 12, 155–184.
- Gazdar G.: (in press). ‘Phrase Structure Grammar’, in P. Jacobson and G. K. Pullum (eds.), The Nature of Syntactic Representation (D. Reidel, Dordrecht, Holland).
- GazdarG., G. K.Pullum, and I. A.Sag: 1981, Auxiliaries and Related Phenomena in a Restrictive Theory of Grammar (Indiana University Linguistics Club, Bloomington, Ind.).
- GreenG. M.: 1971, ‘Unspeakable Sentences, Book I’, Linguistic Inquiry 2, 560.
- GrinderJ. T. and S. H.Elgin: 1973, Guide to Transformational Grammar (Holt Rinehart and Winston, New York).
- HintonG.: 1978, ‘Respectively Reconsidered’, Pragmatics Microfiche 3.3, 912–914.
- HopcroftJ. and J. D.Ullmann: 1979, Introduction to Automata Theory, Languages and Computation (Addison-Wesley, Reading, Mass.).
- HurfordJ. R.: 1980, ‘Generative Growing Pains’, Lingua 50, 117–153.
- HuybregtsM. A. C.: 1976, ‘Overlapping Dependencies in Dutch’, Utrecht Working Papers in Linguistics 1, 24–65.
- JohnsonD. E. and P. M.Postal: 1980, Arc Pair Grammar (Princeton University Press, Princeton, N.J.).
- KimballJ.: 1973, The Formal Theory of Grammar (Prentice-Hall, Englewood Cliffs, New Jersey).
- LangendoenD. T.: 1975, ‘Finite State Parsing of Phrase-Structure Languages and the Status of Readjustment Rules in the Grammar’, Linguistic Inquiry 6, 533–554.
- LangendoenD. T.: 1977, ‘On the Inadequacy of Type-3 and Type-2 Grammars for Human Languages’, in P. J.Hopper (ed.), Studies in Descriptive and Historical Linguistics: Festschrift for Winfred P. Lehmann (John Benjamin, Amsterdam, Holland), pp. 159–171.
- LangendoenD. T. (1981), ‘The Generative Capacity of Word-formation Components’, Linguistic Inquiry 12, 320–322.
- LeveltW. J. M.: 1974, Formal Grammars in Linguistics and Psycholinguistics, Volume II: Applications in Linguistic Theory (Mouton, The Hague, Holland).
- LounsburyF.: 1953, Oneida Verb Morphology (Yale University Publications in Anthropology, No. 48, Yale University, New Haven, Conn.).
- McCawleyJ. D.: 1968, ‘The Role of Semantics in a Grammar’, in E.Bach and R. T.Harms (eds.) Universals in Linguistic Theory (Holt Rinehart and Winston, New York).
- Michelson, K.: 1980, ‘Mohawk Text: The Edge of the Forest revisited’, in Mithun and Woodbury (eds.), pp. 26–40.
- MithunM. and H.Woodbury (eds.): 1980, Northern Iroquoian Texts (IJAL Native American Texts Series, No. 4) (University of Chicago Press, Chicago/University Microfilms International, Ann Arbor, Mich.).
- PinkerS.: 1979, ‘Formal Models of Language Learning’ Cognition 7, 217–283.
- Postal, P. M.: 1962, Some Syntactic Rules in Mohawk, Doctoral Dissertation (Yale University, New Haven, Conn.; Published by Garland, New York, 1979).
- PostalP. M.: 1964, ‘Limitations of Phrase Structure Grammars’, in J. A.Fodor and J. J.Katz (eds.), The Structure of Language: Readings in the Philosophy of Language (Prentice-Hall, Englewood Cliffs N.J.), pp. 137–151.
- ReichP. A.: 1969, ‘The Finiteness of Natural Language’, Language 45, 831–843.
- SampsonG.: 1975, The Form of Language (Weidenfeld and Nicolson, London).
- SampsonG.: 1979, ‘A Non-Nativist Account of Language Universals’, Linguistics and Philosophy 3, 99–104.
- SelkirkE. O.: 1977, ‘Some Remarks on Noun Phrase Structure’, in P. W.Culicover, T.Wasow and A.Akmajian (eds.), Formal Syntax (Academic Press, New York), pp. 285–316.
- Wachtel, T.: 1981, ‘Sex and the Single Pronoun’, unpublished paper (University of Warsaw).
- WinogradT.: 1972, Understanding Natural Language (Academic Press, New York). Also Cognitive Psychology 3, No. 1 (1972).
- WoodburyH.: 1975, ‘Onondaga Noun Incorporation: Notes on the Interdependence of Syntax and Semantics’, International Journal of American Linguistics 41, 10–20.
- ZaenenA.: 1979, ‘Infinitival Complements in Dutch’, Papers from the Fifteenth Regional Meeting (Chicago Linguistic Society, Chicago, Ill.), pp. 378–389.
- ZwickyA. M.: 1963, ‘Some Languages That Are Not Context-free’, Quarterly Progress Report of the Research Laboratory of Electronics, MIT, 70, 290–293.
- Natural languages and context-free languages
Linguistics and Philosophy
Volume 4, Issue 4 , pp 471-504
- Cover Date
- Print ISSN
- Online ISSN
- Kluwer Academic Publishers
- Additional Links