Báo cáo khoa học: "Structural Grammars"

Chia sẻ: Nghetay_1 Nghetay_1 | Ngày: | Loại File: PDF | Số trang:6

Thêm vào BST

Báo xấu

59
lượt xem 1
download

Download Vui lòng tải xuống để xem tài liệu đầy đủ

We adopt the view that the grammar of a language is a predictive theory which isolates the grammatical sentences of that language by means of immediate constituent analyses, morphophonemic conversions, and grammatical transformations.

Chủ đề:

Bình luận(0) Đăng nhập để gửi bình luận!

Lưu

Nội dung Text: Báo cáo khoa học: "Structural Grammars"

[Mechanical Translation, vol.4, nos.1 and 2, November 1957; pp. 5-10] Structural Grammars† R. B. Lees, Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts We adopt the view that the grammar of a language is a predictive theory which iso- lates the grammatical sentences of that language by means of immediate constitu- ent analyses, morphophonemic conversions, and grammatical transformations. A sample grammatical analysis is given for the development of the verb phrase in German independent clauses. Simple rules are given for converting the verb phrase as a sequence of personal affixes, various auxiliaries, and the main verb into passive, future, or conditional clauses, and then introducing word boundaries, choosing the proper auxiliaries, arranging the word-order, and finally mapping the resulting morpheme sequence into the correct sequence of words in the inde- pendent clause. of class membership and must be devised dif- ANY reasonably general, mechanized program ferently for each language. Moreover, de- for translating texts from one language into an- scriptive sketches are deficient in their pres- o ther can avoid dealing with each and every entation of the syntax in that they are either s entence as a completely new and arbitrary fragmentary or else require very complicated, s equence of dictionary items only if it pro- arbitrary, and often-repeated rules for speci- v ides each source-language sentence with a fying the constituent structure of even fairly grammatical analysis. Simple sentences. This is largely the result Traditional notional or semantic-based o f assuming that all sentences of a natural grammatical descriptions are useless for this language are describable in terms of an im- purpose, since an analysis using such a gram- mediate-constituent analysis or branching- mar can be carried out only if the meanings of diagrams. all of the constituents of the sentence are given. N. Chomsky (1) has described a theory of lan- These meanings cannot be assumed: one of the guage which avoids these difficulties by relax- main purposes of a syntax program is to aid in a tion of requirements on a grammar to the determining them so that they can be trans- weaker position of satisfying some evaluation f erred, i.e., translated, into the appropriate procedures ( instead of requiring a discovery target-language equivalents. Furthermore, or decision procedure ), introduction of natural contemporary descriptive linguistic grammati- canons of simplicity or elegance, statement in cal practice is also faulty, especially when it terms of a set of expansion rules for generat- is to be employed in a machine program; for, ing all grammatical utterances, and, above all, while the descriptive linguist no longer desig- introduction of a level of grammatical trans- nates sentence constituents by means of mean- formations. These grammatical transforma- ing-labels but refers exclusively to their per- tions convert the constituent-structures of a ceptible shapes, the description is still largely set of the most central sentences ( i . e . , basic, ad hoc — each particular grammatical category nonderived sentence types, such as affirmative i s designated by an arbitrary stigma or mark assertions ) into the derived structures of a more complex, less central, and infinitely ex- tendible set of sentences. † This work was supported in part by the U.S. Army ( Signal Corps), the U.S. Air Force (Office of Scientific Research, Air Research 1. Chomsky, N., "The Logical Structure of and Development Command), and the U.S. Navy Linguistic Theory", Preliminary Draft, M.I.T., (Office of Naval Research); and in part by the 1956, 713 + li pp. National Science Foundation.
6 R.B. Lees long, but not obviously excluded, types will Following certain suggestions of Chomsky and Lukoff (2) a scheme has been constructed not be generated. b) There is no provision for conforming the as an illustration of a small, isolated portion affixes of the finite verb to those of the accom- of such a grammar for German. The scheme panying noun phrases in the sentence, or for is intended to generate all verb phrases of in- adjusting the selection between particular verb- dependent clauses, active and passive, subject phrase morphemes and other morphemes ex- to the following limitations: ternal to the verb phrase, such as subject, ob- a) The device generates several types of verb ject, or adverbial, or between the verb and the phrase which would occur only rarely in natu- separable prefix. ( This last selection would ral speech, not for any clearly grammatical devolve upon the lexicon. ) reason, but simply because they are too long c) No provisions are made to generate imper- or clumsy. Three types generated are proba- sonal constructions, zu- infinitives, nominal- bly only semigrammatical, containing two past ized verb phrases, dependent clauses, or other participles in ge-. In addition, several very verbal constructions. d) The rules for generating the proper allo- morphic shapes of the stems and affixes are 2. Chomsky, N. and Lukoff, F., "Construction only suggested by reference to a few examples, of the German Verb Phrase", Mechanical Trans- since a complete listing of morpheme spellings lation Group Memo, Aug. 12, 1955, Research would be as long as the lexicon. Laboratory of Electronics, M.I.T. GLOSSARY OF SYMBOLS
Structural Grammars 7 D EVELOPMENT OF THE VERB PHRASE 1. PHRASE-STRUCTURE RULE to yield verb phrases of kernel sentences 2. Optional GRAMMATICAL TRANSFORMATIONS to yield non-kernel sentences a . Passive transformation :
8 R.B. Lees 3. Obligatory MAPPINGS to yield proper word-order, word boundaries, and auxiliary selections
Structural Grammars 9
10 R. B. Lees A SAMPLE DERIVATION