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<Paper uid="J79-1007">
  <Title>OF CONTEXT FREE LANGUAGES</Title>
  <Section position="11" start_page="213" end_page="213" type="concl">
    <SectionTitle>
5. Conclusion and Further Research.
</SectionTitle>
    <Paragraph position="0"> At the present time what is needed more than anything else in the area of language translation is an understanding of the fonnal nature of semantics, its relation to syntax in language description, and its role in translation. I believe this paper provides some of the basis for that understanding. Incidentally, the reader might have observed that the definition of phrase-s tructure semantics in Section 1 provides for solutions to the semantic projection problem (cf Katz and Fodor (1964), and Langendoen (1969)) .</Paragraph>
    <Paragraph position="1"> The reqder is certainly aware by now, if not before, that thew are many grammars and semantics for a given language. After having played with writing grammars and semantics for simple languages for quite a while nov, I believe that, for most languages at least, there are &amp;quot;better&amp;quot;  grammars and semantics and worse&amp;quot; ones. Some just seem to be more  elegsnt or simple, or natural&amp;quot; than others, for a given language. But I can't say much of a specific nature about what it means for a grammar and It semantics to be &amp;quot;elegant&amp;quot;, &amp;quot;simple&amp;quot;, or natural&amp;quot;. It seems that some study ih this area might give us insight into certain skills for maklng it easier to write linguistic descriptions suitable for. translation. One phenomenon this model explains is why it is so difficult to compute an inverse translation and get anything like the original. That is, if one $tarts with sentence w in L and translates to w in L2, then  translates w' to w&amp;quot; back in L one would like for-w and w&amp;quot; to have the 1' same meaning. But the scutt1ebut.t says it isn't so, and this model shows why. Note that all that is requifed for T:  In ~der to get back to the original meaning, each translator must produce the entire set ~(w), rather than just some sentence in T (w), and then all of these must be retranslated in entirety. Translation programs don' t usually do that. Neither do human translators, for that matter! Alternatively, the translator should be able to give with the translation, its parse and the atomic morphemes associated with the sentence. The 7rocedure in this paper provides for doing that.</Paragraph>
    <Paragraph position="2"> The same definition of translation, if it is accurzte, also explains another phenomenon of language translat-ion -- haw it is that two very different translati~ns can corn from the same source.</Paragraph>
    <Paragraph position="3"> If wt and w&amp;quot; are translations or w, then we have ul(w) n p2(wt) f (b and ul(w) fl u2Cwff) C fi, but it doe; not follaw that p2(~') fl v2(wvt) # 8-For natural language, one would like t,opexte i the theory in this paper to arbitrary phrase structure grammars and to transformational grammars.</Paragraph>
    <Paragraph position="4"> The ewlarlsion to transformational gramanrs requires only  3-The &amp;quot;lore&amp;quot; has it that someone fed. the following sentence to a translator from L to Lp:  &amp;quot;The spirit indeed is will-ing, but the flesh is weak.&amp;quot; Then lie took the translation and fed it into a translator froui L, to L LI, and got: &amp;quot;The liquor is all right, but the meat is spoiled.&amp;quot; formalizing the notion of the transform pf a semantic function to be associated with each syntax transformation. (For transformational semantic theories which do not allow semantic change in the transformations, the extension to arbitrary phrase structure grammars is sufficient, of course.) The extension to arbitrary phrase structure grammars requires first a formal statement o.f the &amp;quot;phrase structures&amp;quot; of unrestricted grammars, since these structures are not trees. The author's forthcoming paper, listed in the bibliography, covers the subject of the syntactic structures for unrestricted languages in detail.</Paragraph>
    <Paragraph position="5"> There are, of course, schemes for translation other than: the one in this paper. One might think of computing the meaning of a source sentence, and then having some effective way of generating the target sentence directly from the meaning. The scheme in this paper, however, is more attractive at present than such a &amp;quot;direct&amp;quot; scheme, for three reasons: 1) It is intuitively satisfying. I believe I translate by first translating simple phrases and then putting their separate translations together according to some restructuring rules that are guaranteed to preserve seaantics . Thus, one &amp;quot;builds up&amp;quot; the translation of a sentence recursively. I am more likely to call the result which I get by first computing the whole meaning and then producing a sentence (often it is a sequence of sentences) with the same meaning, a &amp;quot;paraphrase&amp;quot; l I or an interpretation&amp;quot;, rather than a tft~anslation&amp;quot;. 2) If used much, thss scheme is likely to be more efficient than the &amp;quot;direct&amp;quot; scheme, since no-semantic computation is required at translate t-ime. AJl the semantic problems are examined once and for all in the translator generator; at translation time, only a sequence of tree mappings is performed - simply a structure matching and replacing technique. 3) The &amp;quot;direct&amp;quot; scheme requires knowing how to specify linkuistic descriptions in such a way that, given a meaning in semantic notation, one can produce a sentence having that meaning.</Paragraph>
    <Paragraph position="6"> This problem Ts a difficklt one not yet well understood.</Paragraph>
    <Paragraph position="7"> Presumably, the research currently under way in the f izld of generative semantics will explicate the issues involved.</Paragraph>
  </Section>
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