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<Paper uid="C94-2145">
  <Title>ON TIIE PORTABILITY OF COMPLEX CONSTRAINT-BASED GRAMMARS</Title>
  <Section position="2" start_page="0" end_page="0" type="intro">
    <SectionTitle>
1 Introduction
</SectionTitle>
    <Paragraph position="0"> \]{.ec('.nt years have seen tile appearance of' a number of grammar f'ormalisms 1 sharing a strong family resemblance, which we have characterised elsewhere \[R,upp et al., 199d\] as tim property of being constraint-based.</Paragraph>
    <Paragraph position="1"> As well as having in common many formal properties, these formalisms also support, often by explicit de.sign, descriptions from a similarly convergent range o\[' linguistic theories, which we might reasonably label &amp;quot;\[lPSG-like&amp;quot;.</Paragraph>
    <Paragraph position="2"> Given the considerable common ground between such formalisms, it is reasonable to begin to ~sk questions about their intertranslatal)ility, or, ht programnling language terms, the relative ease with which it is possible to &amp;quot;port&amp;quot; a grammar from one such formalisnl to another. Such questious are clearly of interest \['or tile enterprise of recovering a.s much as possible of the existing stock of already encoded linguistic knowledge, perhaps for reuse in a more modern theoretical \['ramework. They are also of relevance for any attempts to build in portability from the start in ongoing new grammar writing.</Paragraph>
    <Paragraph position="3"> At present, the criteria for determining whether a particular translation is successful are extremely fuzzy.</Paragraph>
    <Paragraph position="4"> Apart from anything else, they will presumably depend to some extent on external goals, such as, for example, whether the results will be used in a practical, rnnning system or just in a laboratory experiment to show the feasibility of a particular theoretical approach. In our work, we have. a.ssulned that, if the translation is intended ,as more than a sterile exercise, then the information in the source description must be worth conserving and hence worth translating. Moreover, we suppose that the resulting target gramInar will need to be maintained and extendcd, and hence should be well-understood and well-behaved. Given these assumptions, we can begin to impose some conditions on what constitutes a &amp;quot;good&amp;quot; translation; in effect, in a translation from grammar A to grammar B: *Currently affiliated to the Institute for Computational IAnguistics, University of Stuttgart, Azenbergstr.12, 70174 Stuttgart, Germany, cj(~ims.mfi-stuttgart.dc ) In the interests of brevity, we shall often use the term grammar to refer to the collection of formal devices which comprise all aspects of a linguistic description, encomn&amp;sslng both grammaticM and lexical inforrn,~tion. This is purely a notational convenience and in no way implies a commitment to the primacy of syntax.</Paragraph>
    <Paragraph position="5"> * B and A should have the same input-output behaviour. null * B should conserve as much as possible of the conceptual shape of A.</Paragraph>
    <Paragraph position="6"> * B should have comparable or better run-time performance with respect to A.</Paragraph>
    <Paragraph position="7"> The first condition is a consequence, if somewhat oversimplified, of tile assumptions we made above, that the main purpose of the exercise is to preserve usefltl information.</Paragraph>
    <Paragraph position="8"> The second condition h~Ls to do with the relative expressivity of tile two formalisms involved. In effect, tLow much of the conceptual and organisatioual structure of a linguistic description can pass over un-. changed, and to what extent do conceptual changes that may have to be made obscure our subsequent understanding of the description as a whole? The question of performance is not limited to the relative execution speed of source and target grammars, though its importance for subsequent maintenance and development cannot be overstated, llow do we approach the case, for example, where the source grammar runs normally in its native environment but the translated form fails to terminate unless the description is completely restructured? And what if the two systems use conflicting criteria for the apportionment of procedural control between the linguist and the implementation? Over the past year, we have been engaged on a nun&gt; bet of experiments designed to investigate these portability issues, and in particular to bring out the implications behind the two related sets of questions about expressivity and performance. In some ways, our work is similar in spirit to the reusability experiments reported in \[Arnold el al., 1993\], though these appear to have been limited to translation to a single, rather general formalism, and to have been concerned ahnost entirely with questions of relative expressivity.</Paragraph>
    <Paragraph position="9"> The remainder of this paper discusses our own experinrents and comlnents ou some of our more important findings so far.</Paragraph>
    <Paragraph position="11"/>
  </Section>
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