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<Paper uid="C88-2150">
  <Title>Generation as Structure Driven Derivation</Title>
  <Section position="5" start_page="736" end_page="736" type="concl">
    <SectionTitle>
4 Acknowledgements
</SectionTitle>
    <Paragraph position="0"> The research reported in this paper was partially supported by the EUROTKA-I) accompanying research (BMFT grant No. 101 3207 0) and the ESPRIT project ACORD (project P393). The author would like to thank Mark Johnson, Bob Kasper, Stefan Mamma, Klaus Netter, Klaus Reinhardt and the members of the working group on Unification at the University of Stuttgart (Inge Bethke, Jochen DSrre, Andreas Eisele and ttenk Zeevat) who read carefully through earlier versions of this paper and helped a lot iu improving both the algorithm and its presentation. All remaining errors are of course my own.</Paragraph>
    <Section position="1" start_page="736" end_page="736" type="sub_section">
      <SectionTitle>
Footnotes
</SectionTitle>
      <Paragraph position="0"> depends on the domain of application how this ia done in a particular case, and since we want to demarche the algez-ithm independently of specific applications, we submit it to thi~ strong condition.</Paragraph>
      <Paragraph position="1"> SDetalled \[dormation on solution algorithms cent be found in \[Johnson 66\] and \[Johnson ST\].</Paragraph>
      <Paragraph position="2"> rI wa~ reminded by an anr~ymou~ reviewer to relate thi~ paper to a paper by Block (\[Block 80\]), who must have had this procedta.e In mind, when he claimed that there is no way to derive c-~tructures from f-structures.</Paragraph>
      <Paragraph position="3"> &amp;quot;On the other hand, an LFG grammar, which does not allow traamfonna~ tiers Is forced to generate on tv~ differ~tt level~ f-structure and c-structure and then to compa~ the two, \]ooklng for a rnatch~ This is tim case because the theory specifically forbids carrying out any operations on either f- or e-stzzlcttu~s (cf. Kaplan and Bresnan 1982:180). Thus, there is no way to derive c-structures from f~etructure~.&amp;quot; (\[Block 86\], p.3) I will attempt to clarify this issue in thla paper by 'unf~rbidden' means.</Paragraph>
      <Paragraph position="4"> Sin fact, functional structures are comtonly regarded as equivalence classes ofisomorphlc transition graphs. We can use representatives of these classes wltldn the definitions without lc~s of generality. Furthermove~ all leaves have to labeled by m, if a fmwtional structure is well-formed.</Paragraph>
      <Paragraph position="5"> SThis preflxi~ procedure rune analogously for all other types of constraints, in LFG there are constrMats of the form (v p) =c (P q), (v p), (v p) :c z and their negations (~ mid ~, are node indices, q and p are sequences of attellmtea and z is an atomic value). The safi~factlon relatio~ between DAGs and these types of constraints is usually defined as: C/ ~ (. p) =~ (~ q) ~ 6&amp;quot;(C/.,p) = ~.(C/~,,q) ~ (v p) ~ 8&amp;quot; is defined for (~bv,p) For the negative constraints tim satisfaction relation is defined by the negated conditions. For the sake of brevity, I will refer to only one type in the following, whenever constraints are invdved.</Paragraph>
      <Paragraph position="6"> 1degThe relation that is specified by the Wrg-condition between terminal strings and DAGs is equal to AC/. Both procedures are equivalent, since the order which is given by the respective sequence of applications of rules is imposed onto the fds-algorithin, which otherwise is orderfroe.</Paragraph>
      <Paragraph position="7"> lllt should be noted that these conditions are different from the conditions that an f-structure must be complete and coherent. To avoid confusion the latter ones are called f.eomplete and \]-coher~nt in the following.</Paragraph>
      <Paragraph position="8"> lathe completeness constraints can be nmde explicit by the path set (COMPs:, existential constraints} and the elements of the irrefiezlve subset of the Nerode relation over the path set (COMPb., reentrancy constraints), cf. \[Hesper/Rounds 86\] and \[Kasper 87\]. 13 The purpose of the +-labels will be explained below.</Paragraph>
      <Paragraph position="9"> 14 Tills presupposes that the unification operation preserves labels, but this was already the case for the atomic values.</Paragraph>
      <Paragraph position="10"> 15 Within the actual implementation the eohe~nce condition can be weakened. Atomic-valued features can be selected which are excluded from the coherence check and tlnm can be added during the generation process. Again, it has to be determined in a language specific way which features are entirely predictable either front grarmnatical rules (e.g. strllctural case in German, which under a speclfc analysis could be covered by a structural rule associating nolninative with SUBJ and accusative with 0B J) or front the lexical entries associated with certain predicates (e.g. grammatical gender in German which has to be specified for every noun).</Paragraph>
      <Paragraph position="11">  categorial grammars (UCG) cf. \[Zeevat/Klein/Calder 87\].</Paragraph>
      <Paragraph position="12"> lOThe extension of a syntactic theory by a semantic theol T is called creative iff there are grammars where not all grammatically well-formed sentences are also semautically well-formed; otherwise the exteamion is called conservativv.</Paragraph>
      <Paragraph position="13"> 20 Within a machine translation system this dropping of constraints could be controlled in such a way that a maximal similarity with respect to the stylistic feahtres of the f-structure of the source language sentence has to he ensured. What 'maximal similarity with respect to the stylistic features' mezms again presupposes some empirical work. al One possible additional condition would be to require that each c-structure constituent must be interpreted within the semantic structure, i.e. each c-structure node must be mapped by ~o a (the product) into the semantic structure. Since we wanted to fornminte the algorithm as general as possible, we dispense with this conditiou. 22Since it is possible to express constraints refering to the mapping a between * and )~ (inter-modular constraints, for exaanple), the refere~ce to &amp;, ~ and ~ is necessary.~ 23&amp;quot;1&amp;quot;o separate the f- and a-st~atcture from eadx other wc only have to eliminate the a-transitions.</Paragraph>
      <Paragraph position="14"> alThe semantic fimction of a gramnmtical function is identified with the semantic attribute, whose value COlTesponds to the a-value of that grannnatical fnnction.</Paragraph>
    </Section>
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