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<Paper uid="C88-1053">
  <Title>CI%X T~'EI~ : a translation: syst~ fo~' agricultural market ~epo~:'t s</Title>
  <Section position="3" start_page="262" end_page="265" type="metho">
    <SectionTitle>
3. ~Ilae lexicon
</SectionTitle>
    <Paragraph position="0"> CRITI'ER's lexical component is made up of a basic dictionary of morpho-syntactie lexieal units; a rule component which extends the morpho-syntactic dietionmy; and a dictionea'y of semantic-level units.</Paragraph>
    <Paragraph position="1"> 3,1 The morgho-syntacfic dietionm-y This dictionary lists lexical items in citation form and assigns them morphological and syntactic properties. It is also resptmsible for effecthlg the trmpping of these lexical milts onto the semanfiedevel units, whose properties are described iu a sepm~ate dictionary. Moq,hological p;operties include an inflectional class and an indication of any morpho-.synctactic idiosyncrasies.</Paragraph>
    <Paragraph position="2"> Syntactic W~Perties ~tft~ etnN~rised of a subcategorizationfra~tw mid a collection of syntactic feattu'es. The subcategorization frame of a lexical head describes the number and syntactic type of the phrases governed by that headdeg These fiames refer directly to positions in serrate s~ructm'e~ sim;c this is the only level of syntactic representation admitted in our systenL Vcrbs, for example, can he nlarked fbr a maximum of three positions: a subject and up to two eo/nplemeilt:;.</Paragraph>
    <Paragraph position="3"> The mapping onto sematltic units is effected by associating each lexi(:a) ~mtry wilh a semantic schema. This schema is made up ~J a semantic refit (represented as a \[imcto:\[' with a fixed arity), and a~ i~Micatio~ of the ~elatiom;hip of the arguments to lhe lexica\] unit's syntae,i(: dependents.</Paragraph>
    <Paragraph position="4"> hi each lcxical cnhy, this complex of morphological, syatactie md setnantie :infi)rmation is specified as a feature sttuettue. 'it'~fis feature st~uetmg is cucoded as a Prolog term that wc deserxbe indirectly, by means of predicates which access the relevam athibute values. For example, the syntactic and semantic properties el the verb 'promise' coukt be represented as a term T, described as \[bllows:</Paragraph>
    <Paragraph position="6"> eitat,on .tbnn(T, promise), subcat(T, \[NPI, NP2, VCOMP\]), cat(NPl, up), sere form(NPl, A), cat(N P.2, up), sere fonn(NP2, B)~ cat(VCOMP, vp)0 vfo~:J n(VCOMP, infinitive), sere .folm(VCOMP, C), con|yol(VCOMP, NPI)~ sere..term(T, promise'(A~ B, C))  The predicates citadon form, ca6subcat and sem form simply acce:;:; the value of an attribute of the same name in the term T. The subc:q attribute h~Ls a value of the list type, as i~, &lt;Poll,'u'd &amp; Sag (1988):~ Syntactic ~ules will unify the elements of this list with the complements of the lexical head, thereby entbrcing the appropriate ~uhcategorization restrictions (e.g. the &amp;quot;cat&amp;quot; of the sceond complement of 'promise' is vp).</Paragraph>
    <Paragraph position="7"> '\['ak~ n together the subcat and sen(form attributes account fi)r an essential part of the syntax/semantics mapping. According to the description given for 'pronrise', the semantic objects associated with the sut~iect, the object and the infinitival complement are respectively mapped onto the first, second and third argument of the semantic predicate promise'.</Paragraph>
    <Paragraph position="8"> All Ihe resources of clausal logic can be invoked to enforce complex relationships between sevenfl feature structures. For example, the predicate conCrol used in (3.a) above is defined in such a way a'.; to ensur~ that the sere. jbrm and agree values of the controller mttch those of the subject slot in the subcat of the  .~mbject of 'p~omise' and the understood subject of its infinitival eomt)lemcnt me the same ~ntity.</Paragraph>
    <Section position="1" start_page="262" end_page="265" type="sub_section">
      <SectionTitle>
3.2 Morphological and lexical roles
</SectionTitle>
      <Paragraph position="0"> The rnorpho-syntactie dictionary is extended by three sets of rules that handle inflection, derivation and lexical transformations. Our description of French inflection is based on the work of Bourheau &amp; Pinard (1986), which provides an exhaustive speeifieation of the inflectional properties of more than 50,000 French lexieal items. We have also developed a parallel description for English inflection.</Paragraph>
      <Paragraph position="1"> We currently employ a rule-based treatment of derivafional morphology only for the most productive classes, such as comparative and superlative adjectives, '-ly' adverbs, etc. On the other hand, we make extensive use of lexieal transformations to handle phenomena such as passivization, subject-to-subject and subject-to~object raising, intransitivation, dative-shift, etc. Given the scheme described above for lexical subcategorization, most lexical transformations can be seen as simply altering the subcategorization pattern of the lexical entry.</Paragraph>
      <Paragraph position="2"> For example, given the lexical specification (3.c) for the object-raising verb 'believe', ride (3.d) has the effect of generating the two &amp;quot;virtual&amp;quot; dictionm3r entries (3.e) and (3.0.</Paragraph>
      <Paragraph position="4"> sere form(NP, A), eat(S, sbar), complementizer(S, that), sere form(S, B), sern .form(T, believe(A,B)). &amp;quot;Tom believes that Bill is dishonest.&amp;quot; citation_form(T, believe), subcat(T, \[NP1, NP2, VCOMP\]), eat(NPl, up), sere fonn(NP 1, A), cat(NP2, up), sem_form(VCOMP, B), eat(VCOMP, vp), form(VCOMP, infinitive), eoutrol(VCOMP, NP2), sere form(T, believe(A,B)). &amp;quot;Tom believes Bill to be dishonest.&amp;quot;</Paragraph>
    </Section>
    <Section position="2" start_page="265" end_page="265" type="sub_section">
      <SectionTitle>
3.3 The semantic lexicon
</SectionTitle>
      <Paragraph position="0"> The semantic lexicon defines a set of semantic units for each language (whether directly realized by a lexeme or more abstract); describes a subsumption hierarchy of semantic types ( a partial order of types &lt;Sowa, 1983&gt;); and associates with each semantic unit SU an initial semantic type, this having the consequence that SU belongs implicitly to all higher types in the hierarchy. The semantic lexicon also defines a set of validating predicate-argument schemas, of which valid predicate-argument structures have to be instances. An example of such a schema is: MOVEMENT( MEASURE-FUNCTION, INCREMENT, MEASURE) where MOVEMENT, MEASURE-FUNCTION, INCREMENT and MEASURE are semantic types.</Paragraph>
      <Paragraph position="1"> The use of the semantic lexicon to test semantic structure well-formedness is briefly explained in section 4.3.</Paragraph>
    </Section>
  </Section>
  <Section position="4" start_page="265" end_page="265" type="metho">
    <SectionTitle>
4. The Grammars
</SectionTitle>
    <Paragraph position="0"/>
    <Section position="1" start_page="265" end_page="265" type="sub_section">
      <SectionTitle>
4.1 Syntactic Rules
</SectionTitle>
      <Paragraph position="0"> CRITTER's grammars assign textual units a feature structure describing both their syntactic form and semantic content. As an example, consider rule (4.a):</Paragraph>
      <Paragraph position="2"> subcat(VB, \[SUJ, CO1, CO2\]), head of(VBAR, VB)}..</Paragraph>
      <Paragraph position="3"> The constituent vbar is expanded as a verb and two possible complements.</Paragraph>
      <Paragraph position="4"> Generally speaking, a complement can be any of a wide range of phrases:</Paragraph>
      <Paragraph position="6"> Most of the syntactic rules that we use are, like (4.a), based on the simple context-free skeleton of definite clause grammars, with the same augmentation mechanisms: non-terminals have arguments and additional PROLOG goals (enclosed in braces) can be stated. The non-terminals in our rules are uniformly assigned a single argument, whose content is a feature structure, and the PROLOG goals are used to state mutual constraints between these feature structures.</Paragraph>
      <Paragraph position="7"> In example (4.a), the two complements of the verb are unified with the second and third elements of the subcat list of the verb, thereby enforcing its lexical subcategorization requirements. The head_of predicate is defined so as to unify the head features of' the lexical head with those of the larger verb phrase. Since sem_form is a head feature, the lexical value of sem_form for the verb will be assigned to the verb phrase. In the process, arguments of the semantic predicate associated with the verb will become instantiated to the semantic objects associated with the complements of the verb.</Paragraph>
      <Paragraph position="8"> In older to deal with certain more complex syntactic phenomena, such as unbounded dependencies, we take advantage of the special facilities built into the extraposition grammar formalism.</Paragraph>
    </Section>
    <Section position="2" start_page="265" end_page="265" type="sub_section">
      <SectionTitle>
4.2 Syntactic processing
</SectionTitle>
      <Paragraph position="0"> Although the format of our grammatical rules closely resembles the format of definite clause grammars (DCGs) and extraposition grammars (XGs), there are some important differences.</Paragraph>
      <Paragraph position="1"> Because of their direct relationship with clausal logic, DCGs and XGs have two distinct interpretations: on the one hand, a declarative interpretation in which they can be viewed as defining a relation between strings and structural descriptions; and on the other hand, a procedural interpretation in which they may be viewed indifferently as parsers or synthesizers.</Paragraph>
      <Paragraph position="2"> However, given the standard compilers for these formalisms, the procedural interpretation of any given set of rules can rarely be used for both analysis and synthesis tasks. For example, any DCG contaiuing:left-recursive rules will produce infinite loops when applied to analysis tasks, although the same grammar may well be suitable for synthesis tasks. Moreover, in order to obtain reasonably efficient parsers and synthesizers, it is necessary to control the order in which goals are called in each mode.</Paragraph>
      <Paragraph position="3"> Our solution to these problems is to retain the use of DCGlike rules which have a well-defined declarative semantics; however, we enrich these rules with control annotations which, while not affecting their semantics, provide a rule compiler with the information needed to produce both an analysis-oriented and a synthesis-oriented version of the rule. Left-recursion is elinfinated in the analysis version, and both versions typically display a different ordering of the goals. The result is that we can actually derive fairly efficient parsers and synthesizers from one and the same grammar.</Paragraph>
      <Paragraph position="4"> For furtber details on this double-compilation approach, see Dymetman &amp; Isabelle (1988).</Paragraph>
      <Paragraph position="5"> ~.3 Checking of semantic well-formedness In order for a semantic structure built by this compositional process to be accepted as valid, it must pass a semantic well-formedness check, which involves semantic constraints and the type subsumption hierarchy.</Paragraph>
      <Paragraph position="6"> This check can be briefly described as follows: for each predicative (or functional) node pn in the semantie structure, having an1, an2.., as argument nodes, one tries to find a validating schema (see SS3.3) PT(AT1,AT2,....) such that PT is a type subsuming pn, AT1 a type subsuming anl, AT2 a type subsuming an2 ....</Paragraph>
      <Paragraph position="7"> For instance, given the semantic slracttne of section 2.2~ partially annotating it with the types of each node yields (4.c).</Paragraph>
    </Section>
  </Section>
  <Section position="5" start_page="265" end_page="265" type="metho">
    <SectionTitle>
5. Transfer
</SectionTitle>
    <Paragraph position="0"> As we have seen, the transfer component implements a relation between two language-dependent semantic structures. The decision to restrict the input and output of transfer to such semantic structures is motivated by a number of considerations. Pretheoretically, the very notion of translation implies a linguistic reformulati(m which preserves essential meaning. Such abstract intermediate structures also have the practical advantage of simplifying the transfer component. That is to say, we assume that the analysis component is powerful enough to neutralize certain source language transformations and that a full-fledged synthesis component can take care of such details of target language realization ~ governed prepositions.</Paragraph>
    <Paragraph position="1"> The transfer component itself is essentially lexieal, with all relevant knowledge expressed in a transfer lexicon, a sample of which appears in (5.a) : (5.a) (i) eat &lt;-&gt; manger.</Paragraph>
    <Paragraph position="2"> (ii) miss( 1: X, 2: Y ) &lt;-&gt; manque*'( 1: Y', 2: X' ).</Paragraph>
    <Paragraph position="3"> (iii) walk( inv-l: acress( 2: X ) ) &lt;-&gt; traverser( 2: X', inv-l: $manner (2: apied) ).</Paragraph>
    <Paragraph position="4"> entry (i) is straightforward; entry 0i) expresses an &amp;quot;argument conversion&amp;quot; : john misses mary &lt;=&gt; mary manque d john; entry (iai) expresse s a more complex corresl~ondanee: john walks across the str, n:t &lt;=&gt; john traverse la rue d pied This lexicon is compiled into a set of Prolog clauses. The transfer algorithm then performs a simultaneous reeursive root-to-leaves travta'sal of source and target semantic structures, making use of these clauses to maintain translational equivalence of the source and target structures. Practically speaking, the result is that when translating from English to French, for example, as the transfer algorithm traverses the English semantie structure, the Freneh semantic structure is constructed in parallel, by progressive instontiations.</Paragraph>
    <Paragraph position="5"> In this way, the transfer process may effect certain restructurings, but these are lexically triggered: we do not foresee the need for an independent structural transfer component, as in ARIANE-78 for example &lt;c.f. Boitet &amp; Nedobejkine, 1981&gt;.</Paragraph>
  </Section>
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