<?xml version="1.0" standalone="yes"?>
<Paper uid="P98-1056">
  <Title>Syntactic and Semantic Transfer with F-Structures*</Title>
  <Section position="3" start_page="341" end_page="342" type="metho">
    <SectionTitle>
2 Syntactic Transfer
</SectionTitle>
    <Paragraph position="0"> This section presents a simple bidirectional translation between LFG f-structures and term representations which serve as input to and output of a transfer component developed within the Verbmobil project (Dorna and Emele, 1996a). The term representation is inspired by earlier work (Kay et al., 1994; Caspari and Schmid, 1994) which uses terms as a quasisemantic representation for transfer and generation. null The translation between f-structures and terms is based on the correspondence between directed graphs representing f-structures and the functional interpretation of these graphs (cf. (Johnson, 1991)). Given an arc labeled f which connects two nodes nl and n2 in a graph, the same can be expressed by a function f(nl) = n2. An f-structure is the set of such feature equations describing the associated graph. Instead of feature equations f(nl) -- n2 we use the relational notation f(nl, n2).</Paragraph>
    <Paragraph position="1"> Using this idea f-structures can be converted into sets of terms and vice versa} F-structure 1For motivation why we prefer term representations PRED features and their &amp;quot;semantic form&amp;quot; values are given special treatment. Instead of introducing PRED terms we build unary relations with the semantic form predicate name as functor (see Example (1)). The resulting representation is similar to a Neo-Davidsonian style event semantics (Parsons, 1991) but uses syntactic roles. For a formalization of the f-structure-term cor- null respondence see Appendix A.</Paragraph>
    <Paragraph position="2"> l (I) a. /PRED ~o~.~,,(~SUBJ) /m LADJN { \[PRED GERNE\]\[~\]} J b. Hans kocht gerne C. { kochen(nl), SUBJ (nl ,n2), Hans (n2), ADJN(nl,n3), gerne(n3) }  Consider the simple head switching example involving the German attitude adverb gerne and the English verb like (see (lb) and (3b)). (la) is the LFG f-structure for the German sentence (lb). 2 (lc) is the set of terms representing (la).</Paragraph>
    <Paragraph position="3"> Transfer works on source language (SL) and target language (TL) sets of terms representing predicates, roles, etc. like the ones shown in (lc). The mapping is encoded in transfer rules as in (2). For a rule to be applied, the set on the SL side must be a matching subset of the SL input set. If this is the case, we remove the covering set from the input and add the set on the other side of the rule to the TL output. Transfer is complete, if the SL set is empty.</Paragraph>
    <Paragraph position="4">  (2) a. &amp;quot;\[ kochen(E) \]&amp;quot; &lt;-&gt; { cook(E) }.</Paragraph>
    <Paragraph position="6"> The transfer operator &lt;-&gt; is bidirectional. Upper case letters in argument positions are logical variables which will be bound to nodes at runtime. Because of the variable sharings on both sides of a rule we work on the same nodes of a graph. The result is a graph rewriting process.</Paragraph>
    <Paragraph position="7"> over feature structures for transfer, see (Emele and Dorna, 1998).</Paragraph>
    <Paragraph position="8">  The head switching rule (2d) shows two components on its lefthand side: the part to the right of # is a test on a copy of the original input. The test binds the variable Y at runtime when applying the rule from left to right. In the reverse direction (and in general), TL tests are ignored. Applying the rule set in (2) to (lc), we get (3c). We now use the correspondence between f-structures and term representations to construct the TL f-structure. The result is (3a) represent- null ing the English sentence (3b).</Paragraph>
    <Paragraph position="9"> &amp;quot;suBJ \[PRED \] PRED LIKE(~ SUB J, I&amp;quot; XCOMP) /(3) a. \[SUBJ \[PRED HANS\]I~I\]~/131 XCOMe \[PRED ooo ( SUB.&gt; jwj b. Hans likes cooking</Paragraph>
    <Paragraph position="11"/>
  </Section>
  <Section position="4" start_page="342" end_page="343" type="metho">
    <SectionTitle>
3 Semantic Transfer
</SectionTitle>
    <Paragraph position="0"> Semantic-based transfer as detailed in (Dorna and Emele, 1996a; Dorna and Emele, 1996b) is based on rewriting underspecified semantic representations. The representations (Bos et al., 1996) are UDRS variants (Reyle, 1993).</Paragraph>
    <Paragraph position="1"> F-structures are abstract syntactic representations. They do, however, encode basic predicate-argument relations, and this is essentially semantic information. It turns out that there are important structural similarities between f-structures and UDRSs: f-structures can be &amp;quot;read&amp;quot; as UDRSs and hence be assigned an underspecified truth-conditional interpretation (Genabith and Crouch, 1997). 3 Appendix B gives a relational formulation of the correspondence between f-structures and UDRSs.</Paragraph>
    <Paragraph position="2"> The UDRS representations are processed by semantic-based transfer. The resulting system is bi-directional. Consider again the simple head switching case discussed in (1) and (3) above.</Paragraph>
    <Paragraph position="3"> (4) shows the corresponding UDRSs.</Paragraph>
    <Paragraph position="4"> The structural mismatch between the two f-structures has disappeared on the level of UDRS representations and transfer is facilitated. 4</Paragraph>
    <Paragraph position="6"/>
    <Section position="1" start_page="342" end_page="342" type="sub_section">
      <SectionTitle>
Multiple Adjuncts
</SectionTitle>
      <Paragraph position="0"> How do the two approaches fare with embedded head switching and multiple adjuncts? Due to space limits we will not discuss straightforward cases where ambiguites represented in underspecified representations are carried over into the target language. Examples of this type involve quantificational and plural NPs, negation, or adjunct sets. Instead, we concentrate on complex cases where a source language ambiguity needs to be resolved in target language.</Paragraph>
    </Section>
    <Section position="2" start_page="342" end_page="343" type="sub_section">
      <SectionTitle>
4.1 Embedded Head-Switching
</SectionTitle>
      <Paragraph position="0"> The syntactic transfer rules (2) are supplemented by (5). The complex rule for gerne in (5) overrides 5 (2d) and the COMP rule in (5). For each additional level of embedding triggered by head switching adjuncts a special rule is needed.</Paragraph>
      <Paragraph position="2"> By contrast, on the level of UDRSs head switching has disappeared and transfer is facilitated.</Paragraph>
      <Paragraph position="3"> Figure 1 shows the transfer correspondence between terms and UDRSs.</Paragraph>
      <Paragraph position="4"> coding of predicate argument relations is used. The sub-ject of the target like relation is determined by the following transfer rule:</Paragraph>
      <Paragraph position="6"> _~ is the transitive closure over subordination constraints &lt;. Here and in the following we do not give set representations of UDRSs and transfer rules. Instead, we provide a graphical representations of standard UDRSs to better illustrate the structural mismatches discussion.</Paragraph>
      <Paragraph position="8"/>
    </Section>
    <Section position="3" start_page="343" end_page="343" type="sub_section">
      <SectionTitle>
4.2 Multiple Adjuncts
</SectionTitle>
      <Paragraph position="0"> Consider the sentences in (6).</Paragraph>
      <Paragraph position="1">  (6) a. Oft kocht Hans gerne b. Hans kocht gerne oft c. Often Hans likes cooking d. Hans likes cooking often (6a) is ambiguous between (6c) and (6d), (6b) can only mean (6d). (6c) and (6d) are not ambiguous. (6a) is represented by f-structure (7a). &amp;quot;SUBJ \[PRED HANS\]~\] }\] (7) a. PRED }&lt;OCHEN&lt;~&amp;quot; SUB J&gt;</Paragraph>
    </Section>
  </Section>
  <Section position="5" start_page="343" end_page="344" type="metho">
    <SectionTitle>
\[PRED OFT\]\[~\] \[\]
ADJN \[PRED OE.NE \] \['4\]
</SectionTitle>
    <Paragraph position="0"/>
    <Paragraph position="2"> The corresponding term representation is (7b) and, in the absence of further constraints, we get a flat scopally underspecified UDRS (7c). Let (6a) be our translation candidate. For syntactic transfer, adding rules (9) to the ones introduced in (2) leads to (8a).</Paragraph>
    <Paragraph position="4"/>
    <Paragraph position="6"> (8a) corresponds to only one of the English translations, namely (6d), of (6a). As in the correspondence-based approach (Haplan et al., 1989), often can only be assigned wide scope over like if the transfer formalism allows reference to and rewriting of partial nodes. In the present case the two terms kochen(nl). SUBJ(nl,n2) could then be rewritten as the complement of like, XCOMP(n4,nl), whereas ADJN(nl,n3) is rewritten as ADJN(n4,n3) or hDJN(nl ,n3).6 The target f-structure for English must resolve the relative scope between like and often ((8b) and (10)).</Paragraph>
  </Section>
  <Section position="6" start_page="344" end_page="344" type="metho">
    <SectionTitle>
.ADJN {\[PRED OFTEN\]\[~\]} J
</SectionTitle>
    <Paragraph position="0"> Semantic transfer on the source UDRS (7c) preserves the underspecification and leads to (11).</Paragraph>
    <Paragraph position="2"> However, (11) is not in the direct f-structure UDRS correspondence with (10) and (Sb). Instead, the correspondences on the enumerations of the scoping possibilities of (11) yield (10) and (8b) as required.</Paragraph>
    <Paragraph position="3"> By contrast, the reading of (6b) is restricted by the surface order in which the two adverbials occur. On the semantic level this is reflected in terms of corresponding subordination constraints (12). The target UDRS corresponds to f-structure (Sb).</Paragraph>
    <Paragraph position="4"> OAs an alternative, we can get both readings if we define special rules for adverbials in head switching contexts, giving them wide or narrow scope relative to the head switching adverbial. A narrow scope rule is already given in (9). A wide scope rule would be {hDJN(E,X)} # {HS(E1), XC0~IP(E1,E)} ~-} {ADJN(EI,X)} where HS(E1) is a &amp;quot;marker&amp;quot; on the switched adverbial's node El.</Paragraph>
    <Paragraph position="6"> l\[~: I gerne(l~ 1 ) I l\[~: I like(x~, 1~1) I</Paragraph>
    <Paragraph position="8"> In LFG linearization effects can be captured in terms of f-precedence constraints 41 as in (13).</Paragraph>
    <Paragraph position="9"> Semantic subordination and f-precedence constraints can then be linked as in (14).</Paragraph>
    <Paragraph position="10"> (14) \[~ -&lt;$ \[\] ~ ~ l~ _&lt; l\[il 1 With (14) the head switching - multiple adjunct interaction is correctly resolved in semantic-based transfer. Similarly, in syntactic transfer, the precedence constraint (13) can be used to steer translation to f-structure (8b).</Paragraph>
  </Section>
class="xml-element"></Paper>