Translation Divergence

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Translation Divergence

• LING 580MT
• Fei Xia
• 1/10/06

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Papers

• Bonnie Dorr (1994) Machine Translation
  Divergences a Formal Description and Proposed
  Solution

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Outline

• Formal definition of translation divergence
• Seven types of divergence
• Discussion
• Remaining questions

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Formal definition of translation divergence
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Distinction between the source and target
languages

• Two categories (Bernett et. al., 1991)
• Translation divergence same information,
  different structures
• Translation mismatches different information ?
  important, but outside of the scope of the paper

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How to define translation divergence formally?

• Define the language-to-language divergence via
  language-to-interlingua divergence
• Interlingua lexical conceptual structure (LCS)
• Language-to-interlingua mapping from syntactic
  form to LCS

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Lexical conceptual structure (LCS)
X T(X)
W T(W)
Z1 T(Z1)
Zn T(Zn)
Qm T(Qm)
Q1 T(Q1)


X logical head W logical
subject Z1Zn logical argument Q1Qm
logical modifiers T(F) is the logical type
(Event, Path, .) of the primitive F (CAUSE,
LET, GO, )
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Root LCS (RLCS)

• A RLCS is an un-instantiated LCS that is
  associated with a word definition in the lexicon
  (i.e., a LCS with unfilled variable position)
• LCSs are recursively defined.

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RLCS representation for go
GOLoc Event
X Thing
TOLoc Path
ATLoc Position
X Thing
Z Location
? It is different from dependency structure
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Composed LCS (CLCS)

• A CLCS is an instantiated LCS that is the result
  of combining two or more RLCSs by means of
  unification (roughly).
• This is the interlingua form that serves as the
  pivot between the source and target languages.

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CLCS representation for John went happily to
school
GOLoc Event
John Thing
TOLoc Path
Happily Manner
ATLoc Position
School Location
John Thing
?The operations of combining are not defined in
this paper.
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Syntactic phrase
X syntactic head W external argument Z-MAX
i internal arguments Q-MAXi syntactic adjuncts
? Similar to X-bar theory, GB theory, etc.
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An example
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Mapping between LCS and syntactic form

• Generalized linking routine (GLR)
• X ? X (logical head ? syntactic head)
• W ? W (logical subject ? external
  argument)
• Z ? Z (logical argument ? internal
  argument)
• Q ? Q (logical modifiers ? syntactic
  adjunct)
• Canonical syntactic realization (CSR)
• Relate T(F) to CAT(F) (logical type ? syntactic
  category)
• Ex THING ?N, EVENT ? V

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Divergence problem

• Translation divergences occur when there is an
  exception either to the GLR or to the CSR (or to
  both) in one language, but not in the other.

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Outline

• Formal definition of translation divergence
• Seven types of divergence
• Discussion
• Remaining questions

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T1 Thematic divergence

• The repositioning of arguments w.r.t. a head.
• GLR W ?Z and Z?W
• Example

I like Mary ? Maria me gusta
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INT and EXT
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General Solution
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T2 Promotional Divergence

• Promoting a logical modifier into a main verb
  position (or vice versa)
• GLR X?Z and Q?X
• Ex

John usually goes home ? Juan suele ir a casa
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PROMOTE
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General Solution
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T3 Demotional Divergence

• Demoting a logical head into an internal argument
  (adjunct?) position (or vice versa).
• GLR X?Q and Z?X
• Ex I like to eat ?Ich gern esse

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DEMOTE
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General Solution
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T4 Structural divergence

• It does not alter the positions used in GLR
  mapping
• But it changes the nature of the relation between
  different positions (i.e., the ?
  correspondence)
• Ex John entered the house ?Juan entro en la casa

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marker
Marker forces logical constituents to be realized
compositionally at different levels
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General solution
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T5 Conflational Divergence

• The suppression of a CLCS constituent (or the
  inverse of the process)
• GLR ? correspondence of step (3) or (4) is
  changed.

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Example
I stabbed John ? Yo le di punaladas a Juan
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CONFLATED
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General solution
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T6 Categorical divergence

• CAT(F) is different from CSR(T(F)).
• Ex I am hungry ? Ich hunger habe

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CAT
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General solution
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T7 Lexical divergence

• As a side effect of other divergences.
• Ex John broke into the room ? Juan forzo la
  entrada al cuarto

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Summary of seven types

• Repositioning (GLR mappings) thematic,
  promotional, demotional divergences
• Changing ? correspondence structural,
  conflational divergences
• Category categorical divergence
• ?? Lexical divergence

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Discussion
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Discussion

• Limits on Repositioning Divergences
• Promotional vs. Demotional Divergences
• Lexical Selection Full Coverage Constraint
• Interacting Divergence Types

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Limits on Repositioning divergences

• Three types to cover all repositioning
  divergences
• Thematic W?Z, Z?W
• Promotional X?Z, Q?X
• Demotional X?Q, Z?X
• (X, W, Z, Q) ? (X, W, Z, Q)
• W has a special status 44256 ? 3327
• a CLCS must contain exactly one head 3327?12

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Limits on Repositioning Divergences (cont)

• Z can never be associated with Q, and Q can
  never be associated with Z 12 ?5
• Modifying relation cannot be reversed 5?4 (Q?X,
  X?Q, Z?Z)
• Argument relation cannot be reversed 4 ?3 (Z?X,
  X?Z, Q?Q)
• Canonical positions 3 ? 2

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Promotional vs. Demotional Divergences

• Promotion is triggered by a main verb (e.g.,
  soler in soler-usually)
• Demotion is triggered by an adverb (e.g., gern in
  like-gern)

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Interacting Divergence Types

• Promotional and thematic divergence
• S Leer libros le suele gustar a Juan
• reading books (him) tends to please (to)
  John
• E John usually likes reading books

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Remaining questions
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Remaining questions Interlingua

• How to build RLCS?
• What are logical head, subject, arguments and
  modifiers? Ex like ? likingly
• How to represent a verb stab ? CAUSE GOPoss
  KNIFE-WOUND
• How are RLCSs combined to form CLCSs?
• Unification substitution?
• Are CLCSs really sufficient to handle all the
  languages?

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Remaining issues divergences

• Are the seven types really sufficient to cover
  all the convergences?
• Is the proof for limits on repositioning
  divergences convincing?
• Translation divergences occur when there is an
  exception to GLR/CSR in one language, but not the
  other what if there are exceptions in both
  languages?
• Can a dependent of X become a dependent of Y?

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Remaining issues MT

• How to build a real MT system with this approach?