1 Introduction LING 572 Fei Xia, Dan Jinguji Week 1: 1/08/08.
Translation Divergence LING 580MT Fei Xia 1/10/06.
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Transcript of Translation Divergence LING 580MT Fei Xia 1/10/06.
Translation Divergence
LING 580MT
Fei Xia
1/10/06
Papers
• Bonnie Dorr (1994): Machine Translation Divergences: a Formal Description and Proposed Solution
Outline
• Formal definition of translation divergence
• Seven types of divergence
• Discussion
• Remaining questions
Formal definition of translation divergence
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
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
Lexical conceptual structure (LCS)
])]]...[[]]...[[],'(['[ '
)(
'1)(
'
)(
'1)()'()'( ''
1''
1mQTQTnZTZTWTXT QQZZWX
mn
X’T(X’)
W’T(W’)
Z1’T(Z1’)
Zn’T(Zn’)
Qm’T(Qm’)
Q1’T(Q1’)
X’: logical head W’: logical subjectZ1’…Zn’: logical argument Q1’…Qm’: logical modifiersT(Φ’) is the logical type (Event, Path, ….) of the primitive Φ’ (CAUSE, LET, GO, …)
… …
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.
RLCS representation for go
XThing
TOLoc
Path
ATLoc
Position
XThing
ZLocation
GOLoc
Event
It is different from dependency structure
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.
CLCS representation for “John went happily to school”
JohnThing
TOLoc
Path
ATLoc
Position
JohnThing
SchoolLocation
GOLoc
Event
HappilyManner
The operations of combining are not defined in this paper.
Syntactic phrase
X: syntactic head W: external argumentZ-MAX i: internal arguments Q-MAXi: syntactic adjuncts
Similar to X-bar theory, GB theory, etc.
An example
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(Φ’) to CAT(Φ): (logical type syntactic
category)
Ex: THING N, EVENT V
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.
Outline
• Formal definition of translation divergence
• Seven types of divergence
• Discussion
• Remaining questions
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
:INT and :EXT
General Solution
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
:PROMOTE
General Solution
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
:DEMOTE
General Solution
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
* marker
Marker forces logical constituents to be realized compositionally at different levels
General solution
T5: Conflational Divergence
• The suppression of a CLCS constituent (or the inverse of the process)
• GLR: correspondence of step (3) or (4) is changed.
ExampleI stabbed John Yo le di punaladas a Juan
:CONFLATED
General solution
T6: Categorical divergence
• CAT(Φ) is different from CSR(T(Φ’)).• Ex: I am hungry Ich hunger habe
:CAT
General solution
T7: Lexical divergence• As a side effect of other divergences.• Ex: John broke into the room Juan forzo la entrada al cuarto
Summary of seven types
• Repositioning (GLR mappings): thematic, promotional, demotional divergences
• Changing correspondence: structural, conflational divergences
• Category: categorical divergence
• ??: Lexical divergence
Discussion
Discussion
• Limits on Repositioning Divergences
• Promotional vs. Demotional Divergences
• Lexical Selection: Full Coverage Constraint
• Interacting Divergence Types
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: 44=256 33=27– a CLCS must contain exactly one head:
33=2712
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: 54 (Q’X, X’Q, Z’Z)
• Argument relation cannot be reversed: 4 3 (Z’X, X’Z, Q’Q)
• Canonical positions: 3 2
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)
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
Remaining questions
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?
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?
Remaining issues: MT
• How to build a real MT system with this approach?