Xerox Research Centre Europe 26/11/1998 LFG-based syntactic transfer from English to French with XTE The Xerox Translation Environment

Xerox Research Centre Europe26/11/1998

LFG-based syntactic transfer from English to French

with XTE The Xerox Translation Environment


The Translation Architecture Source and Target LFG Grammars

Some Examples from the Corpus Transfer Coverage

Rule Ordering in a Transfer GrammarExamples of “stepwise” Transfer: Nominalization and Coordination

More on Coordination:Structure Deletion and Root Node Rewriting

Translation Cycles and Optional Rules

Overview


The Translation Architecture Source and Target LFG Grammars


The XTE Xerox Translation Environment

Translation Architecture

SL f-structure

SL f-structure terms

Source language string

XLE parsing

XTE term rewriting system

Transfer rulesTL f-structureterms

underspecified TL f-structure

Target language strings

XLE generation

disambiguation

pred(f,walk)subj(f,g), pred(g,’John’)

pred(A,walk) ==> pred(X,marcher).pred(A,’John’) ==> pred(X,’Jean’).

pred(f,marcher),subj(f,g), pred(g,’Jean’)


The XTE Xerox Translation Environment

Translation Architecture

SL f-structure

SL f-structure terms

Source language string

XLE parsing

XTE term rewriting system

Transfer rulesTL f-structureterms

underspecified TL f-structure

Target language strings

XLE generation

disambiguation

pred(f,walk)subj(f,g), pred(g,’John’)

pred(A,walk) ==> pred(X,marcher).pred(A,’John’) ==> pred(X,’Jean’).

pred(f,marcher),subj(f,g), pred(g,’Jean’)

External AttributesaddonlyInternal Attributes


Source and Target Language LFG Grammars

• Source language grammar: English (Tracy Holloway King - PARC)

• Target language grammar: French (Anette Frank, Veronika Lux - XRCE)

– Special focus on generation from underspecified structures

– Use of ``optimality’’ (preference) marks and surface order constraints to define e.g.

• preferred default positions for adverbs of different types• preferred default positions of adjuncts

– LFG grammars are reversible, but specify different preference rankings for analysis and generation mode


Some Examples from the Corpus Transfer Coverage


To keep your HomeCentre in good operating condition, you need to perform periodic maintenance tasks.Pour assurer le bon fonctionnement du HomeCentre, vous devez effectuer périodiquement des tâches d’entretien.

HEADER: Removing and Replacing the Paper CassetteHEADER: Retrait et mise en place de la cassette papier

Before you add paper, make sure that the paper matches the paper size setting in Windows.Avant d’ajouter du papier, assurez-vous que le papier correspond au format de papier sélectionné.

Keep in mind that you can’t use paper that is wider than 8 inches in the HomeCentre.N’oubliez pas que vous ne pouvez pas utiliser du papier qui dépasse 8 inches dans le HomeCentre.

Fan the paper and put up to 125 sheets into the paper tray.Ventilez le papier et placez jusqu’à 125 feuilles dans le plateau de départ papier.

Make sure that the green carriage lock lever is STILL moved all the way forward before you reinstall the print head.Assurez-vous que le levier vert de verrouillage du chariot est TOUJOURS repoussé complètement vers l’avant avant de remettre la tête d’impression en place.

Some Examples from the Corpus


Transfer Coverage

The transfer corpus: A contiguous section of the HomeCentre user manual -- Chapter 6

(99 sentences/text items)

• A basic transfer “grammar” for translation from English to French

• 545 compiled transfer rules: 171 structural transfer rules 76 lexicalized transfer rule templates (374 instantiated lexical transfer rules; approx. 5 entries per rule template)

• Translations for 94 sentences


Rule Ordering in a Transfer Grammar


Overall Organization of a Transfer Grammar

Deleting grammar specific features of SL grammar Adjusting minor differences between SL and TL f-structures (e.g. create uniform feature space for nominals)General transformations on feature structures adjunct(A,B), in_set(C,B) ==> adjunct_x(A,C).

Lexical and structural transfer rules

nominalizationverbsnounsadjectivesadverbsconjunctionsprepositions

General transformations on feature structures (ADJUNCT)Final adjustments to match TL feature structures

Input

Output


% Simple verbs

restriction/A :: 0 ==> 0.opt :: 0 ?=> 0.

Source -> Target :: % main transfer rule pred(A,Source), +vtype(A,_) ==> pred(A, Target) && opt && restriction/A.

open -> soulever. % optional opt :: 0 ==> 0.

open -> ouvrir. % obligatoryfan -> ventiler.

restriction/A :: -obj(A,_) ==> inhrefl/A. print -> imprimer. % intransitive to intransitive reflexive appear -> afficher.

Defining Optionality and Restrictions


Examples of “stepwise” Transfer:

Nominalization


Nominalization

HEADER: Removing the print head -- Retrait de la tête d’impression


Nominalization

… when moving the printer -- .. lors du déplacement de l’imprimante


nominal_or_verbal/A :: nominal_gerund_features/A, spectype(_)/A ==> spectype(def)/A ; verbal_gerund_features/A ==> spectype(def)/A, ntype(A,_), default_nominal_agr/A.

nominalization(SourceVerb,TargetNoun) :: pred(A,SourceVerb), tns_features/A ?=> pred(A,TargetNoun), nominalized(A) && nominal_or_verbal/A.

nominalization(print, impression).nominalization(move, déplacement).

nominalization(remove, retrait).

“Stepwise” Transfer

Rewriting a verbal head with verbal featuresinto a nominal head with nominal features

First step: The nominalization rule


pred(0,remove)subj(0,1), pred(1,pro), pron_type(1,null)obj(0,2), pred(2,print head), ntype(2,2), grain(2,count), spec(2,4), spec_type(4,def), pers(2,’2’), num(2,sg),tns_asp(0,5), prog(5,+), perf(5,-),passive(0,-), pers(0,’2’), layout_type(0,header), stmt_type(0,header), vtype(0,main), num(0,sg),ntype(0,6), gerund(6,+), type(6,eventive).

pred(A,remove), tns_asp(A,B), perf(B,_), prog(B,_), vtype(A,_), +ntype(A,C), gerund(C,+), type(C,eventive) ?=> pred(A,retrait), nominalized(A).

Applying the nominalization rule to the input


pred(0,retrait), nominalized(0),subj(0,1), pred(1,pro), pron_type(1,null)obj(0,2), pred(2,print head), ntype(2,2), grain(2,count), spec(2,4), spec_type(4,def), pers(2,’2’), num(2,sg),passive(0,-), pers(0,’2’), layout_type(0,header), stmt_type(0,header), num(0,sg),ntype(0,6).


+nominalized(A), passive(A,-) subj(A,B), null_pron/B, obj(A,C) ==> adjunct_x(A,D), prepsem(de)/[D,C].

Second step: Relation changes in nominalization

Case 1: active transitive verbsrewrite transitive object into de-adjunct; delete null subject

Ex: start printing the page again ==> reprenez l’impression de la page


+nominalized(A), passive(A,-), subj(A,B), null_pron/B ==> 0.


Case 2: active intransitivedelete null subject

Ex: start printing again ==> reprenez l’impression


+nominalized(A), passive(A,-), subj(A,B), null_pron/B ==> adjunct_x(A,C), prepsem(de)/[C,B].


Case 3: passiverewrite passive subject into de-adjunct

Ex: when the scanner is being calibrated ==> pendant l’ étalonnage du scanner


pred(0,retrait), nominalized(0), spec(0,7), spec_type(7,def), subj(0,1), pred(1,pro), pron_type(1,null) obj(0,2), pred(2,print head), ntype(2,2), grain(2,count), spec(2,4), spec_type(4,def), pers(2,’2’), num(2,sg), passive(0,-), pers(0,’2’), layout_type(0,header), stmt_type(0,header), num(0,sg), ntype(0,6).

+nominalized(A), passive(A,-) subj(A,B), null_pron/B, obj(A,C) ==> adjunct_x(A,D), prepsem(de)/[D,C].

Applying ``relation changes’’ to the (new) input


pred(0,retrait), nominalized(0),spec(0,7), spec_type(7,def),adjunct_x(0,8), pred(8,de), ptype(8,sem), obj(8,2), pcase(2,de), pred(2,print head), ntype(2,2), grain(2,count), spec(2,4), spec_type(4,def), pers(2,’2’), num(2,sg),pers(0,’2’), layout_type(0,header), stmt_type(0,header), num(0,sg),ntype(0,6).

nominalized(A) ==> 0. pred(A,print head) ==> pred(A,tête d’impression).

Retrait de la tête d’impression


You print a test page when you move the HomeCentre or replace an ink cartridge.Vous imprimez une page de test lorsque vous déplacez le HomeCentre ou (lors)que vous remplacez une cartouche d’encre.

Another Example of “stepwise” Transfer:

Head Switching in Coordination


You print a test page when you move the HomeCentre or replace an ink cartridge.


pred(0,print), subj(0,1), pred(1,pro), pron_type(1,pers), pers(1,’2’), num(1,sg), obj(0,2), pred(2,test page), spec(2,3), spec_type(3,indef), pers(2,’3’), num(2,sg),tns_asp(0,4), tense(4,pres), perf(4,-), prog(4,-),passive(0,-), stmt_type(0,declarative), adjunct_x(0,5), pred(5,when), obj(5,6), conj_level(6,vp), conj_form(6,or), in_set(7,6), pred(7,move), subj(7,8), pred(8,pro), pron_type(8,pers), pers(8,’2’),num(8,sg), obj(7,9), pred(9,HomeCentre), ….. tns_asp(7,10), tense(10,pres), … passive(7,-), stmt_type(7,declarative) in_set(8,6), pred(8,replace), subj(8,9), pred(9,pro), pron_type(9,pers), pers(9,’2’),.. obj(8,10), pred(10,HomeCentre), ….. tns_asp(8,11), tense(11,pres), … passive(8,-), stmt_type(8,declarative).

Source Structure:


Vous imprimez une page de test lorsque vous déplacez le HomeCentre ou (lors)que vous remplacez une cartouche d’encre.


pred(0,imprimer), subj(0,1), pred(1,pro), pron_type(1,pers), pers(1,’2’), num(1,sg), obj(0,2), pred(2,page de test), spec(2,3), spec_type(3,indef), pers(2,’3’), num(2,sg),tns_asp(0,4), tense(4,pres), perf(4,-), passive(0,-), stmt_type(0,declarative), adjunct_x(0,6), conj_level(6,vp), conj_form(6,or), in_set(7,6), pred(7,lorsque), obj(7,8), pred(8,deplacer), subj(8,9), pred(9,pro), pron_type(9,pers), pers(9,’2’), ... obj(8,10), pred(10,HomeCentre), ….. tns_asp(8,11), tense(11,pres), … passive(8,-), stmt_type(8,declarative) in_set(12,6), pred(12,lorsque), obj(12,13), pred(13,remplacer), subj(13,14), pred(14,pro), pron_type(14,pers), ... obj(13,15), pred(15,HomeCentre), ….. tns_asp(13,16), tense(16,pres), … passive(13,-), stmt_type(13,declarative).

Target Structure:


A simple way: Doing it in one step

- rewrite the coordination structure, raise it to the level of the original conjunction (when)- rewrite the conjunction (when) twice as new conjuncts of new coordination structure, - let them embed the original conjuncts (B,C)


semconj(CompForm,AdvType)/[A,Coord], coord(ConjForm)/[Coord,B,C] ==> coord(ConjForm)/[A,Bnew,Cnew], semconj(CompForm,AdvType)/[Bnew,B], semconj(CompForm,AdvType)/[Cnew,C].


A simple way: Doing it in one step

- rewrite the coordination structure, raise it to the level of the original conjunction (when)- rewrite the conjunction (when) twice as new conjuncts of new coordination structure, - let them embed the original conjuncts (B,C)


semconj(CompForm,AdvType)/[A,Coord], coord(ConjForm)/[Coord,B,C] ==> coord(ConjForm)/[A,Bnew,Cnew], semconj(CompForm,AdvType)/[Bnew,B], semconj(CompForm,AdvType)/[Cnew,C].

This rule only accounts for two-conjunct coordination !


“Stepwise” Transfer

semconj(CompForm,AdvType)/[A,Coord], conj_form(Coord,ConjForm) ==> conj_form(A,ConjForm), raise_conjuncts_into_compl(CompForm,AdvType, Coord, A).

+raise_conjuncts_into_compl(CompForm,AdvType, Coord, A), in_set(B,Coord), +subj(B,_) ==> in_set(Bnew,A), semconj(CompForm,AdvType)/[Bnew,B]. raise_conjuncts_into_compl(_,_,_,_) ==> 0.

A better, more general way: Doing it in two steps

- rewrite the coordination structure, raise it to the higher level (A)- delete the conjunction (when) - but transmit the conjunction form and the upper and lower nodes (Coord,A) to the next rule - the next rule creates, for each conjunct (B) of the raised coordination (Coord) a new conjunction (when) that embeds the original conjunct


More on Coordination:

Structure Deletion and Root Node Rewriting


hold Press and release the green LED button.

prolongée Exercez une pression brève sur le voyant vert.





Press and hold the green LED button.Exercez une pression prolongée sur le voyant

vert.

v_coord_v(SourceV1, SourceV2, InterimV) :: conj_form(A,_), in_set(B,A), pred(B,SourceV1), in_set(C,A), pred(C,SourceV2), scopes(B,C) ==> pred(B,InterimV), rewrite(A,B), delete_structure(C).

v_coord_v(press, hold, ’press-hold’).v_coord_v(press, hold, ’press-release’).

First step: structure deletion

rewrite(A,B), { A == var(0) } ==> move_structure(B, var(0)). rewrite(A,B), adjunct_x(X,A) ==> adjunct_x(X,B).

Second step: (root) node rewriting


Press and hold the green LED button.Exercez une pression prolongée sur le voyant

vert.

v v_v_s_o2v_s_obl_o_adj(InterimV, TargetV, TargetSpecType, TargetNoun, TargetAdj, TargetPrep) :: pred(A,InterimV), x_arg/[obj,2,A,B] ==> pred(A,TargetV), x_arg/[obj,2,A,C], pred(C,TargetNoun), spectype(TargetSpecType)/C, ntype(C,_), default_nominal_agr/C, adjunct_x_adjective(TargetAdj)/C, x_arg/[obl,3,A,D], prepsem(TargetPrep)/[D,B].

v_v_s_o2v_s_obl_o_adj(‘press-hold’, exercer, indef, pression, prolongé, sur). v_v_s_o2v_s_obl_o_adj(‘press-release’, exercer, indef, pression, bref, sur).

Third step: defining the target predicate and its arguments



Translation Cycles and Filtering

Source and target language markingFiltering ``spurious’’ ambiguity paths from optional rules


Reinstall the print head -- Remettre la tête d’impression en place

reinstall X ==> mettre X en place

Keep it in a safe place -- Rangez-la en lieu sûr

place ==> lieu

* Remettre la tête d’impression en lieu

Translation Cycles Source and Target Language Marking


Translation CyclesSource and Target Language Marking

Introduce source language parameters

pred(X,Pred) ==> pred(X,Pred,src).

Rewriting source into target predicates

pred(0,reinstall,src), +obj(0,_) ==> pred(0,remettre,trg), adjunct_x(0,1), pred(1,en,trg), arg(1,1,2), obj(1,2), ptype(1,sem), pcase(2,en), pred(2,place, trg), pers(2,’3’), num(2,sg), spec(2,3), spec_type(3,def).

Eliminating target predicate marking

pred(X,Pred,trg) ==> pred(X,Pred).


Reinstall the print head -- Remettre la tête d’impression en place

reinstall X (src) ==> mettre X en place (trg)

Keep it in a safe place -- Rangez-la en lieu sûr

place (src) ==> lieu (trg)

Remettre la tête d’impression en place

Translation CyclesSource and Target Language Marking


pred(A,need,src)

need ?=> il vous faut

pred(A,need,src) pred(A,falloir,trg) need ?=> il est nécessaire de

pred(A,need,src) pred(A, nécessaire,trg)

need ==> devoir

pred(A,devoir,trg)

Ambiguity paths introduced by optional rules


need ==> devoir

You need to perform periodic maintenance tasks. -- Vous devez effectuer périodiquement des tâches d’entretien.

You do not need to perform maintenance tasks.-- * Vous ne devez pas effectuer des tâches d’entretien.

-- Il n’est pas nécessaire d’effectuer des tâches d’entretien.

restriction/A :: -adjunct_x(A,B) ==> 0; +adjunct_x(A,B), -adjunct_type(B,neg) ==> 0.

SourceV ->TargetV :: pred(A,SourceV,src) ==> pred(A,TargetV,_), +vtype(A,_)&& restriction/A.

need -> devoir.


pred(A,need,src)




need ==> devoir

pred(A,need,src)

no applicationadjunct_type(_,neg)

Ambiguity paths introduced by optional rules

You do not need to perform maintenance tasks


pred(A,need,src)




need ==> devoir

pred(A,need,src)

Filtering ambiguity paths introduced by optional rules

``Stop’’ Predicate

pred(_,_,src) ==> stop.

Documents

Xerox Research Centre Europe 26/11/1998 LFG-based syntactic transfer from English to French with XTE The Xerox Translation Environment