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Finnish OT Prosody. Lauri Karttunen CLS-41 April 7, 2005. Overview. Success of Finite-State Morphology Lexical transducers Two ways of describing morphological alterations Sequential (Chomsky & Halle 1968) Parallel (Koskenniemi 1983) Finnish OT Prosody Basic Facts - PowerPoint PPT Presentation
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Finnish OT ProsodyFinnish OT Prosody
Lauri KarttunenCLS-41April 7, 2005
OverviewOverview
Success of Finite-State MorphologyLexical transducersTwo ways of describing morphological alterations
Sequential (Chomsky & Halle 1968)Parallel (Koskenniemi 1983)
Finnish OT ProsodyBasic FactsFinite-state implementation of Kiparsky’s 2003 analysiswith the FST tool (Beesley & Karttunen 2003)Conclusion
Final thoughts
Computational morphologyComputational morphology
Analysis
leaves
leaf N Pl leave N Pl leave V Sg3
Generation
hang V Past
hanged hung
Two challengesTwo challenges
MorphotacticsWords are composed of smaller elements that
must be combined in a certain order:piti-less-ness is Englishpiti-ness-less is not English
Phonological alternationsThe shape of an element may vary depending
on the contextpity is realized as piti in pitilessnessdie becomes dy in dying
Morphology is regular (=rational)Morphology is regular (=rational)
The relation between the surface forms of a language and the corresponding lexical forms can be described as a regular relation.
A regular relation consists of ordered pairs of strings.leaf+N+Pl : leaves hang+V+Past : hung
Any finite collection of such pairs is a regular relation.
Regular relations are closed under operations such as concatenation, iteration, union, and composition.
Complex regular relations can be derived from simple relations.
Morphology is finite-stateMorphology is finite-state
A regular relation can be defined using the metalanguage of regular expressions.
[{talk}|{walk}|{work}] [% +Base:0 | %+SgGen3:s| %
+Progr:{ing}| %+Past:{ed}];
A regular expression can be compiled into a finite-state transducer that implements the relation computationally.
work+3rdSg --> works
k:k
t:t
a:a
a:a
w:wo:o
l:l
r:r
+Progr:i :g
+3rdSg:s
+Past:e :d
:n
+Base:
GenerationGeneration
talked --> talk+Past
k:k
t:t
a:a
a:a
w:wo:o
l:l
r:r
+Progr:i :g
+3rdSg:s
+Past:e :d
:n
+Base:
AnalysisAnalysis
Lexical transducerLexical transducer
veut
vouloir +IndP +SG + P3
Finite-state transducer
inflected form
citation form inflection codes
v o u l o i r +IndP +SG +P3
v e u t
Bidirectional: generation or analysisCompact and fastComprehensive systems have been
built for over 40 languages:English, German, Dutch, French,
Italian, Spanish, Portuguese, Finnish, Russian, Turkish, Japanese, Korean, Basque, Greek, Arabic, Hebrew, Bulgarian, …
How lexical transducers are madeHow lexical transducers are made
LexiconFST
RuleFSTs
Compiler
f a t +Adj
r
+Comp
f a t t e
Lexical Transducer(a single FST)composition
LexiconRegular Expression
RulesRegular Expressions
Morphotactics
Alternations
Two-level rules vs. rewrite rulesTwo-level rules vs. rewrite rules
compose intersect
FST
rule 1 rule 2 rule n...
Surface form
Lexical form
Koskenniemi 1983
Intermediate form
...
Surface form
Lexical form
rule 1
rule n
rule 1
Chomsky&Halle 1968
Rewrite rulesRewrite rules
Epenthesis
Harmony
Lowering
? u: t y ? A s
? u: t I y ? A s
? u: t u y ? a s
? o: t u y ? a s
Yawelmani Vowel Harmony Kisseberth 1969
Two-level constraintsTwo-level constraints
? u: t y ? A s
? o: t u y ? a s
Underlying representation controls all three alternations.
Epenthesis: Insert u or i (underspecification)Harmony: Rounding next to a round V of the same height.Lowering: Long u always realized as long o.
Rewrite Rules vs. ConstraintsRewrite Rules vs. Constraints
• Two different ways of decomposing the complex relation between lexical and surface forms into a set of simpler relations that can be more easily understood and manipulated.
• One approach may be more convenient than the other for particular applications.
Two-level model vs. OT Two-level model vs. OT
In some respects, the two-level model of Koskenniemi (1983) was ten years ahead of its time:Symbol-to-symbol constraints, not string relations like
rewrite rules.Rules can refer to both input and output contexts.Constraints on the output can be expressed directly.Concepts such as FAITHFULNESS can be expressed
straight-forwardly.
But two-level constraints were not violable and not ranked. All the constraints have to be satisfied to get any output.
OverviewOverview
Success of Finite-State MorphologyTwo strains
Sequential (Chomsky & Halle 1968)Parallel (Koskenniemi 1983)
Finnish OT ProsodyBasic FactsFinite-state implementation of Kiparsky’s 2003 analysiswith the FST tool (Beesley & Karttunen 2003)Conclusion
Final thoughts
Finnish Prosody: basic factsFinnish Prosody: basic facts
• The nucleus of a Finnish syllable must consist of a short vowel, a long vowel, or a diphthong.
• Main stress is always on the first syllable, secondary stress occurs on non-initial syllables.
• Adjacent syllables are never stressed.• Stressed syllable is initial in the foot.
ilmoittautuminen ‘registering’ (Nom Sg)(íl.moit).(tàu.tu).(mì.nen)
Ternary feet in FinnishTernary feet in Finnish
Stress that would fall on a light syllable shifts on the following heavy syllable creating a ternary foot.(ká.las).te.(lèm.me) ‘we are fishing’(íl.moit).(tàu.tu).mi.(sès.ta) ‘registering’ (Ela Sg)(rá.kas).ta.(jàt.ta).ri.(àn.sa) ‘his mistresses’ (Par Pl)
Can we get these facts to come out “for free”, from the interaction of independently motivated principles?
Yes!Paul Kiparsky “Finnish Noun Inflection” Generative Approaches to
Finnic and Saami Linguistics, Diane Nelson and Satu Manninen (eds.), pp.109-161, CSLI Publications, 2003.
Nine Elenbaas and René Kager. "Ternary rhythm and the lapse constraint". Phonology 16. 273-329.
Non-OT and OT solutionsNon-OT and OT solutions
It is possible to define a cascade of replace rules that produce the desired result.
http://www.stanford.edu/~laurik/fsmbook/examples/FinnishProsody.html
But, following Kiparsky, we are going to do OT today, and in a more elegant way than is shown at
http://www.stanford.edu/~laurik/fsmbook/examples/FinnishOTProsody.html
General StrategyGeneral Strategy
Input language
GEN
.o.
Compose the input languagewith GEN to produce amapping from each input formto all of its output candidates
Eliminate suboptimalcandidates by applyingconstraints in the rankedorder. At least one outputcandidate always survives.
Constraint 1
Constraint 2
By what finite-state operation?
Lenient Composition .O.Lenient Composition .O.
Let R be a relation that maps each input string to one or more outputs.
Let C be a constraint that eliminates some outputs.
R .O. C is the relation that maps each input string that can meet the constraint C to the outputs that meet C and leaves the rest of the relation R unchanged. (Karttunen 1998)
Is constraint ranking rule ordering in disguise?
Need a prolific Need a prolific GENGEN
ka.laka.láka.làka.(là)ka.(lá)ká.laká.láká.làká.(là)ká.(lá)kà.la
(kà.la)(ká).la(ká).lá(ká).là(ká).(là)(ká).(lá)(ká.là)(ká.lá)(ká.la) ☜(ka.là)(ka.lá)
kà.lákà.làkà.(là) kà.(lá)(kà).la(kà).lá(kà).là(kà).(là)(kà).(lá)(kà.là)(kà.lá)
kala ‘fish’ (Nom Sg) 33 candidates
Basic definitions 1Basic definitions 1
Using Parc/XRCE regular expression syntax:
define C [b | c | d | f | g | h | j | k | l | m |
n | p | q | r | s | t | v | w | x | z]; # Consonant
define HighV [u | y | i]; # High vowel
define MidV [e | o | ö]; # Mid vowel
define LowV [a | ä] ; # Low vowel
define USV [HighV | MidV | LowV]; # Unstressed Vowel
define MSV [á | é | í | ó | ú | ý | ä’ | ö’];
define SSV [à | è | ì | ò | ù | y` | ä` | ö`];
define SV [MSV | SSV]; # Stressed vowel
define V [USV | SV] ; # Vowel
Basic definitions 2Basic definitions 2
define P [V | C]; # Phone
define B [[\P+] | .#.]; # Boundary
define E .#. | "."; # Edge
define Light [C* V]; # Light syllable
define Heavy [Light P+]; # Heavy syllable
define S [Heavy | Light]; # Syllable
define SS [S & $SV]; # Stressed syllable
define US [S & ~$SV]; # Unstressed syllable
define MSS [S & $MSV] ; # Syllable with main stress
GEN 1GEN 1
define MarkNonDiphthong [ [. .] -> "." || [HighV|MidV] _ LowV, LowV _ MidV , i _ [MidV - e], u _ [MidV - o], y _ [MidV - ö] ];
Insert a syllable boundary between vowels that cannot forma diphtong: i.a, e.a, a.e, i.o, u.e, y.e, etc.
define Syllabify C* V+ C* @-> ... "." || _ C V ;
Insert a syllable boundary after a maximal C* V+ C* pattern that is followed by C V. For example, strukturalismi -> struk.tu.ra.lis.mi.
GEN 2GEN 2
define Stress a (->) á|à, e (->) é|è, i (->) í|ì,
o (->) ó|ò, u (->) ú|ù, y (->) "y´"|"y`",
ä (->) "ä´"|"ä`", ö (->) "ö´"|"ö`";
Optionally stress any vowel with a primary or secondary stress.
define Scan [[S ("." S ("." S)) & $SS] (->) "(" ... ")" || E _ E] ;
Optionally group syllables into unary, binary, or ternary feet when there is at least one stressed syllable.
define Gen [MarkNonDiphthongs .o. Syllabify .o.
Stress .o. Scan];
Demo!Demo!
regex {kala} .o. Gen (compose)
print lower-words (show output candidates)
print size (count them)
Kiparsky's nine constraintsKiparsky's nine constraints
ClashAlignLeftMainStressFootBinLapseNonFinalStressToWeightParseAllFeetFirst
Counting constraint violationsCounting constraint violations
We use asterisks to mark constraint violations. We need a way to prefer candidates with the least number of violation marks.
define Viol ${*};
define Viol0 ~Viol; # No violationsdefine Viol1 ~[Viol^2]; # At most one violationdefine Viol2 ~[Viol^3]; # At most two violationsdefine Viol3 ~[Viol^4];
This eliminates the violation marks after the candidate set has been pruned by a constraint.
define Pardon {*} -> 0;
Defining OT ConstraintsDefining OT Constraints
Three types:Unviolable constraints
Primary stress in Finnish
Ordinary violable constraintsLapse
Gradient alignment constraintsAll-Feet-First
Strategy:We define an evaluation template for each of the three
types and then define the individual constraints with the help of the templates.
Evaluation Template for Evaluation Template for Unviolable ConstraintsUnviolable Constraintsdefine Unviolable(Candidates, Constraint) [ Candidates .o. Constraint ];
Example:
define MainStress(X) Unviolable(X, B MSS ~$MSS);
# B is the left edge of the word or "(".# MSS is a syllable with a primary stress.
Evaluation Template for Ordinary Evaluation Template for Ordinary ConstraintsConstraintsdefine Eval(Candidates, Violation, Left, Right) [ Candidates .o.
Violation -> ... {*} || Left _ Right .O.
Viol3 .O. Viol2 .O. Viol1 .O. Viol0 .o. Pardon ];
where Viol0 is ~${*}, Viol2 is ~[[${*}]^2], etc. andPardon is {*} -> 0 deleting all violation marks.
Evaluation Template for Left-Evaluation Template for Left-Oriented Gradient AlignmentOriented Gradient Alignmentdefine EvalGradientLeft(Candidates, Violation, Left, Right) [
Candidates .o.Violation -> {*} ... || .#. Left _ Right
.o.Violation -> {*}^2 ... || .#. Left^2 _ Right
.o.Violation -> {*}^3... || .#. Left^3 _ Right
.o.Violation -> {*}^4 ... || .#. Left^4 _ Right
.o.Violation -> {*}^5 ... || .#. Left^5 _ Right
.o.Violation -> {*}^6 ... || .#. Left^6 _ Right
.o.Violation -> {*}^7 ... || .#. Left^7 _ Right
.o.Violation -> {*}^8 ... || .#. Left^8 _ Right
.O. Viol12 .O. Viol11 .O. Viol10 .O. Viol9 .O. Viol8 .O. Viol7 .O. Viol6 .O. Viol5 .O. Viol4 .O. Viol3 .O. Viol2 .O. Viol1 .O. Viol0 .o. Pardon ];
Clash, AlignLeft, MainStressClash, AlignLeft, MainStress
ClashNo stress on adjacent syllables.
define Clash(X) Eval(X, SS, SS B, ?*);
Align-LeftThe stressed syllable is initial in the foot.
define AlignLeft(X) Eval(X, SV, .#. ~[?* "(" C*], ?*);
Main StressThe primary stress in Finnish is on the first syllable.
define MainStress(X) Unviolable(X, B MSS ~$MSS);
FootBin, Lapse, NonFinalFootBin, Lapse, NonFinal
Foot-Bin Feet are minimally bimoraic and maximally bisyllabic.
define FootBin(X) Eval(X, "(” Light ") "|” ("S["." S]^>1, ?* ,?*);
LapseEvery unstressed syllable must be adjacent to a stressed syllable or to the word
edge.
define Lapse(X) Eval(X, US, [B US B], [B US B]);
Non-FinalThe final syllable is not stressed.
define NonFinal(X) Eval(X, SS, ?*, ~$S .#.);
StressToWeight, Parse, StressToWeight, Parse, AllFeetFirstAllFeetFirst
Stress-To-WeightStressed syllables are heavy.
define StressToWeight(X) Eval(X, SS & Light, ?*, ")"| E);
License-Syllables are parsed into feet.
define Parse(X) Eval(X, S, E, E);
All-Ft-LeftThe left edge of every foot coincides with the left edge of some prosodic
word.
define AllFeetFirst(X) [ EvalGradientLeft(X, "(", ~$"." "." ~$".", ?*) ];
Finnish ProsodyFinnish Prosody
Kiparsky 2003:
define FinnishProsody(Input) [
AllFeetFirst( Parse( StressToWeight(
NonFinal( Lapse( FootBin( MainStress(
AlignLeft( Clash( Input .o. Gen)))))))))];
FinnWordsFinnWords
regex FinnishProsody( {kalastelet} | {kalasteleminen} |
{ilmoittautuminen} | {järjestelmättömyydestänsä} |
{kalastelemme} | {ilmoittautumisesta} |
{järjestelmällisyydelläni} | {järjestelmällistämätöntä} |
{voimisteluttelemasta} | {opiskelija} | {opettamassa} |
{kalastelet} | {strukturalismi} | {onnittelemanikin} |
{mäki} | {perijä} | {repeämä} | {ergonomia} |
{puhelimellani} | {matematiikka} | {puhelimistani} |
{rakastajattariansa} | {kuningas} | {kainostelijat} |
{ravintolat} | {merkonomin} ) ;
Demo!
ResultResult
(ér.go).(nò.mi).a(íl.moit).(tàu.tu).mi.(sès.ta)(íl.moit).(tàu.tu).(mì.nen)(ón.nit).(tè.le).(mà.ni).kin(ó.pis).(kè.li).ja(ó.pet).ta.(màs.sa)(vói.mis).te.(lùt.te).le.(màs.ta)(strúk.tu).ra.(lìs.mi)(rá.vin).(tò.lat)(rá.kas).ta.(jàt.ta).ri.(àn.sa)(ré.pe).(ä`.mä)(pé.ri).jä(pú.he).li.(mèl.la).ni
(pú.he).li.(mìs.ta).ni(mä’.ki)(má.te).ma.(tìik.ka)(mér.ko).(nò.min)(kái.nos).(tè.li).jat(ká.las).te.(lèm.me)(ká.las).te.(lè.mi).nen(ká.las).(tè.let)(kú.nin).gas(jä’r.jes).tel.(mä`l.li).syy.(dèl.lä).ni(jä’r.jes).(tèl.mät).tö.(my`y.des).(tä`n.sä)(jä’r.jes).(tèl.mäl).(lìs.tä).mä.(tö`n.tä)
Two ErrorsTwo Errors
(ká.las).te.(lè.mi).nen (jä´r.jes).tel.(mä`l.li).syy.(dèl.lä).ni
The interaction of Lapse and StressToWeight does not produce the desired result in these cases.
What is wrong?What is wrong?
define Debug(Input) [
DebugStressToWeight(
NonFinal( Lapse( FootBin( MainStress( AlignLeft(
Clash( Input .o. Gen))))))) ];
regex Debug({kalasteleminen});
(ká*.las).te.(lè*.mi).nen <-- actual winner
(ká*.las).(tè*.le).(mì*.nen) <-- desired output
(jä´r.jes).tel.(mä`l.li).syy.(dèl.lä).ni(jä’r.jes).(tèl.mäl).li.(sy`y.del).(lä`*.ni)
The StressToWeight constraint eliminates some of the desired winning candidates.
ConclusionConclusion
Can we get Ternary feet in Finnish “for free”, from the interaction of independently motivated principles?We don’t know.
Optimality Prosody is computationally very difficult.The number of initial candidates is huge:
kalasteleminen 70653järjestelmällisyydelläni 21767579
Simple tableau methods do not work.Finite-state implementation guards against errors made by
a human GEN and EVAL.But even when an error can be pinpointed, the fix is
not obvious.Debugging OT constraints is as hard as debugging two-
level rules, in practice more difficult than rewrite systems.
Final ThoughtsFinal ThoughtsMorphology is a regular relation.
The composition of words (morphosyntax), morphological alternations, and prosody can be described in finite-state terms.
A complex relation can be decomposed in different ways.There are many flavors of finite-state morphology: Item-and-
Arrangement, Rewrite rules, Two-level rules, Realizational Morphology, Classical optimality constraints.
Computing with finite-state tools is fun and easy.We have sophisticated formalism for describing regular
relations, efficient compilers and runtime software.
‘Pen-and-pencil’ morphology badly needs computational support.It is difficult to get globally correct results relying on a handful
of interesting words, rules, and constraints.
ReferencesReferences
Kenneth R. Beesley & Lauri Karttunen, Finite State Morphology, CSLI Publications. March 2003. (Software included).
http://www.fsmbook.com/
Lauri Karttunen, "Computing with Realizational Morphology" in CICLing-2003, A. Gelbukh (ed.), Lecture Notes in Computer Science 2588, pages 205-216. Springer Verlag. 2003.