1. Towards Parsing Croatian Complex Sentences: Dependent Noun Clauses
Vanja Štefanec, Kristina Vučković, Zdravko Dovedan
University of Zagreb, Faculty of Humanities and Social Sciences
{vstefane, kvuckovi,
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2. Our goal
to determine the boundaries of dependent clauses within the complex sentence
focusing the parser
performing disambiguation of chunks
improving the chunker
to test the adequacy of this model as a pre-parsing method for complex sentences
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3. Overview of the work
grammar that can recognize the dependent noun clause (object clause) in the complex sentence
both simple object clause and coordination of object clauses
by defining the co-text in which object clause can occur
NOT by describing its structure
relying on
output of the chunker
conjunctions, complementizers, punctuations, ...
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4. Object clauses in Croatian
very frequent
refer to their superordinate clause predicate as a direct object
three types (according to grammars)
relative (odnosne)
interrogative (zavisnoupitne)
declarative (izrične)
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5. Relative object clauses
introduced by relative pronouns and adjectives
Jeste li našli [što ste tražili]?
Have you found [what you’ve been looking for]?
Kupit ću [kakvog nađem].
*I will buy [of the kind I’ll find].
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6. Interrogative object clauses
general (općeupitne)
introduced by interrogative conjunctions ‘li’, ‘da li’ or by interrogative pronouns (‘tko’, ‘koji’, ‘čiji’, ‘što’, …)
Još ne shvaćaš [što se dogodilo].
You still don’t understand [what happened].
Zaboravio sam [koji je danas dan].
I forgot [which day it is].
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7. Interrogative object clauses
of place (mjesne)
introduced by interrogative adverbs of place
Recite [kamo ste se zaputili].
Tell us [where you are headed].
of time (vremenske)
introduced by interrogative adverbs of time
Nisu rekli [kad će doći].
They didn’t say [when they’ll be coming].
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8. Interrogative object clauses
of manner (načinske)
introduced by interrogative adverb ‘kako’
Još nismo saznali [kako se to dogodilo].
We still haven’t found out [how that happened].
qualitative (kvalitativne)
introduced by interrogative adjectives ‘kakav’, ‘kakva’, ‘kakvo’
Ne znam [kakav si ti to čovjek].
I don’t know [what kind of a person you are]?
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9. Interrogative object clauses
of amount (količinske)
introduced by interrogative adverb ‘koliko’
Znaš li [koliko si već popio]?
Do you know [how much you drank already]?
of cause (uzročne)
introduced by interrogative adverbs of cause or prepositional expressions ‘zašto’, ‘zbog čega’, …
Ne razumijem [zašto si zakasnio].
I don’t understand [why you are late].
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10. Declarative object clauses
introduced by conjunctions
‘da’ (most common)
‘kako’ (less frequent; stylistic variant of ‘da’)
‘gdje’ (extremely rare; very stylistically marked)
Obećao si [da ćeš doći].
You promised [that you’ll come].
Rekli su [kako ga nije briga].
They said [that he doesn't care].
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11. Object clauses in Croatian
have to be preceded by a transitive verb in an active voice form
impossible to predict their function by observing only the structure
(Vidio sam)PRED ([da se igra])OBJ.
I saw that he’s playing.  object-clause
(Vidio sam)PRED (ga)OBJ ([da se igra])ATTR.
I saw him playing.  adjective clause
(Izišao je)PRED (van)ADV ([da se igra])ADV.
He went out to play.  purpose clause
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12. Object clauses in Croatian
can be easily confused with subject clauses
subject clauses refer either to the nominal predicate or verbal predicate in passive voice forms
(Poznato je)PRED ([da pušenje uzrokuje rak])SUBJ.
It is well known that smoking causes cancer.
(Kaže se)PRED ([da je bolje spriječiti nego liječiti])SUBJ.
It is said that it is better to be safe than sorry.
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13. The model can be divided into four parts the predicate
what can appear between the predicate and object clause
object clause
what can appear after the object clause 1. 2. 3. 4.
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14. 1. the predicate
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15. 2. between predicate and the clause
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16. 3. object clause - conjunctions
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17. 3. object clause - body
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18. 4. after the object clause
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19. Examples Dodao je ([da približavanje Hrvatske EU ima dvije faze]).
Pretpostavimo ([da imate visoke demokratske standarde], [da manjine imaju puna prava], [da su medijske slobode savršene])...
Zato savjetuje svima koji namjeravaju podići kredite ([da malo pričekaju, ako to mogu]).
Odgovarajući na pitanje hoće li na dogovore iz Mokrica djelovati skorašnji slovenski lokalni izbori, Maštruko je rekao ([kako u to ne vjeruje] te [da bi u slučaju kad bi države svaki put čekale ([da prođu izbori]), pregovaranje bilo nemoguće]).
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20. Problems chunker can not identify the whole VP undisambiguated chunks
subject clauses
some verbs can take two arguments in accusative case
‘pitati’ (to ask), ‘učiti’ (to teach), ...
adjective clauses, purpose clauses
identifying the level of subordination
often problem beyond syntax
rules of orthography
proper use of punctuation marks (comma, dash)
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21. Evaluation performed in ideal circumstances
predicate is correctly identified (i.e. chunked)
information about verb valency is present
corpus consists of 174 sentences with 215 object clauses
PRECISION
RECALL
F-MEASURE
0,46
0,82
0,59
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22. Evaluation low precision
BUT correct identification in 91% of the cases
average number of results per clause is 2,15
disambiguation!
high recall
confirms the adequacy of the model
AND we have identified the critical cases so improvements can also be expected
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