Biblioteka Cyfrowa KLF UW (Digital Library of the Formal Linguistics Department at the University of Warsaw)

[w:] Papers in Computational Linguistics I, Janusz S. Bień (ed.

Bień, Janusz S.

Laus-Mączyńska, Krystyna

Szpakowicz, Stanisław

Parsing Free Word Order Languages in Prolog

Siemień, Joanna

Institute of Informatics Biennal Report 1980 and 1981

Hajičová, Eva

TOWARD A PAP~I'NG METHOD FOR FREE WORD O ~  LANGUAGES x
Janusz S. Hte~, StantsZaw Szpakowioz 
Ins t i tu te  of  In fo rmat ics ,  Warsaw Un ivers i ty  
P.0.H. 1210, 00-901Warezawa, Poland 
,,Free word order" is a traditional term that should not 
be taken literally. However, we shall retain the term for its 
conciseness. 
Formal descr ip t ions  o f  =yntax have been usua l ly  based 
e i ther  on the immediate const i tuents  or  on the  dependency 
p~ilosophy. Neither of them seems directly applicable to free 
word order languages. The intertwining phrases cannot be de- 
scribed naturally by IC rules. Some coordinate constructions 
are difficult to describe by me~us of dependency relations. 
In  our op in ion ,  parsers  fo r  f ree  word order  languages should 
not  be based on the methods developed w i th in  the IC framework. 
Scarce exper iments  wi th  parsers  based on the dependency form- 
a l i sm,  eg. /5 / ,  do not  seem promis ing.  There fore ,  we dec ided 
to take  a f resh  s ta r t  and to  a t tack  the problem by reana lys -  
ing  the bas ic  not ions  of  syntax and pars ing .  We focus our 
a t tent ion  on those formal  aspects  of  a language system which 
might be most use fu l  fo r  automat ic  text  p rocess ing .  We assmae 
that  the morpho log ica l  leve l  i s  descr ibed  a long the l ines  of  
/2/4 
x) This paper is an extended abstract of /3/. 
- 37  - 
2. The Notion of S.~t_ax. 
In  th i s  paper,  we understand syntax as the domain of 
forr~al re la t ions  between words, i .e .  roughly  as so -ca l led  
sur face  syntax.  We def ine  the not ion  us in~ a morphology-based 
c r i te r ion ,  descr ibed  below. 
The outcome of morphological  ana lys i s  can be ambiguous 
fo r  an i so la ted  word. In  most s i tuat ions ,  however, the  morpho- 
log ica l  features  of a word are un ique ly  determined by some 
fo rmal  proper t ies  of i t s  context .  
Sometimes the ambigui ty  remains ,  as in  the fo l low ing  
sent  enc e 
Op~nien ie  bryg~d piecowyoh spowodowa~o potgp ien ie  wuJa Jana.  
1 I I ! ! , , .  I ! ! I 1 
" ~  l~gen" V - ' ~  NPgen" 
! 1 I 1 
~nom./aco. ~nom./ac£. 
There are f i ve  independent  ambigu i t ies  in  th i s  sentence ,  
y ie ld ing  32 coherent  read ings .  Two of them are due to She 
neut ra l i za t ion  of agent /pat ient  funct ion  dur ing  nomina l i sa t~ 
ion .  For example, "potgp ien ie  x" means "d isapprova l  of ~ '  
(e i ther  "x d isapproves y" or "y d isapproves  x" ) i  such an 
ambigu i ty  can be reso lved  only  by exsmining the meav.ing of a 
g iven phrase,  so we ca l l  i t  semantic one. 
The next ambiguity Occurs in the phrase "wuJa Jana", 
that means either "uncle John"gen ° or "John's uncle"gen.O 
Here we can see two kinds of syntactic relations: case agreem- 
ent (the former interpretation) or government (the latter 
one), which both require "Jana" to be in genitive case. Such 
an ambi~ulty we consider as purely syntactic one. 
In the phrase "bry~d plecowych" we call discern either 
case agreement ("piecowych"gen" is then an adjective) or 
government ("piecowych"gen ° is then a noun). Here, the elim- 
ination of morphologica l  homon~my g ives  r i se  to a l te rnat ive  
const ruct ions ,  thus inc reas ing  the syntact i c  ambi~i ty ,  
-38 -  
The last ambiguity stems from the nominative/accusatlve 
neutralization both of a virtual subject and a virtual object 
of the sentence. It suffices to assign a syntactic function 
to one of them~ the function of the other and the morpho- 
logical characteristics of both of them will be fully determ- 
ined. 
The example demonstrates how certain relations between 
sentence components allow to disambiguate the morphological 
properties of individual words without resorting %0 their 
meanings. In our approach, these relations constitute the 
level of syntax /3/. 
Syntactic relations (eg. agreement, government) consist 
in matching syntactic properties (eg. case, gender) of re- 
speotiveu units. The basic unit is a morphological word /2/. 
By the syntactic structure of a sentence we understand 
some explicit representation of all the syntactic relations 
between its components, usually - a graph. Such a graph need 
not necessarily be connected. For example, some modifiers are 
linked to their heads only by semantic relations and not by 
syntactic ones. Similarly, some elllptio sentences may have 
disconnected syntactic representationu. 
We ~ulderstand parsing as a process of establishing all 
syntact i c  s t ruc tures  of  a g iven  text .  A l though such s t ructur -  
es a re  ra ther  unsoph is t i ca ted ,  they  are  pract i ca l ly  very  
important for low-level text processi~. 
In search of an adequate parsing method, we found the 
idea of ~arcus /4/ most appealing. He claims that natural 
languages are designed to be deterministically parsed from 
left to right and that writing a grammar should consist in 
finding out local clues which enable the parser to select 
properly what to do next. This idea seems even more advantag- 
eous for free word order languages. Rich inflection makes 
- 39  - 
the  loca l  c lues  much more exp l i c i t  and the pareer ' s  expectat -  
ions  more prec i se .  Bes ides ,  such an organ isat ion  of  the  pars -  
ing  process  i s  compat ib le  wi th  the resource  cont ro l  hypothes-  
i s  /1 /  which i s  hoped to account fo r  semantic  imp l i ca t ions  of  
f ree word order.  
~ Conclus ion 
As a pract i ca l  consequence of  the cons iderat ions  g iven  
above, we adopt the fo l low ing  research  program. As a s ta r t ing  
po int  we take the ex is t ing  IC-based syntact i c  descr ip t ion  of  
Po l i sh  sentences  w i th  neut ra l  word order  /6 / ,  cons i s t ing  of  
about 500 ru les  (some pv~ts of  i t  have been rewr i t ten  in  g reat -  
er  deta i l  /7 / ,  w i th  the number of  ru les  inc reas ing  5-10 t imes) .  
We are going to res t ruc ture  the descr ip t ion  to obta in  an index 
of  expectat ions  re la ted  to each syntact i~  un i t .  We sha l l  in -  
corporate  the c lues ,  thus  obta ined ,  in to  some Marcus -s ty le  
pars ing  s t ra te~.  We expect  that  i t  w i l l  l ead  to  an e f f i c ient  
and l ingu is t i ca l l y  sound parser  fo r  Po l i sh .  
References  
/ l J  Bien J .S . :  A P re l im inary  Study on L ingu is t i c  Imp l i ca t ions  
of  Resource Cont ro l  in  Natura l  Language Unders tand ing .  
ISSCO Working Paper 44, Geneve 1980. 
/2 /  Bien J .S . ,  Sa lon i  Z . :  The not ion  of  morpho log ica l  word 
and its application to the description of Polish inflect- 
ion (preliminary version) /in Polish/. l~ace Pilologicz- 
ne XXXI, to  appear .  
/3/ Bien J.S,, Szpakowlcz S. : Toward a Parsing Method for Free 
Word Order Languages. In: Papers In Comphtetlonal Linguls- 
tics II. IInf UW Repor ts ,  to  appear .  
/4/ Marcus M.P,: A Theory of Syntactic Reco~lition for Natur- 
al Language. ~LIT Press 1980, 
/5/ Panevov~ J., Sgall P, : On Some Issues of Syntactic Anal- 
ysis of Czech. In: The l~e~ue Bulletin of Mathematical 
Lingulstlcs 34, 1980, 21-32. 
40 - 
[6/ Szpakowioz S. :  Formal syntact ic  descr ipt ion of Pol ish 
sentences / in  Po l i sh / .  Wydawnictws Uniwersytetu Warszaw- 
skiego~ in press.  
/7 /  Szpakowicz S. ,  gwidzi~ski M. : An out l ine of sentenqs 
schemes c lass i f i ca t ion  in contemporary wr i t ten Pol ish 
/ in  Po l ish/ .  Studia ~-~amatyczne V, WrooXaw, to appear. 
- 41  - 


English

Towards a parsing method for free word order languages

Rogowska, Marianna

[Recenzja:] Barbara Bartnicka, Roksana Sinielnikoff, Słownik podstawowy języka polskiego dla cudzoziemców, Wydawnictwa Uniw. Warszawskiego, 1979, s. 342

Kopczyński, Andrzej

Hamftwurcel, Anatol

Karska, Ewa

Rywin, Lew

Toward computerized dictionaries for inflexional languages. External design philosophy

w: Papers in Computational Linguistics II (red. J. S. Bień

Toward Computational Description of Written Polish

On Surface-Syntactic Analysis of Polish

Papers in Computational Linguistics II (redakcja)

Bibliografia Instytutu Informatyki Uniwersytetu Warszawskiego za rok 1980

Streszczenie referatu zaproszonego na:

VI Ogólnopolskie Seminarium Metodyczne Informatyki

RYNIA 26-30 maj 1981 r

Komunikacja człowieka z komputerem w języku naturalnym

University of Warsaw

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