Guided Sentences Composition for Disabled People 
Robert Pasero Nathalie Richardet Paul Sabatier 
Laboratoire d'Informatique de Marseille CNRS URA 1787 
Facult6 des Sciences de Luminy 163 Avenue de Luminy - Case 901 
13288 Marseille Cedex 9 - France 
{Robert-Pasero,Nathalie-Richardet2aul-Sabatier} @gia.univ-mrsfr 
Abstract 
We present the advantages of guided sentences 
composition for communicating in natural 
language with computers. We show how 
guidance can be achieved by means of the 
partial synthesis of sentences and describe our 
approach consisting in separating knowledge 
that comes under different levels of 
well-formedness and coroutining their 
treatment. This approach has led us to develop 
in Prolog a software, ILLICO, allowing for the 
conception of natural language interfaces with 
guided sentences composition. We present an 
application we have developed by means of 
ILLICO : KOMBE, a communication aid 
system for handicapped persons. 
1 Guided Sentences Composition 
We may distinguish two kinds of communication 
with natural language interfaces : 
- a "free" mode : the user types sentences without 
knowing the limits of the interface but he hopes 
he will be understood. Trivial reality : user's 
freedom will always be the freedom the system 
will grant him. 
- a guided mode : the system guides the user 
while he composes sentences. 
Unlike the "free" mode, with guided composition 
users quickly perceive the limits of the interface. The 
designer does not have to program all the expressions 
or structures having the same meaning. Unique forms 
and structures are sufficient. He may forget the others. 
Guided composition is a powerful principle for natural 
language interfaces to database and knowledge access, 
operating and command systems. This principle can 
also be applied to learning systems (natural languages 
or formal ones like database or programming 
languages). 
Expected tbrmulations can be provided to the user 
by means of partial synthesis of sentences. This 
principle was introduced by Alain Colmerauer within 
the French-English interface, Orbis, which was 
connected to a database on planets (Colmerauer and 
Kittredge, 1982). The same system is used for 
analyzing a given sentence and for synthesizing 
expected fomulations. Orbis is implemented in 
Prolog and illustrates in a convincing manner the 
potential reversibility of certain programs written in 
that language. 
We are concerned here with the partial synthesis of 
sentence from left to right. The main problem of this 
approach is that a word or an expression that has been 
synthesized by the system (and selected by the user to 
compose his sentence) must not lead to a future dead 
end. Theoretically, dead ends may issue from different 
levels corresponding to the differents levels of 
well-formedness of a sentence: lexical, syntactic, 
conceptual and contextual levels, in particular. 
As a result of formal language theory, we know 
that the emptiness problem is solvable for 
context-free grammars. So one can take all the levels 
of well-formedness into account simultaneously by 
merging them into one formalism, a context-free 
grammar with symbols reflecting lexical, syntactic, 
conceptual and contextual constraints, as it is done for 
instance in "semantic grammars". This is the case in 
Tennant's menu-based system (Tennant, 1984). 
The approach we have decided to follow is different. 
We are interested in (1) separating knowledge that 
comes under different levels (lexical, syntactic, 
conceptual) into distinct modules and (2) coroutining 
their treatment in order to avoid dead ends along the 
guided composition mode. 
2 ILLICO 
In our approach, knowledge is separated into four 
distinct modules : 
- a set of lexical rules (the lexicon) specifies 
expected words and expressions ; 
- in a restricted version of the Metamorphosis 
Grammar formalism (Colmerauer, 1975), a set of 
syntactic rules (the grammar) defines expected 
structures of sentences and grammatical 
agreements ; 
- by means of lambda-expressions operating on the 
semantic representation associated with relevant 
syntactic categories, a set of semantic rules allows 
the production of semantic representations ; 
- a set of conceptual rules (the conceptual model) 
defines domain constraints and connectivity 
constraints (Godbert et al., 1993). 
The algorithm for coroutining the treatment of the 
different kinds of knowledge in order to avoid dead 
ends along the guided composition mode is described 
in (Milhaud et al., 1992). 
Our approach has led us to develop in Prolog a 
software, ILLICO, allowing for the conception of 
natural language interfaces with guided sentences 
205 
composition. The following figure illustrates 
general principle of the approach. 
I Syntactic Parsing/Synthesis 
rules 
ENGINE 
I Semantic 
rules 
C User Interface I Conceptual I Model 
the 
1 
4 The KOMBE System 
In the framework of the EC TIDE program, we have 
developped by means of ILLICO, a communication 
aid system for disabled people : the KOMBE system. 
KOMBE is devoted to Amyothrophic Lateral 
Sclerosis (ALS) patients (Guenthner et al., 1992). In 
addition to motor weaknesses, ALS patients, mainly 
elderly people, suffer from diseases of the central 
nervous system that entail increasing speech 
impairment and aggravate their living conditions. 
They have not lost their cognitive capacities but are 
unable to speek and some of them are unable to write 
and communicate only by eye movements. For this 
kind of disabled person, the computer-assisted aids 
developed so far offer the user relatively slow 
communication, composing sentences letter by letter 
or selecting a pre-formulated phrase or sentence. Some 
systems include a dictionary permitting the user to 
select whole words. Guided sentences composition is 
a more convivial way for them to communicate. Step 
by step, they can select on the screen for selecting 
words and expression dynamically synthesized by the 
system. Words and expressions generated by the 
system always lead to the construction of a lexically, 
syntactically and conceptually well-formed sentence. 
The following figures show an example of a partial 
composition of a sentence by an ALS patient 
communicating with a doctor. 
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Fonctlhhnement : 0 Llbre 0 C! ~) C2 
aeFou 
° 
&lo x 
6lh 'P Yl bl q zl 
co 
e i r ' ce* 
i S - col 
dJ t 
e k O . d' 
6 I d ? 
Gkn6ral 
beaucoup de dlfflcUlt~$ ~ \[Quill 
beeucoup de mal I~ 
beeucoup de peine 
boso|n ' Se(~ 
:ette 
de 
des 
des dlfflcultGs 
J' ai I 
\[\] E3 \[\] \[\] t' .-I t" e,,l (,- e,,l I,°,i,e;J I,*,,.) \[~,;~i 
Fonclioanlmenl : 0 LOire 
: G6n6ral 
o I • l o u obtealr :Ill 6 
w ouurlr g 6 x lenCher 
i;h p y plier IL 
k q Z )rorl~e 
C r ' irbsenter 
f S Iroflter 
t prolonger 
I-- I~eceook 
~- q redresser 
Saisie : EdiUon Guid~o 
O ci ® c2 
j' al besucoup do dlffl¢ull6l i I 
~3E3~3E3 f~-~fr~ ~ fniq~ 
For example, the patient can compose the sentence : 
J'ai beaucoup de peine d plier le genou gauche (It is 
difficuh for me to bend my left knee).ALS patients 
can compose sentences about several conceptual 
situations. The introduction of a new situation only 
needs the definition of the associated conceptual model 
and lexicon. The grammar and the other components 
of the system are domain independent. 
In order to resolve the big lexicon problem, the 
system proposes several "sub-lexicon" of non empty 
intersection. This thematic division is built on tree 
structure and operates on the lexicon level. 
Acknowledgments 
Parts of this work were funded by the French 
Minist~re de la Recherche et de la Technologie 
(ILLICO Project) and the EC TIDE (Technology 
Initiative for Disabled and Elderly people) program 
(KOMBE Project). Special thanks to Franz Guenthner 
and Karin Krtiger-Thielmann for their contributions in 
the KOMBE Project. 

References 

Colmerauer A. 1975. Metamorphosis Grammars. 
Natural Language Communication With Computers, 
Springer Verlag. 

Colmerauer A. and Kittredge R. 1982. ORBIS: Proceedings of the 9th COLING Conference. 

Godbert E., Pasero R. and Sabatier P. 1993. 
Specifying and Using Conceptual Constraints. 
Proceedings of the Fifth International Conference on 
Human-Computer Interaction, Elsevier. 

Guenthner F., Krtiger-Thielmann K., Pasero R. 
and Sabatier P. 1992. Communications Aids for ALS 
Patients. Proceedings of the 3rd International 
Conference on Computers for Handicapped Persons. 

Milhaud G., Pasero R. et Sabatier P. 1992. Partial 
Synthesis of Sentences by Coroutining Constraints 
on Differents Levels of Well Formedness. Proceedings 
of the 14th COLING Conference. 

Tennant H. 1984. Menu-Based Natural Language 
Understanding. Proceedings of the National Computer 
Conference. 
