DEVELOPING THE COMMENTATOR, A COMPUTER SYSTEM SIMULATING 
VERBAL PRODUCTION 
Nilan Bily, Bengt Sigurd 
Department of Linguistics, University of Lund, Sweden 
The project "COMMENTATOR" at the department of general 
linguistics at the university of Lund is intended to test 
ideas about language production. The system implemented in 
BASIC on the ABC80 micro-computer generates a scene on the 
monitor where two persons, Adam and Eve, move randomly around 
a gate. Not only the present positions of Adam and Eve are 
shown on the screen but even the positions before the last 
Jump. This setting is also used for eliciting comments from 
human subjects. The moves are generated randomly but the oper- 
ator can choose the length of the Jumps. The initial place- 
ment of Adam and Eve can be determined by the operator, as 
well as the instructions for the machine concerning the focus 
of attention (Adam or Eve) and the primary goal of the actors 
(the gate or the other actor). On the operator's command the 
computer produces a set of written comments on the development 
of the scene. COM~ENTATOR is a research tool, and does not use 
any ready-made sentences describing forseable situations. 
The system works as follows: From the primary information 
(the coordinates of the gate and the two actors) some more 
complex values are derived (distances, relations "to left", "to 
right" etc.). The conditions for using abstract predicates 
equivalent to "to left" etc. in the given situation are tested 
accoMin 6 to a question menu. This results in positive or 
negative abstract sentences. The abstract sentence constituents 
- 42 - 
are ordered as sub.leers, predicates , and oh,leers. Connective 
elements, such as "also", "either", "yet", are added If possib- 
le. These connect the last proposition to the previous ones. 
Proper namesp pronouns, or other NPs are chosen on the 
basis of reference relations to the preceding proposition. The 
abstract propositions are substituted by surface phrases and 
words. The assembled structure is printed. (For a more extens- 
ive description of the program and one version of t~e prepare 
itself see Sigurd 1980.) 
The text produced by COMMENTATOR may look like this: 
Eva ~r till h~ger om Adam. (Eve is to the right of Adam.) 
Hen ar till vanster om henne. (He Is to the left of her.) 
Hen ~r till vanster om porten cokeS. (He is to ~he left of the 
gate, too.) 
Hen n~zmar slg den. (He is approaching it.) 
Hen n~u~na~ sig Eva coke&. (He is approaching ~re, too.) 
Hen ~r n~rmast porten dock. (Lit. She is closest to the gate, 
however. ) 
Hen ~r inte n~ra den. (She is not close to it.) 
Adam ~r lnte n~ra den heller. (Adam is not close to it, either.) 
COMMIE 
COMMIE is a semantically and psychollngulstlcally more 
advanced program, which is intended to overcome certain short- 
comlngs experienced with the original COMMENTATOR. This more 
complex pro~am generates a more sophisticated and more dynamic 
stimulus including more objects and persons on the scene and 
the vocabulary is about ten times larger. COMMIE is to produce 
human-like texts. One important task is to avoid unnecessary 
redundancies. The commentaries produced have to be based on 
relevant changes of the scene and they must avoid repetitions, 
including information implied by previous utterances. (g.g., 
"Adam is to the left of Eve" implies "Eve is to the right of 
Adam", etc.) Not all propositions that ere not true in the 
given.moment deserve to be mentioned, either. Negated state- 
- 43 - 
ments are meaningful only as answers to expectations evoked 
by the pre~ou8 context. (E.g., "Bertil is chasing Eve. He is 
not ver~ near her yet, however." but not l"Bertil is chasin K 
Eve. Neither of them is in the .upper riEht corner".) 
All information about the world of the ~V screen is 
stored in a two-d~nensione£ array as mi~L-thouKhte - two-place 
predications that are either true or false at the given moment. 
Yorgettln8 is s~nulated by 8radu~lly letting the contents of 
the array pass a horizon of forgetting. In a future version 
the basic contents may be stored in & lon8 term memory. The 
p~ed£cations of the array serve 88 inputs for generati~ complex 
semantic structu~res, which are inputs to the production of 
commentaries proper. Referring in OOU~IE is to be based on the 
theory of FSP. By computiz~ "de~rees of ~Lveness", it shoUld 
be able to cope with even such problems as the difference 
between thematic pronominal vs. thematic zero subjects in 
Sla3~o langusKes generally or the enclitio vs. full forms of 
oblique pronominal cases in West Slavic le~gue~es etc. (Cfe 
Bily 1981a, Chapter Three.) The deep structures are to be 
"univers8~" enough to allow generation of comments~es in 
several' lan~ae~es. 
COMMIE will also have more sophisticated conditions for 
the use of the two-place predicates. Instead of, e.g., purely 
geometrically defined conditions for "X is to the left of Y" 
to be true, a certain limit is put on the allowed vertical 
distance. The limit seems to be a function of the size of X 
and ¥, the size of the referential frame and the focus of 
attention. (Cf. Bily 1981b) 
Other versions in preparation 
A version produclnE spoken comments using VOTRAX speech 
synthesizer or more advanced technique ie being planned. As 
the COM~NTATOR has perfect control of the steps in the produat- 
ion of comments, it should be able to produce better prosody 
than ordinary text-to-speech systems (e.g. Carlson et 81. 
- 44 - 
1981). Contractive accents can be derived as the system knows 
if a comment is in contrast with a precidAng statement, 
Accents based on syntactic structure can be derived Am the 
syntactic structure of the comments if prefectly known, 
A system which can comment on asp arbitrary scene where 
persons and things appear, 8ctions and events take p~ace, 
would demand pattern recognition, which is a difficult problem. 
0nly a smeA1 scale system is being planned. It requires a 
flexible question menu, where "relevant questions are produced 
successively, Beginning comments on such a scene would be 
something like this: "There is something at the left upper 
corner. Zt moves. Now something turns up at the right upper 
corner . It looks like a ship. Both objects move fast towards 
the centre." Such comments suggest applications as the auto- 
matio radar 0ommen~ator, but so far such practical applAoat- 
ions have been little considered. It is, however, envisaged 
that verbal comments on events produced by computers will be 
oonunon in the future world of robots. 

Bibliography

Blly, M. (1981a) : "Zntraoentential I>z'ono~Lnalizat£on and 
Functional Sentence Perspective (in Czech, Russian, and 
English)", Lund 81avonic Monographs 1, UnAversity of 
Lund.

(1981b): "Experience with COMMENTATOR, a Computer Systa~n 
Simulating Verbal Behsviou~", in Lien, E° (ed°) "De Nor- 
diske Datalingvietikkdagene 1981", p. 39-46.

Carlson, .R. et al. (1981): "A Multi-Language Portable Text-to- 
-Speech System for the Disabled", Journal of BiomediceA 
Engineering 1981:3.

Sigttrd, B. (1980): "C0~TATOR. A Computer System Simulating 
Verbal Behaviou.r", Dept. of Linguistics, University of 
Lund, .mimeographed.
