PROSPECTS mOR PRACTICAL NATURAL LANGUAGE SYSTEMS 
Larry R. Harris 
Artificial Intelligence Corporation 
Newton Centre, ~ass. 02159 
As the author of a "practical" NL data base 
query system, one of the suggested topics for 
this panel is of particular interest to me. 
The issue of what hurdles remain before NL 
systems become practical strikes particulary 
close to home. %s someone with a more 
pragmatic view of NL processing, my feeling 
is, not surprisingly, that we already have the 
capability to construct practical ~:L systems. 
Significant enhancement of existing man- 
machine communication is possible within the 
current NL technology if we set our sights 
appropriately and are willing to take the 
additional effort to craft systems actually 
worthy of being used. The missing link isn't 
a utopian parsing algorithm yet to be 
discovered. The hurdles to practical NL 
systems are of a much more conventional 
variety that require, as Edison said, more 
perspiration than inspiration. 
It should be clear that none of my remarks 
conflict with the obvious fact that NL 
research has miles to go and that there are 
innumerable unresolved issues that will 
continue to require research beyond the 
foreseeable future. Our understanding of NL 
has merely scratched the surface, and it is 
fair to say that we don't even understand what 
all the problems are, muchless their solution. 
But by using the powerful techniques that have 
already resulted from NL research in extremely 
restricted micro-worlds it is possible to 
attain a high enough level of performance to 
be of practical value to a significant user 
community. It is these highly specialized 
systems that can be made practical using the 
existing technology. 
I will not speculate on when a general NL 
capability will become practical, nor will I 
speculate on whether the creation of practical 
specialized systems will contribute to the 
creation of a more general capability. The 
fact that there is a clear need for improved 
man-machine communication and that current 
specialized systems can be built to meet that 
need, is reason enough to construct them. 
The issue of whether practical specialized NL 
systems can now be built is, in my opinion, 
not a debatable issue. Those of us on this 
panel and other researchers in the field, 
simply don't have the right to determine 
whether a system is practical. Only the users 
of such a system can make that determination. 
Only a user can decide whether the NL 
capability constitutes sufficient added value 
to be deemed practical. Only a user can 
decide if the system's frequency of 
inappropriate response is sufficiently low to 
be deemed practical. Only a user can decide 
whether the overall NL interaction, taken in 
toto, offers enough benefits over alternative 
formal interactions to be deemed practical. 
If we accept my point that practicality is in 
the eyes of the user, then we are led to the 
inescapable conclusion that practical NL 
systems can now be built, because several 
commercial users of such a system \[Pruitt, 
O'Donnel\] have gone on record stating that the 
NL capability within the confines of data base 
query is of significant practical value in 
their environment. These statements plus the 
fact that a substantial body of users employ 
NL data base query in daily productive use 
clearly meets the spirit of a "practical" NL 
system. 
The main point of my remarks is not to debate 
the semantics of practicality, but to point 
out that whatever level of utility has been 
achieved, is due only in small part to the 
sophistication of the NL component. The 
utility comes primarily from a custom fitting 
of the NL component to the exact requirements 
of the domain; and from the painstaking 
crafting of the lexicon and grammar to achieve 
tha necessary density of linguistic coverage. 
In a sense, practicality is derived from a 
pragmatic approach that emphasizes proper 
performance on the vast bulk of rather 
uninteresting dialog, rather than focusing on 
the much smaller portion of intellectually 
challenging input. A NL system that is 
extrememly robust within well-defined 
limitations is far more practical than a 
system of greater sophistication that has 
large qaps in the coveraqe. 
~ttaining this required level of robustness 
and density of linguistic coverage is not 
necessarily as intellectually challenging as 
basic research, nor is it necessarily even 
worthy of publication. But let's not kid 
ourselves -- it is absolutely necessary to 
achieve a practical capability! It has never 
been clear to me that members of the ACL were 
interested in practical NL systems, nor is it 
clear that they should be. But I think that it 
is fair to say that there aren't many 
practical NL systems because there aren't very 
many people trying to build them! I would 
estimate, on the basis of my experience, that 
it takes an absolute minimum of 2 years, and 
probably more like 3 years, to bring a 
successful research prototype NL system to the 
level of practicality. This "development" 
process is well known in virtually all 
scientific and engineering disciplines. It is 
only our naivete of software engineering that 
causes us to underestimate the magnitude of 
this process. I'm afraid the prospects for 
practical NL systems look bleak as long as we 
have many NL researchers and few NL 
developers. 
Pruitt, J., "~ user's experience with ROBOT," 
Proceedings of the Fourth Annual ADABAS 
rJser's Meeting, April, 1977. 
O'Donnell, J., "Experience with ROBOT at 
DuPont," Natural Computer Conference Panel, 
May, 1980. 
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