3506. An earlier version of this paper was presented at the 1965
context-sensitivity in a grammar but one should talk of
International Conference on Computational Linguistics, New York,
degrees of context-sensitivity. In order, therefore, to
May 19-21.
2
tions are pertinent in the case of a grammar having
parse natural-language data adequately, the parsing
sufficient context-sensitivity to serve the needs of syn-
system has to have not merely some fixed capability of
tactic recognition adequate for the machine translation
being sensitive to a certain range of contexts but a
of natural languages.
capacity to increase its context-sensitivity.
a) Since the table will tend to be increasingly com-
This means that the most significant alterations in
grammar rules from the standpoint of natural-language
plex because of the requirement of high context-sensi-
tivity, a dictionary-type binary lookup may no longer
parsing will not be those that affect the formation of
particular rules within the same format. Rather, those
be sufficient. Rather, it may become necessary to de-
vise an algorithm for searching the table in such a
alternatives that will really make a difference in the
way that the graduation of contextual conditions is
adequacy of the parsings of natural-language sentences
taken into account properly.
will be alterations of the format itself in terms of in-
b) Revisions of the rules in such a complex table
creasing the degree of context-sensitivity. This in effect
will not be as simple a matter as it seems, because it
means that the simplicity claimed for a separate table
of rules with a constant algorithm turns out to be il-
will no longer be obvious which of the rules is to be
modified in a given case, nor will it be obvious where
lusory, since the proponents of this concept of simplic-
in the table this rule can be found. Likewise, it will
ity admit that it applies only when the rules are held to
the same format.
not be obvious what contextual conditions will have to
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