|
Ans. A deterministic parser permits only one
choice (arc) for each word category. Thus, each arc will have
a different test condition. Consequently, if an incorrect
test choice is accepted from some state, the parse will fail
since the parser cannot backtrack to an alternative choice.
This may occur, for example, when a word satisfies more than
one category such as a noun and a verb or an adjective, noun,
and verb.
In deterministic parsers, care must be taken to make correct
test choices at each stage of the parsing. It can be facilitated
with a look-ahead feature, which checks the categories of
one or more subsequent words in the input sentence before
deciding in which category to place the current word. The
following figure depicts an example of deterministic parser:
|
|
Nondeterministic parsers permit different arcs to
be labeled with the same test. Consequently, the next test
from any given state may not be uniquely determined by the
state and the current input word. The parser must guess at
the proper constituent and then backtrack, if the guess is
later proven to be wrong. This will require saving more than
one potential structure during parts of the network traversal.
The following figure depicts an example of nondeterministic
parser:
|
AI
Contents
