Example: noun phrases

The first example is a fragment of a rather simplistic grammar for english noun phrases. Each rule is exemplified by one or more examples.

NUMB :: sing; plur.

The feature expressing the number can take on two values: sing or plur.

RULE noun phrase (NUMB):
   noun part (NUMB).
 # EX the previous president

RULE noun phrase (plur):
   noun part (NUMB1), coordinator,
      noun phrase (NUMB2).
 # EX the president and his wife

These two rules express that a noun phrase consists of one or more noun parts combined by coordinators. In the latter case it is always plural.

RULE noun part (NUMB):
   determiner (NUMB), noun group (NUMB);
 # EX the red bag
   noun group (NUMB).
 # EX software engineering

This rule has a number of alternatives, separated by semicolons. The number of the determiner has to agree with that of the noun group.

RULE noun group (NUMB):
   noun (NUMB);
 # EX bag
   adjective, noun group (NUMB);
 # EX red bag
   noun group (NUMB1), noun (NUMB).
 # EX software engineering

Obviously, the last rule is ambiguous for a noun phrase consisting of three or more nouns, like software engineering conference. Other sources of ambiguity are found in the attachment of preposition phrases (not described here) and in lexical ambiguities (e.g. time as noun and verb). AGFL provides a number of mechanisms (penalties, lexical frequencies, syntactic probabilities) to help in finding the most probable analysis (rather than the set of all analyses).