Syntactic Theory

Lexical Rules

Lexical rules are a mechanism to reduce stipulation and redundancy and to capture generalizations in the lexicon. The lexicon lists basic lexical entries in the form of a lexical sequence whose second member is of type lexeme. Lexical rules relate these lexemes to the different words that can be derived from the lexemes, for example they relate a verb lexeme to its different inflectional forms. The output of the lexical rules are words which can be used to build syntactic structures.

Lexical Rules are modeled as feature structures of type lexical-rule (l-rule), which specify values for the features INPUT and OUTPUT. There are three subtypes of lexical rules: inflectional-rule (i-rule), derivational-rule (d-rule) and postinflectional-rule (pi-rule). The following list gives an overview of the properties of these rules:

• derivational rule:
  • of type d-rule
  • relates lexemes to lexemes
  • may change the syntactic category (e.g., drive (verb) -> driver (noun))
  • may change the ARG-ST (e.g., active verb -> passive verb)
  • may change the valence (as consequence of changing ARG-ST)
  • may change the index (e.g., drive (index: situation) -> driver (index: driver-argument of the situation))
  • may add predications to the RESTR list, but not remove any
  • for example, Present Participle L.R. (Lexical Rule), Past Participle L.R., Passive L.R., Agent Nominalization L.R.

• inflectional rule:
  • relates lexemes to words
  • of type i-rule
  • does not change the syntactic category
  • does not change the ARG-ST
  • does not change valence
  • does not change the INDEX
  • may add predications to the RESTR list, but not remove any
  • for example, Singular Noun L.R., Plural Noun L.R., 3rd-Singular Verb L.R., Non-3rd-Singular Verb L.R., Past-Tense Verb L.R., Base Form L.R., Constant Lexeme L.R.

• post-inflectional rule:
  • relates words to words
  • for example, Inversion L.R., Extraposition L.R.

Constant Lexeme Lexical Rule

The Constant Lexeme Lexical Rule is a lexical rule for noninflecting lexemes. It applies to lexemes of type const-lxm and, consequently, to all of its subtypes. The rule is special in that it does nothing except license requisite words from homophonous lexemes. The SYN, SEM and ARG-ST values are not changed. The OUTPUTs of this rule are words and thus subject to the Argument Realization Principle. The formalization of the Constant Lexeme Lexical Rule is given below:

from Sag/Wasow/Bender 2003