On lexical entries and lexical representations

Lexicalist models of syntax share with lexeme-and-paradigm models of morphology the as-
sumption that the primary unit of the lexicon is the lexeme, an abstract representation of
properties unifying a set of inflected word forms. Lexicalist syntactic models (such as Head-
driven Phrase Structure Grammar, henceforth HPSG, and Sign-Based Construction Gram-
mar, henceforth SBCG) distinguish modelled linguistic objects from descriptions of objects.
A description, but not an object, can be a partial (underspecified) representation. However,
a lexeme is by definition only partially specified, being underspecified for all those mor-
phosyntactic properties that its word forms realize (the lexeme dog realizes neither singular
nor plural, unlike the word forms dog, dogs). This implies that lexemes are descriptions, not
objects, which is incompatible with assumptions about the type hierarchy for signs and the
lexicon in HPSG/SBCG. If we relax the definition of full specification to admit lexemes as ob-
jects then the question arises as to how many properties can be left unspecified. I argue for
a maximally underspecified model. Even the declaration of properties for which the given
class of lexemes inflects (the ‘morpholexical signature’, morsig) is underspecified to the ex-
tent that its contents are predictable. This entails that an inflected word form of a lexeme
can be defined only after the morsig attribute is specified. Derivation, a lexeme-to-lexeme
mapping, can therefore be defined over the same maximally underspecified lexical represen-
tations, whose inflection is then typically governed by a different morpholexical signature
(e.g. when the derivation changes word class). All such specifications are given by default
statements, which are overridden for irregular items. Verb-to-adjective transpositions (par-
ticiples) are members of the verb’s paradigm yet inflect according to the adjectival paradigm
(the ‘adjectival representation’ of a verb). This gives the effect of a ‘lexeme-within-a-lexeme’,
posing a challenge for lexeme-and-paradigm models. I present an analysis in which the def-
inition of the participle is driven by a feature representation. This (re-)defines the morsig
attribute, creating a representation which is identical to that of an adjective, while remain-
ing part of the verb’s paradigm. I discuss some of the implications of this analysis for lexical
relatedness, the lexical type hierarchy of SBCG and the morphology-syntax interface.