What are signs, in linguistic terms? Do signs consist of other signs, in the way that sentences like Let's listen to Charlie Byrd! have constituents, or compound words like mousetrap repair shop owner are made up of other words? Or is the quality of being a sign rather a holistic one which only attaches to utterances or even dialogues in context, from `Hi' to the entire proceedings of a business meeting? The present approach to the theory of word formation (the ILEX approach) encompasses the following assumptions about signs:
There are interesting special cases. For example, the traditional phoneme is an inventorised item with no parts, no semantic interpretation and purely structural `meaning'; the morph cran in cranberry has no parts at the same rank (morphology), and no semantic interpretation (except in Norfolk, where it means `a basket of the type freshly caught herring are kept in'). Leprechaun items such as `zero morphemes' and `traces', for those who believe in them, have no parts and no phonetic interpretation, but a category and a semantic interpretation.
Recent work in syntax, notably within the paradigm of Head-driven Phrase Structure Grammar, HPSG (cf. [Pollard & Sag 1987], [Pollard & Sag 1994]), has revived a similar structuralist notion of sign to that outlined here, and formalised it as an attribute-value matrix (AVM). In this approach, a taxonomy (type hierarchy) of sign types is defined, from the most general type sign to the most specific types, individual words; each sign type is characterised by a set of appropriate attributes and appropriate values, and generalisations over more specific sign types are expressed by inheriting the properties of more general sign types along the branches of the sign taxonomy.
It is not yet clear how to integrate lexical problem areas into the word and sentence oriented (albeit lexicalistic) HPSG approach. The HPSG model contains three relevant kinds of entity: a base inventory of words, lexical rules of inflection, word-formation, subcategorisation and semantic selection which define an extended inventory of words, and principles of composition linking the `head-daughter' (head part) and the `complement-daughters' (modifier parts) of a phrase by concatenation and unification or other appropriate operation. Problem areas for this model currently still include the following:
The present study addresses these problems and proposes an integrated, sign-based solution to lexical explanations. In the following sections, an HPSG-related theoretical framework and an operational DATR model for this theory are used to describe English compounds: linguistic concepts closely related to HPSG are described and implemented with representation techniques from DATR. After a summary of the main directions in Inheritance Lexicon Theory, modelling conventions for the inheritance lexicon are characterised, a summary of lexical properties of the main types of English noun, in particular noun compounds, is given, followed by an account of the DATR lexical knowledge representation formalism. An operational DATR model for English nouns is discussed, and a sample analysis is presented. The main results and conclusions are outlined in the final section.