0. Introduction

A grammar of a language must meet two distinct kinds of criteria of adequacy. On the one hand it must correctly describe the ‘structure’ of the language (i.e., it must isolate the linguistic units, and, in particular, must distinguish and characterize just those utterances which are considered ‘grammatical’ or ‘possible’ by the informant, including as a special subclass those of the analyzed corpus. On the other hand it must meet requirements of adequacy imposed by its special purposes (e.g., pedagogical, as a basis for comparative study, etc.), or, in the case of a linguistic grammar having no such special purposes, requirements of simplicity, economy, compactness, etc. ¹ Thus the linguistic analysis of a language L can be described as the process of determining the set of ‘grammatical’ or ‘significant’ sentences of L (i.e., of determining the extension of the predicate ‘grammatical in L’), or, in other words, it is the process of converting an open set of sentences--the linguist's incomplete and in general expandable corpus--into a closed ² set--the set of grammatical sentences-- and of characterizing this latter set in some interesting way. Accordingly we might distinguish and consider separately two aspects of the linguistic analysis of a language, a process of ‘discovery’ consisting of the application of the mixture of formal and experimental procedures constituting linguistic method, and a process of ‘description’ consisting of the construction of a grammar describing the sentences which we know from step one to be grammatical, and framed in accordance with the criteria related to its special purposes.