MACHINE-READABLE DICTIONARIES, LEXICAL DATA BASES 
AND THE LEXICAL SYSTEM 
Nicoletts Calsolsri 
Dipartimento dl Lingu|stica, Universita dl Plsa, Pisa, ITALY 
Istituto di Linguistics Cornputssionsle del CNR, Piss, ITALY 
I should like to raise some issues concerning the conversion 
from a traditional Marhine-Readable Dictionary (MRD) on tape 
to a Lexical Data Base (LDB), in order to highlight some 
important consequences for computational linguistics which can 
follow from this transition. The enormous potentialities of the 
information implicitly stored in a standard printed dictionary 
or a MRD can only be evidenced and made explicit when the 
same data are given a new logical structure in a data base 
model, and exploited by appropriate software. 
A suitable use of DB methodology is a good starting point to 
discover several kinds of lexical, morphological, syntactic, and 
semantic relationships between lexieal entries which would 
otherwise have remained unexploited. Moreover, the 
transformation of a "very large-scale" MRD into a LDB 
provides the means of operating throughout the lexicon in a 
really extensive manner. I think in fact that an "almost 
exhaustive" approach to lexical facts is essential both for 
reliable investigations of a lexical system, and for many kinds of 
linguistic applications which cannot be restricted to a particular 
domain of discourse. 
The possibility of abstracting significant regularities from 
recurrent patterns of natural language definitions by means of 
suitable computational methods, and of reaching a 
formalization of a number of important structuring relations 
within the lexicon will be discussed. An overview of the 
"associative links" already produced in the Italian LDB, and of 
other allowable interconnections will be given. 
In a "relational" organization of a computerized dictionary 
with complex interlinked structures, each word acquires its 
meaning as a result of its position in some of the partitionings 
created by the formalized relations. When an entry is 
activated, all of its relations with other entries can be activated, 
too. Conversely, when a relation is activated, all of its linked 
concepts are made immediately available. Conceptual and 
linguistic information at many levels is thus interactively 
retrievable from the LDB following the appropriate pointers. 
I shall especially take into consideration those types of 
relations which can be of relevance not only for 
"Computational Lexicology" research, but also in a more 
general Computational Linguistics framework. An example is 
provided by derivational relationships which, when formalized, 
give rise to families of semantically and syntactically connected 
entries, linked to the same base-word node, and substitutable in 
different syntactic formulations of the same conceptual 
meanings. Another example concerns ease or argument 
relations, both (a) between lexieal items, and (b) governed by 
lexical items. From (a) 1 expect to achieve, from the natural 
language definitions, useful information on the different 
lexicalizatons of ease-slot fillers in the case-frames of typical 
actions. In contrast, with (b) I can establish an encoding with 
each entry-and often with each word sense-of information on 
its surface and deep case-argument structure. The utility of the 
extensive inclusion of similar information in a LDB which 
should be the input for a lexically driven parser, for machine 
translation, etc., is obvious. 
As a conclusion, it should be pointed out how a LDB must be 
considered at the crossroad between texts and system, and in 
this perspective some essential properties of a LDB must be 
stressed. A first property is "multifunctionalism"; it is 
connected to the role of interfaces to the LDB. We must tend 
towards creating 'a single' integrated system which, through 
many different interfaces, can be adopted for all the range of 
possible applications, and by all the possible users, where user 
means both a human user and a computer program. Another 
important property is that of being "multi-perspective." This 
property of multiple access can create something like a 
constellation of sublexicons, which altogether capture the many 
possible structures which can be observed in the lexical system, 
along many dimensions of relatedness. The mediating function 
of a LDB between system and texts can thus be considered as 
the mapping of lexical structures, of many kinds, on linear 
unstructured texts. 
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