EDBL: a general lexical basis for the automatic processing of Basque

I. Aldezabal, O. Ansa, B. Arrieta, X. Artola, A. Ezeiza,
G. Hernández, M. Lersundi

Dept. of Computer Languages and Systems
University of The Basque Country
649 p.k., 20080 Donostia (Basque Country)
jiparzux@si.ehu.es

EDBL (Euskararen Datu-Base Lexikala) is a general-purpose lexical database
used in Basque text-processing tasks. It is a large repository of lexical
knowledge (it has currently more than 75,000 entries) that acts as basis
and support in a number of different NLP tasks, thus providing lexical
information for several language analysis tools: morphological analysis,
spell checking and correction, lemmatization and tagging, syntactic
analysis, and so on. The lexical database has been designed to be neutral
in relation to the different linguistic formalisms, and flexible and open
enough to accept new types of information. A recently implemented
browser-based user interface makes easy to the lexicographer the job of
consulting the database, correcting and updating entries, adding new ones,
etc.

The paper presents the conceptual schema and the main features of
this database, discussing some problems encountered in its design and
implementation in a commercial DBMS.

Extended Entity Relationship diagrams are used to explain the conceptual
schema of the database. Given the diversity of the lexical entities and
the complex relationships existing among them, three total specializations
have been defined under the main class of the hierarchy. The first one
divides all the entries in EDBL into standard and non-standard entries:
being Basque a language still in course of standardization, processes such
as spelling checking and correction, non-standard language analysis, etc.
require information about non-standard entries and their relationships
that must be stored in the lexical database. The second one divides the
units in the database into dictionary entries (classified into the
different parts-of-speech) and other entries (mainly non-independent
morphemes and irregularly inflected forms). Finally, another total
specialization has been established between single-word entries and
multiword lexical units; this permits to describe the morphotactics of
single-word entries, and the constitution and surface realization schemas
of multiword lexical units.

A hierarchy of typed feature structures (FS) has been designed to map the
entities and relationships in the database conceptual schema. The FSs are
coded in TEI-conformant SGML, and Feature Structure Declarations (FSD)
have been made for all the types of the hierarchy. Feature inheritance is
employed in these FSDs in order to make the definition of each type more
consistent and comfortable.

The FSs are used as a delivery format to export the lexical information
from the database. The information coded in this way is subsequently used
as input by the different language analysis tools.