Eckhard Bick - VISL

definitions on the ”target grammar” (i.e. the particular grammatical description of
Portuguese to be implemented by my system).
1.2 The parser and the text
This dissertation is a Janus work, both practical and theoretical at the same time, one
face mirroring and complementing the other. After all, a major point was simply
showing that “it could be done” - that a Constraint Grammar for a Romance
langugage would work just as well as for English.
As a practical product, the parser and its applications can speak for
themselves, and, in fact, do so every day – at http://visl.hum.sdu.dk/ - , serving users
across the internet. In what could be called the theoretical ortext part of this
dissertation, apart from discussing the architecture and performance of the parser, I
will be concerned both with the process of building the parser and with its linguistic
spin-off for Constraint Grammar and parsing in general, and the analysis of
Portuguese in particular. Both tool and target grammar will be discussed, with
chapter 3 focusing on the first, and chapter 4 focusing on the second.
Chapter 2 describes the system’s lexicon based morphological analyser, and since
the quality of any CG-system is heavily dependent on the acuracy and coverage of its
lexico-morphological input base, the analyser and its lexicon constitute an important
first brick in the puzzle. However, chapters 2.1, 2.2 and 2.3, which treat the
architecture of the program as such, as well as the interplay of its root-, suffix-,
prefix- and inflexion-lexica, are rather technical in nature, and not, as such,
necessary to understand the following chapters, which may be addressed directly and
individually. In 2.2.4, the Beast will raise its head in the section on the dynamic
lexicon, where non-word words like abbreviations, enclitics, complex names and
polylexical expressions are discussed, and the principle of structural morphological
heuristics is explained. 2.2.5 is a reference chapter, where morphological word
classes and inflexion features are defined, and 2.2.6 quantifies the analyser’s lexical
coverage.
Chapter 3 introduces the Constraint Grammar formalism as a tag based
disambiguation technique, compares it to other approaches, and discusses the types
of ambiguity it can be used to resolve, as well as the lexical, morphological and
structural information that can be used in the process. It is in chapter 3 that the ”tool
grammar” as such is evaluated, both quantitatively and qualitatively, with special
emphasis on level interaction and rule typology. Finally, the system’s performance is
measured on different types of text (and speech) data and for different levels of
analysis.
”Level interaction” is central to the concept of Incremental Parsing (or Progressive
Level Parsing) and addresses the interplay between lower level tags (already
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