Eckhard Bick - VISL

4.6 The transformational potential of CG
4.6.1 Exploiting word based tag notation with string manipulation
tools
Technically, a Constraint Grammar rule can be regarded as a context dependent string
manipulation command to be executed by a computer on an ambiguously tagged
sentence. A whole sentence with all its words and tags could be written as one long line
of text, and a given CG rule could then be rewritten as an awk or perl language
substitution rule (s/.../..../g), using so called regular expressions to express optional or
dummy string segments, or to bracket-mark a string of characters for conditioned
deletion, repetition or movement. Thus, information from different levels of analysis
(morphology, syntax, semantics etc.), both form and function, can be represented in the
same formalism, and interact in transparent, string-based disambiguation process.
It seems only logical, after disambiguation, to go a step further and exploit the
text-tool friendliness of the tagging notation for other purposes, like corpus searches,
information extraction, IT-based grammar teaching and the like. All of the application
examples mentioned are about identifying, extracting and standardising string chunks
from a text context. Common UNIX tools like grep in conjunction with substitution
commands will do the job, and are, in fact, used at the applicational front end of my
parser. In theory, however, the CG-formalism itself could be applied to the same end.
The mapping operator, for example, could be used to mark corpus occurrences of
certain linguistic patterns (1a), which could then be extracted by a chained grepcommand.
A replace operator, as suggested in (Tapanainen, 1996), though non-existent
in the cg1-compiler and inflexible in cg2, could complement the mapping operator and
be used for notational standardisation (1b).
(1a) MAP (@EXAMPLE) TARGET (@#ICL-SUBJ>) (*-1 @SUBJ> BARRIER NON-ADV LINK
0 N) ; # Find an example of: a non-finite subclause functioning as subject that itself has a
subject noun, preceding the main verb with nothing but adverbs in between
(1b) REPLACE (KS) TARGET ("quando" ADV) IF (0 @#FS) ; # Replace the relative
adverbial reading of "quando" by a subordination conjunction reading if the word heads a finite
subclause
4.6.2 Theory dependent tag filters
One of the most recalcitrant problems of grammatical analysis, in both corpus
annotation and grammar teaching, is - from a practical point of view - the simple fact of
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