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<Paper uid="C90-3092">
  <Title>ANTICIPATION-FREE DIAGNOSIS OF STRUCTURAL FAULTS Wolfgang Menzel Zentralinstitut fQr Sprachwissenschaft Akademie der Wissenschaften der DDR</Title>
  <Section position="1" start_page="0" end_page="0" type="abstr">
    <SectionTitle>
ANTICIPATION-FREE DIAGNOSIS OF STRUCTURAL FAULTS
</SectionTitle>
    <Paragraph position="0"> Current attempts to diagnose grammatical faults in natural language utterances are except for agreement errors and certain cases of overgeneralization and interference strongly based on the principles of error anticipation (cf. Yazdani 1988, Schwind 1988, Catt 1988): Rather tiny context free grammars are enhanced by some additional rules which describe selected faulty structures and invoke error messages zf they are needed for a successful parse. The efforts required to compile an at least approximatively comprehensive rule set even for simple domains of grammar are considerable. Deszdes this, it is the student's risk to fall into the remalninq ~ap of neglected possibilities which seems to be difficult to avoid. Hopefully, an improvemeat of this situation can be achieved by an application of model-based reasoning procedures, where an internal model (of language correctness) is used to simulate and evaluate error hypotheses by investigating their consequences for other parts of the mode\]. To a certain degree the diagnostic results are logically determined by the correct remainder of the utterance and useful results require a balanced ratio between correct and incorrect language use within the solutlon of the student.</Paragraph>
    <Paragraph position="1"> Provided a correct and covering model can be supplied for a limited domain, diagnosis is guaranteed to be precise and robust enouqh and error anticipation eventually may be renounced completely. In order to yield an efficient implementation of the idea into a practical solution a preponderantly data driven procedure instead of a strictly hypotheses driven one seems to be desirable.</Paragraph>
    <Paragraph position="2"> A procedure of this kind }\]as been successfully pursued in an earlier paper on the diagnosis of agreement errors in fixed syntactic environments (Menzel 1988). Quite naturally this success raises the question on how much of the experience gathered can be transferred to other types of grammatical regularities as linear ordering principles or dominance regularities, for instance.</Paragraph>
    <Paragraph position="3"> Up to now the only notable exception to the one-sided orientation on error anticipation has been a fail-soft technique implemented in the error sensitive parsing system Linger (Barehan etal. 1986), an approach which later has been named &amp;quot;word soup heuristics&amp;quot; by their authors: Whenever the normal parsing process based on a principally anticipation-oriented context-free grammar fails, the system attempts to achieve a successful parse by trying single word form substitutions, insertions, deletions or displacements. Although often being very useful in detecting simple flaws of the student, this heuristics not so infrequently produces rather surprising and sometimes even funny interpretations of the input data. Its main drawback is the basic limitation to only single word form errors. Any extension to the handling of complete constituents, desirable as it may be, seems to be condemned to failure because of efficleney reasons: the whole approach is basically expectation driven and it opens up too vast a search space of possible error hypotheses, where the verification of onl~ a single one is not just a trivial task.</Paragraph>
  </Section>
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