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<Paper uid="C94-1080">
  <Title>CONCURRENT LEXICALIZED DEPENDENCY PARSING: A BEHAVIORAL VIEW ON ParseTalk EVENTS</Title>
  <Section position="8" start_page="492" end_page="492" type="concl">
    <SectionTitle>
6 CONCLUSIONS
</SectionTitle>
    <Paragraph position="0"> The ParseTalk model of natural language understanding aims at the integration of a lexically distributed, dependency-I)ased grammar Sl)CCification with a solid formal foundation for concurrent, object-oriented parsing. The associated concurrent compu~ttion model is based el} the actor paradigm of object-oriented programming, with several extensions relating to special reqtfirements of natural langtmge processing. These cover mechanisms for complex message distribution, synchronization in terms of request-reply protocols, and the distinction of dislriht, tion and computation events. We have shown how the semantic specification of actor systems can be used for the consideration of global interrelatious of word actors at the grammar level (event type networks) and the parser level (event networks). While event type networks provide a general, global view on the behavioral aspects of ottr grannnar specification, the current formalism slill lacks the ability to stlPi)ort retinal reasoning about computational prope, rties of distributed systems, such as deadlock freeness, termination. On tim oflmr hand, event networks illustrate the contimtations during real parses, but do not allow predictions in general cases. Providing a type discipline for actor detinitions may Ix: a reasonable apl)roach to till the methodological gap between both layers of description.</Paragraph>
    <Paragraph position="1"> The ParseT?flk model has been exlmritnentally vali..</Paragraph>
    <Paragraph position="2"> dated by a prototype system, a parser for Germ;re. The current fifll-form lexicon contains a hierarchy of 54 word-class specifications and nearly 1000 lexieal entries; a module for lnorphological analysis is trader development. The parser's coverage is currently restricted to the analysis of assertional sentences, with focus on complex noun and prepositional phrases. The Parse'l?flk system is impleinented in Smalltalk, with extensions that allow for coarse-grained parallelism through physic,'d distribution in a workstation cluster (Xu, 1993) and asynchronous ntessage passing. It is loosely coupled with lhe l.OOM knowledge representation system (MacGregor &amp; Bates, 1987). We currently use a knowledge base with 120 concept delini}ions covering the domain of information technology. Furthennore, an interactive graphical grammar/parser engineering workbench is supplied which supports the development and maintenance of the ParseTalk grammar sysleln. null</Paragraph>
  </Section>
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