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<Paper uid="C92-1058">
  <Title>The Primordial Soup Algorithm A Systematic Approach to the Specification of Parallel Parsers</Title>
  <Section position="3" start_page="0" end_page="0" type="intro">
    <SectionTitle>
1 Introduction
</SectionTitle>
    <Paragraph position="0"> In this paper we present a general framework for parallel parsing algorithms. Parsing ean be seen ms a process in which a set of partial parse trees is recognized. One starts with the productions as elementary trees. Small trees Cml be combined into larger trees, yielding ew~.r larger and larger structures, until completed parses for a particular target sentence are produced. We envisage the set of recognized trees as a kind of primordial soup. Small trees float around and if they fit together they can be combined into a larger tree. This is, in a nutshell, the Primordial Sotq) paradigm.</Paragraph>
    <Paragraph position="1"> In the most general approach, trees can combine in arbitrary ways. That is, a new tree can be created from two existing trees if there is a partiaI overlap between the trees. The overlapping part is unified. Tree creation is nondestructive, in tim sense that a tree can be used more than once for the production of a larger tree. Or, t(~ put it in a different way, the initial soup contains an abundant amount of raw material. Thus all relevant trees can actually be created.</Paragraph>
    <Paragraph position="2"> The Primordial Soup Algorithm can be relined into a variety of parsing strategies by adding constraints, either on the allowed type of trees or on the way in which existing trees ean be combined. A parsing strategy specifies which trees will be recognizerl, without bothering to specify control and data structures that must be added in order to arrive at practical implementations. null For the development of parallel implementations, the (initial) absence of control structure is &amp;n :-:u'~sC/?l;~ a~'~ decisions about system architecture can be deferred to a later stage when the strategy has been fleshed out in more detail. Our specification of the Primordial Soup Algorithm allows for a systematic derivation of implementations of parsing strategies as is shown in a more detailed technical report \[JPSZ\]. These derivations are em'ried out within a partial order framework as introduced in \[JPZ\]. In the restricted space available here we concentrate on the Primordial Soup Algorithm ~ a fi'amework for the specification of parsing strategies.</Paragraph>
    <Paragraph position="3"> In section 2 the l'rimordial Soup Algorithm is introduced, exemplified by a CYK-like approach.</Paragraph>
    <Paragraph position="4"> \[n section 3, t.im formalism is slightly extended so ~ to allow for the description of almost any parallel or sequential parser.</Paragraph>
  </Section>
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