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<Paper uid="C82-2022">
  <Title>REVISING AN ATN PARSER</Title>
  <Section position="1" start_page="0" end_page="0" type="abstr">
    <SectionTitle>
REVISING AN ATN PARSER
</SectionTitle>
    <Paragraph position="0"> tested in a series of experiments on complex sentences taken from narrative texts (1,2,3,4). The construction of a complex graemmz as well as the results of our experiments showed some limits and inadequacies of Woods&amp;quot; ATN as it stands (11), especially when used to parse Italian, a relatively freeorder language with a well developed morphological system.</Paragraph>
    <Paragraph position="1"> 1.1. &amp;quot;Parameter-passing&amp;quot; actions such as SENDR and LIFTR have been often Judged &amp;quot;dirty&amp;quot; operations under a formal view-point. Moreover it is almost impossible to keep the control of the cross-level pa~sed information, unless the ~umber of registers is increased. Such an increase is otherwise unmotivated. This difficulty is more evident in Italian relative clauses such as: L&amp;quot; uomo la cui crudelta&amp;quot; tutti conoseiamo The man (the) whose cruelty everyone knows L&amp;quot; uomo la crudelta&amp;quot; del quale tutti conoscismo The man the cruelty of whom everyone knows L deg uomo del desiderio di vendetta del quale ti he parlato The man about the desire for revenge of whom I spoke to you in which a very heavy use of such actions, as well as of flags, is required. These phenomena, together with the richness of morphological inflexion, increase the necessity for morphological and morpho-syntactic short, long-distance and cross-level tests.</Paragraph>
    <Paragraph position="2"> - I01 1.2, Another problem is proposed by the structural ambi8~ity of sequences of PP's, for which both the &amp;quot;embedding&amp;quot; and the &amp;quot;same-level&amp;quot; hypotheses are presented! a sentence with ) PP's has 5 parses accordlng to the schema</Paragraph>
    <Paragraph position="4"> An attempt to limit th~s explosion was made by adding oertaln.</Paragraph>
    <Paragraph position="5"> functional labels depending upon the verb frame. This experiment showed that attention should be focussed on developing an adequate system of functional tests.</Paragraph>
    <Paragraph position="6"> 1.3. A statistically based, dynsmic heuristic mechanism has been put to work in the traversal of the network. Those paths which have been more frequently traversed in previous parsed frasments of a given text are attempted first, during the analysis of the CUZTent sentence (6).</Paragraph>
    <Paragraph position="7"> In this way, the concept of performance based syntactic expectation has been introduced and tested. It appeared that ATN is very suited to the introduction of heuristic techniques and also that these techniques should include a scheduling procedure based on arc types (10).</Paragraph>
    <Paragraph position="8"> 2. A revision of the linguistic formalism as well as of the parsing alSorithm is now in progress, and should take all these considerations into account. Furthermore, those linsuistio phenomena related to conversation such as anaphora and the analysis of partial and partially correct input must be taken into account in the desis~ing of the formalism and the ATN actions and forms, not only for applicative purposes, but above all in order to enlarge the range of phenomena to be included in a ~ammar.</Paragraph>
    <Paragraph position="9"> 2.1. The parser relies both on structural and functional Information (7), i,e. a limited collection of surface structures and functional labels. A set of fixed (control) pattsz~s might also be included in this static syntactic knowledge</Paragraph>
    <Paragraph position="11"> the general structure of the algorithm* Storing and retrieving will be modified, in accordance with our observations in 1.1. A single register external to the levels of computation will be progressively set to the results of the analysis during parsing. Access to precise location of this structure is guaranteed by the functional labels. Traditional ATN registers can be locally used for special purposes. A detailed description of our whole mechanism including examples will be given* Already assigned functional labels cannot be chanEed! left concatenation of them has been preferred (8). A mechanism has also been provided to move pointers from constituents to gape or anaphorical pronouns (inside the sentence borders) (5). This is an attempt to treat by a uniform action or sequence of actions equ/-NP deletion, gapplng, coordination.</Paragraph>
    <Paragraph position="12"> 2.3. Some local procedures connected with the lexicon have been added to these mechanisms. These procedures include the transmission of feature's to higher level nodes in the structure, the proceduralisation of idiosyncrasies of single leKical entries and &amp;quot;paraphrase'. The latter is expected to reduce nominalizatlon to the corresponding verb with its frame components and to account for linguistic units which have identical distribution and syntactic behavlour.</Paragraph>
    <Paragraph position="13"> 2.4* The present list of &amp;quot;linguistically* motivated processes is open-ended, as we are now trying to identify others, which can be considered to be linguistic (procedural) degum/versals &amp;quot;*</Paragraph>
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