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<Paper uid="M92-1038">
  <Title>University of Massachusetts : Description of the CIRCUS System a s Used for MUC-4</Title>
  <Section position="3" start_page="283" end_page="284" type="intro">
    <SectionTitle>
INCIDENT
DATE =NIL
LOCATION =NIL
</SectionTitle>
    <Paragraph position="0"> and the victim description is added to the victim stack.</Paragraph>
    <Paragraph position="1"> S2: (we omit this sentence from the discussion - no alterations to memory are made ) S3: (GARCIA ALVARADO &gt;CO &amp;&amp;56 &gt;CO WAS KILLED WHEN A BOMB PLACED BY URBAN GUERRILLAS ON HIS VEHICLE )XPLODED AS IT CAME TO A HALT AT AN INTERSECTION IN DOWNTOWN SAN SALVADOR &gt;PE) CIRCUS generates 5 CNs in response to this sentence. A simple CN describing a weapon is generated b y &amp;quot;BOMB.&amp;quot; More complicated CNs are triggered by &amp;quot;KILLED,&amp;quot; &amp;quot;PLACED,&amp;quot; and &amp;quot;EXPLODED .&amp;quot;  The trigger &amp;quot;KILLED&amp;quot; creates a murder CN with victim = &amp;quot;GARCIA ALVARADO.&amp;quot; The trigger &amp;quot;PLACED&amp;quot; creates a location CN with instrument = &amp;quot;BOMB,&amp;quot; and actor = &amp;quot;URBA N GUERRILLAS.&amp;quot; This same CN also looks for a physical target inside a prepositional phrase, but it misses &amp;quot;ON HIS VEHICLE&amp;quot; because &amp;quot;on&amp;quot; is not one of the prepositions that it predicts . If the sentence had said &amp;quot;outside &amp;quot;, &amp;quot;inside&amp;quot;, &amp;quot;by&amp;quot;, &amp;quot;near&amp;quot;, &amp;quot;in&amp;quot;, &amp;quot;under&amp;quot;, &amp;quot;opposite&amp;quot;, &amp;quot;across_from&amp;quot;, or &amp;quot;in_front_of', instead of &amp;quot;on&amp;quot;, we would have  picked up this physical target. The omission of &amp;quot;on&amp;quot; was a simple oversight in an otherwise legitimate CN definition. This particular CN is specifically predicting a bomb since bombs are frequently the object of the verb &amp;quot;t o place&amp;quot; in this domain.</Paragraph>
    <Paragraph position="2"> The trigger &amp;quot;EXPLODED&amp;quot; creates a bombing CN with instrument = &amp;quot;A BOMB .&amp;quot; Note that we miss the location San Salvador in S3. Although we have a bottom-up mechanism designed to find dates and locations, it doesn't always work. All 5 CNs are placed in a single partition which generates a new incident structure containing a single subevent:  target/victim descriptions, and determines that this new subevent is compatible with the incident structure already i n memory. MBC therefore merges the two incidents, and memory acquires the fact that Alvarado was killed by a bomb.</Paragraph>
    <Paragraph position="3"> S4-7: (we omit these sentences from the discussion - no alterations to memory are made ) S8: (VICE PRESIDENT--ELECT FRANCISCO MERINO SAID THAT WHEN THE ATTORNEY @GENERAL@S CAR STOPPE D</Paragraph>
  </Section>
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