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<Paper uid="A97-1021">
  <Title>Large-Scale Acquisition of LCS-Based Lexicons for Foreign Language Tutoring</Title>
  <Section position="3" start_page="139" end_page="140" type="intro">
    <SectionTitle>
2 Application of the LCS
Representation to FLT
</SectionTitle>
    <Paragraph position="0"> One of the types of knowledge that must be captured in FLT is linguistic knowledge at the level of the lexicon, which covers a wide range of information types such as verbal subcategorization for events (e.g., that a transitive verb such as hit occurs with an object noun phrase), featural information (e.g., that the direct object of a verb such as frighlen is animate), thematic information (e.g., that Mary is the agent in Mary hie the ball), and lexical-semantic information (e.g., spatial verbs such as throw are conceptually distinct fi'om verbs of possession such as give). By modularizing the lexicon, we treat each information type separately, thus allowing us to vary the degree of dependence on each level so that we can address the question of how much knowledge is necessary for the success of the particular NLP application. null This section describes the use of the LCS representation in a question-answering component of the MILT system (Sains, 1993; Weinberg et al., 1995).</Paragraph>
    <Paragraph position="1"> As described above, the LCS representation is used as the basis of matching routines for assessing students' answers to free response questions about a short foreign language passage. In order to inform the student whether a question has been answered  Jack threw the book in the trash Jack threw the book in the trash exact match &amp;quot;That's right&amp;quot; Jack put the book in the trash Jack threw the book in the trash missing MANNER &amp;quot;How?&amp;quot; .Jack threw the book in the trash Jack put the book in the trash extra MANNER &amp;quot;You're assuming things&amp;quot; .Jack is friendly Jack put the book in the trash mismatch primitive &amp;quot;Please reread&amp;quot; Jack threw the book Jack put the book in the trash missing argument &amp;quot;Where?&amp;quot; correctly, the author of the lesson must provide the desired response in advance. The system parses and semantically analyzes the author's response into a corresponding LCS representation which is then pre-stored in a database of possible responses. Once the question answering lesson is activated, each of the student's responses is parsed and semantically analyzed into a LCS representation which is checked for a match against the corresponding prestored LCS representation. The student is then informed as to whether the question has been answered correctly depending on how closely the student's response LCS matches the author's prestored LCS.</Paragraph>
    <Paragraph position="2"> Consider what happens in a lesson if the author has specified that a correct answer to the question Addnde paso Jack el libro? in Spanish is Jack fir6 el libro a la basura ('Jack threw out the book into the trash'). This answer is processed by the system to produce the following LCS:  The LCS is stored by the tutor and then later matched against the student's answer. If the student types Jack movio ' el libro de la mesa a la basura ('Jack moved the book froln the table to the trash'), the system must determine if these two match. The student's sentence is processed and the following LCS structure is produced:  (2) \[E .... CAUSE  The system identifies the student's response as a match with the prestored answer, but it also recognizes that there is one piece of missing information and one piece of extra information.</Paragraph>
    <Paragraph position="3"> The &amp;quot;Missing&amp;quot; and &amp;quot;Extra&amp;quot; output is internal to the NLP component of the Tutor, i.e., this is not the final response displayed to the student. The system must convert, this information into meaningful feedback so that the student knows how to repair the answer that was originally given. For example, the instructor can program the tutor to notify the student about the omitted information in the form of a 'How' question, or it can choose to ignore it.</Paragraph>
    <Paragraph position="4"> The extra information is generally ignored, although it is recorded in case the instructor decides to program the system to notify the student about this as well. The full range of feedback is not presented here. Some possibilities are summarized (in English) in Table 1 (adapted from (Holland, 1994)). Note that. the main advantage of using the LCS is that it allows the author to type in an answer that is general enough to match any number of additional answers.</Paragraph>
  </Section>
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