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<Paper uid="C82-2065">
  <Title>LESK: A LANGUAGE SYNT~TIZING NATURAL LANGUAGE, COMPUTER LANGUAGE AND LOGIC</Title>
  <Section position="2" start_page="0" end_page="0" type="intro">
    <SectionTitle>
Introduction
LESK (Language for Exactly 3tatl~ Knowledge) is intend-
</SectionTitle>
    <Paragraph position="0"> ed to bridge the considerable gap between natural language (I~L), computer lan6uage (CL) and log~tc. It is desirable to do so for the following reason. To implement any non-trivial computer system for some problem domain, one must first have a very clear understanding of the domain concepts. Usually the implementors do not have this knowledge, and must struggle to obtain it from the domain experts, who are usually not computer experts. Hence a means of precise and efficient knowledge expression would be very useful. No such tool exists today and we therefore seek to develop one. LESK is a first approximation to such a medium for knowledge capture.</Paragraph>
    <Paragraph position="1"> Anyone who has participated in the design of any system where knowledge transfer from experts was involved will appre -~ clare the need for such a tool. The existlng tools are the following: ~L, mathematical concepts and notation, computer concepts and notation, plus assorted devices llke dls4~ams, plctures, models, etc. By far the major tool is NL however, which is unfortunately very poorly used by most paople, particularly recent university @~aduates. The most frequent ezTors include the use of undefined termlnolo@~, synonyms or homon~ns (whose status as such must be guessed), unclear syntax, logical - 262 errors (such as outright contradictions), undefined relations between concepts, and sPSmp~e lack of good organizationdeg LESK forces the user to express him/herself izi ways designed to minimize such errors. A T RSK system (an interactive program whPSch &amp;quot;understands&amp;quot; LESK) would further reduce such errorso Criteria for LESK LESK should a) be readable by most university graduates in science, medicine, law or business, for ezmnple| b) be writable by most people with a basic knowledge of set theory, logic end computers'; o) have a simple semantics expressible in first-order logic~ d) be lmplementable using artificial intelligence techniques! e) be sufficiently general to be usable in the subjects of interest to those listed in a).</Paragraph>
    <Paragraph position="2"> The present design of LESK has been shown to meet all of these criteria.</Paragraph>
    <Paragraph position="3"> ~asi~n of ~sK LESK should be viewed as a language for making assertions about sets, tuples, sequences, functions, relations, procedures and other s~nple mathematical concepts using an Enslish-like syntax (many other NLs could be used! translation of LESK-based knowledge should be easier than translation of NL). The user declares words or phrases either explicitly or ~nplioitly to be nouns (or noun-like), adjectives, prepositions, or verbs (other categories have not been necessary). Nouns and noun phrases denote sets, stative verbs denote relations, action verbs denote procedures, and prepositions denote case relations. The syntax is a compromise between b-L, CT, and logo. All constructs have a simple f~rst-order logic interpretation.</Paragraph>
    <Paragraph position="4"> An example (whose spirit should warm the heart of those who despair of ever understanding the regulations of their - 263 institution) follows. LESK primitives are in lower case. We first illustrate ~oun deo!arations. (N.B. In the final paper, this example will be greatly expanded and explained.)  every PERSON: - has I NAME - has I integer called their AGE - has I ADDRESS end, every STUDENT: kinds: IK;LL-TIHE -, PART-TIME - | kinds: UNDERGRADUATE -, GRADUATE--! - is a PERSON! - is ENROLTR~ IN I DEGREE PROGRAM! - is a STUDENT IN 1 FACULTY, SCHOOL or DEPARTMeNt! - has 1 ACADEMIC RECORD end.</Paragraph>
    <Paragraph position="5"> every ACADEMIC RECORD of a STUDENT X: - has 1 FACULTY, SCHOOL or DE~T! - has 0 or more COURSE CREDITS! - has 0 or more COURSE SECTIONS called the COURSES-BEING-TAKEN BY X end * every COURSE CREDIT: - is a pair~X, Y~ where X is a COURSE,  Y is a LETTER GRADE end, We illustrate next two stative verb declarations: a STUDENT X is ENROLLED IN a COURSE SECTION Y iff-X is on the ENROLLMENT LIST of Y.</Paragraph>
    <Paragraph position="6"> a STUDENT X is a STUDENT IN a FACULTY, SCHOOL or DEPARTMENT Y if f: - 264 Y= - the FACULTY, SCHOOL or DEPARTMENT of the ACADEMIC RECORD of X.</Paragraph>
    <Paragraph position="7"> Finally, we illustrate an action verb declaration: To ENROLL a STUDENT X IN a COURSE SECTION Ys preconds for each PREREQUISITE Z of Y there is a COURSE CREDIT ~Z,M&gt; on the ACADEMIC RECORD of X such that M is a PASSING GRADE~ X has PAID the FEE of Y| adds negate s delete: procedure: add X to the ENROLLMENT LIST of Y! add Y to the COURSESBEINGTAKEN BY X end.</Paragraph>
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