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<Paper uid="J79-1036">
  <Title>Grammatical Compression in Notes and Records: Analysis and Cornputdtion Barbara B. Anderson, Irwin D. J. Bross, and</Title>
  <Section position="3" start_page="0" end_page="116" type="intro">
    <SectionTitle>
ABSTRACT
</SectionTitle>
    <Paragraph position="0"> With the exception of pranomial reference, little, has been written (in the field of computational linguistics) about the phenomenon of reference in natural language. This paper investigates the power and use of reference in natural language. and the problems involved in its resolution.</Paragraph>
    <Paragraph position="1"> An algorithm is sketched for accomplishing reference resolution using a notion of cross-sentential focus, a mechanism for hypothesizing all possible contextual references, and a judgment mechanism for dis ~rirninati ng among the hypotheses.</Paragraph>
    <Paragraph position="2"> The reference resolution problem The present work began as an attempt to develop a set of algorithms and/or heurietics to enable a primitive-based, inference driven model of a natural language user (Schank 1972 Rieger 1974) to properly resolve pronomial references acmee eentence bmndaries.</Paragraph>
    <Paragraph position="3"> The authors quickly realized, however, that the problem of pronomial reference resolution is only a .small aspect of a problem which might be termed nominal reference resolution, itself but a 8-11 aspect of the problem 'of the coherence of d text, (or conversation) i, em the manner in which it llmeansu more than the logicd conjunction of the meaningp of its individual constituent aentences, Examples of tqe first problem, i. e. pronomial reference resohtion are given in sentence sequences 1-4 below.</Paragraph>
    <Paragraph position="4">  1. Yesterday some boys from our village chased a pack of wild dogs; the largest one fell into a ditch.</Paragraph>
    <Paragraph position="5"> 2. The wild dogs which forage just outside our village suffer from a strange bone-wealeining disealte. Yesterday some boys from our village chased a pack of wild dogs* the largeat one broke a leg and fell into a ditch.</Paragraph>
    <Paragraph position="6"> 3. Yesterday John chased Bill half a block; he was soon out of breath. 4. My friend Bill has an extremely severe case of asthma. Yesterday  John chased Bill half a block; he was soon out of breath.</Paragraph>
    <Paragraph position="7"> The ~roblem in utterance (text, conversation etc. ) excerpts of the above type is #hat of determining the referents of We various occurrences of the pronouns I' one, I' and &amp;quot;heN For the moment we simply note that usually preferred referents of the two occurreqces of llonell are I1boyl1 and Ild~g~~, (examples 1 and 2 respectively) and those of the two occurrehces of &amp;quot;hew are I1Johnl1 and Bill (exampies 3 and 4 respectively. ) The more general pr~blem of nominal reference resolution is exhibited in EUhe following annotated excerpt from a recent newpaper article (N. Y. Times 7/15/75, byline Arnold Lubasch); subscripted bracketing of the excerpt is intended only to enable later reference to specific parts of the text.</Paragraph>
    <Paragraph position="8">  constitutional challenge by three State As sembly candidates last year threw out [ [the ' code' s] prohibition against attacking any political  misrepresentation of a candidate1 a party affiliation, position on political issues and personal qualifications, including the use af llcharacter defamationr1 and scurrilous attacks. Ill9 Accordbg to [the caurt1s]12 38-page decision, written by  P. hdoore, and Mark A. Con~tanting]~~. 15[ 16[the provisions ba~hg  misrepresentation Irca st a substantial chill on the expres sion of protected speech that are unconstitutionally overbroad and vague. l1 If newpaper reporters had a bit more sympathy for those of us concerned with natu-1 language poocessing, the above excerpt might have read as follows: The state has a Fair Campaign Code.</Paragraph>
    <Paragraph position="9"> Some of the major provisions of the state's Fair Campagin Code are provisions which restrict something.</Paragraph>
    <Paragraph position="10"> Some of the things restricted by some of the major provisions of the state's Fair Campaign Code which restrict something are activities having to do with election campaigning.</Paragraph>
    <Paragraph position="11"> Same of the activities having to do with election campaigning which are restricted by some of the major ,provisions of the state's Fair Campaign Code whioh restrict something are attacking a political candidate's race, sex, religions or ethnic background and misrepresenting a) candidate1 s party affiliation, position on political is sue s . . . Last year three state assembly canddiates filed a constihtional challenge to some of the major provisions of the state's Fair Campaign Code which restrict something.</Paragraph>
    <Paragraph position="12"> Y esterday a special Federal court declared unconstitutional thou of the major provisione of the state's Fair Campaign Code which restrict . something . . , The p&amp; is that in order for a machine or a human to validly claim to have Ilunder~tood~~ the original excerpt&amp; helshelit must be able at the very least to dekonstrate that he/she/it has established the following relationships between various items occurring in the excerpt. (Iqtegers aprbsent subscripted bracketed regments of the original excerpt. )  (f) The identity of 2, 7, and 11 (ii) The identity of 3, 5, 8, and 12 (iii) The fact that 4, 6, 9, and 15 are elements, subsets or pafb of 1 (iv) The fact that 13 and 14 are members of 3  and on and on and on. (I. em a closer analysis of the original excerpt reveals many more relationships which must be established before llundeirstandingu may be clamed. ) It people sctually wrotelspoke in the style of the somewhat facetious paraphrase of the original excerpt, the nominal reference problem would be reduced to one of matching lexcial patterns and recognising a few syntactic cues; to state the obvious, the necessity for more* succinct linguistic communication has forced the development of elliptical devices which shia the burden of nominal reference resolution from syntactic analysis to an analysis of the Hsemanticsll of sentences in context. More specifically, nominal references cannot in general be resolved without the use of general semantic infarmation as well as specific world knowledge.</Paragraph>
    <Paragraph position="13"> While the fact that syntactic a-lysis alone is insufficient for understmding is anything but novel, the question of the magnitude of the nominal reference problem and of its solution1 s crucial dependence upon local context seems to have been little commented upon.</Paragraph>
    <Paragraph position="14"> (Clark (1975) discussee the problem from a viewpoint different from that of this paper, ) The reader who remains unconvinced by the examples above that local context (and specific world knowledge relating to local context) must play a crucial role in reference resolution is asked to consider the two sentence sequences 5a, 6, and 5b, 6.</Paragraph>
    <Paragraph position="15"> 5.</Paragraph>
    <Paragraph position="16"> a. The founding fathers had a difficult time agreeing on how the basic laws governing our country should be framed.</Paragraph>
    <Paragraph position="17"> b. Those foolish people at the country club have spent an incredible amount of time arguing about club rules.</Paragraph>
    <Paragraph position="18"> 6. The second article of the constitution, for example, was argued about for months before agreement was reached.</Paragraph>
    <Paragraph position="19"> In sentence sequence 5a, 6, Itthe second articlett clearly refers to the second article of the constitution of the United States, while in sentence sequence 5b, 6, the reference is to the second article of the constitution of the country club. In each case the only factor involved in resolving the reference is the semantic content of its 10-1 aontextin this case the meaning of the sentende preceding the one in which tke reference occurs.</Paragraph>
    <Paragraph position="20"> Since the lexical item Itthe constitutiontt appears in the example just considered, a word- concerning such proper-noun-like objects is in order. In any language EUhere are lexical Items and phrases such as those appearing in 7 below, which, in the absence of compelling alternative, have standard default ref erentsf for example the standard default referents of the items in 7 are the corresponding items in 8  7. a. The constitution b. The founding fathers c. Wall Street d. The establishment e. The presiaent f. Madison Avenue 8. a. The constitution of the U. S.</Paragraph>
    <Paragraph position="21"> b. The flhnding fathers of the U. S.</Paragraph>
    <Paragraph position="22"> C. The U. S. business. community (or that part of it residing in New Yotk City. ) d. Those people who have the power to influence the course of events  in the nation etc. etc.</Paragraph>
    <Paragraph position="23"> e. The president of the U. S.</Paragraph>
    <Paragraph position="24"> f. The advertising industry.</Paragraph>
    <Paragraph position="25"> In order for textual occurrm-ce of such proper-noun-like objects to be properly handled, their standard default referents must be listed in the lexicon. This is not to say that occurrences of proper-noun-like objects cannot be references to objects occurring previously in the text; rather  it is the case that their default options must also be considered as possible referents.</Paragraph>
    <Paragraph position="26"> As final examples of the reference resolution problem let us consider sentence sequences 9 and 10 below.</Paragraph>
    <Paragraph position="27"> 9. The president was shot while riding in a motorcade down one of the major boulevards of Dallas yesterday; it caused a panic on Wall Street.</Paragraph>
    <Paragraph position="28"> 10. John was invited to tea at the Quimbyls last Saturday; he would have loveq to go, but he knew held be busy then.</Paragraph>
    <Paragraph position="29"> In example 9, while t&amp;e first sentence of the eequence contains a number of noun objects (president, motorcade, boulevards, Dallas) which are potential referents for the occurrence of rlitll in the second sentence, none of the these is in fact, the proper referent; rather, the proper referent of Ifitlt is the event (or fact) that &amp;quot;The president was shot while . . . .</Paragraph>
    <Paragraph position="30"> It In example 10 we have an instance of an adverbial reference (&amp;quot;thenf1) which must be recognized as referring to flyesterday&amp;quot; rather than bo some non adverbial object occurring in the first sentence of that example, Sketch of a Solution Frsm the point of view of computer implementation, the problem of nominal reference resolution is one of creating tokens for noun objects mentioned in a text, and discovering and encoding the relations, alluded to in the text, which hold between them and various other tokens in memory.</Paragraph>
    <Paragraph position="31"> This problem, though certainly not it s magnitude or ramifications, was noticed by Rieger (1974) in his poineering implementation of a primitive-based model of a natural language user. Riegerls system, however, suffers from the incredible inefficiency r esuIting from its need to search all of memory in order to attempt any reference resolution; in addition it will often miss a quite obvious referent entirely, and, in fact, resolves non-pronomial references only accidentally if at all. Before presenting a sketch of a proposed solution to the nominal reference resolution problem, it would be well to detail more precisely the overall language processing enviornment within which it is meint to operate and of which it is a most necessary part.</Paragraph>
    <Paragraph position="32"> First, we adsume that a relatively small set, S, of semantic primitives and $ logical-calculus -like language, L, for expressing ltmeaningsll are available. The set S and language L must satisfy the following two conditions.</Paragraph>
    <Paragraph position="33"> (i) The predicate, function, and constant eymbols of L are members of S.</Paragraph>
    <Paragraph position="34"> (ii) There is a one-to-o* mapping from meanings of (natural language) sentences to formulas of L.</Paragraph>
    <Paragraph position="35"> While a set of prkiitives and a meaning representation language even demonstably close to satisfying the above conditions have yet to be produced, we will, in examples to follow, make use of meaning represen tations; the only claim we will make for them is that the functibns served by their constituent constructs must be served by the elements of any adequate system.</Paragraph>
    <Paragraph position="36"> In addition to a meaning representation scheme we will assume en encoding of world knowledge of the sort which a lltypicallt adult might possess, again with the same obvious caveat.</Paragraph>
    <Paragraph position="37"> While the question of translation from natural language sentence8 to'meaning representations will not be touched upon here, we will sasume sentence -by- sentence translation of the sort exhibited in various examples to follow.</Paragraph>
    <Paragraph position="38"> The solution PO the reference resolution problem rests in recognizing the fact that reference is an elliptical device, and +that the human under stander of. natural language cannot recapture that which was elided once he is too far from it in the text; in fact, he cannot resolve a reference to a pint in the text more than a few-sentences back without going back and pondering it (if he can do so at all). We should note that this is true even ih the case in which the referent doesn't actually appear in the text, but appears only in an inference from some statement made in the text. In this latter case - a case which we will discuss only at the very end of this paper the reference is not resolvable (and would not therefore have Been made by the c~eator of the text in the first place). unless the statement from which the inference is made appears shortly before in the text . Though we cannot say precisely how far back is meant by. &amp;quot;shortly before, &amp;quot; it is certainly no more than a few sentences. Fbr a given sentence, S, appearing in a text we will refer to the gequence of sentences preceding S by no more than the intended distance as the focus of S.</Paragraph>
    <Paragraph position="39"> In terms of computer implementation, we will, in the processing of a text (which we conc-eive of as proceeding sentence-by-sentence), maintain the following focus sets.</Paragraph>
    <Paragraph position="40"> %bje CJ' (i) The noun-object focus - the set of tokens of a noun meaning representation~ of the focus of S (where S is the bentence currently.</Paragraph>
    <Paragraph position="41"> being processed) (ii) The event focus -a set aontaining, for every sentence W in the focus of S, the object EVENT(F), where F is the meaninq representation of W, and EVENT is a function which maps the meaning of a formula, F, into a noun-like object whose meaning is &amp;quot;the event (or fact) that F&amp;quot; (iii) The time focus - a set containing taken8 for all time references (e. g, yesterday, five olclock, etc. ) occurring in the meaninq representation of the focus of S.</Paragraph>
    <Paragraph position="42"> The reader may question our inclusion of every object appearing in the meaning xepresentation of the focus of S in one of the above focus sets, i. e. in the set of potential referents. In fact, however, it seems to be the case that any object (of one of the above-mentioned types) occurring in the meaning representation of the focus of S may be the referent of an object occurring later in the meaning representation of S. Sonsidex, for example, the sentence sequences formed by taking each of he sentences af 12 below, - in turn - as an immediate continuation of a text zontaining sentence 1 1 below.</Paragraph>
    <Paragraph position="43">  11. Stan argued with his sister Fran in an attempt to convince her that she should bring Mary, whom he would like to get to knpw, on their planned trip to the San Diego Zoo tomor~ow.</Paragraph>
    <Paragraph position="44"> 12. a. - He was really insistent.</Paragraph>
    <Paragraph position="45"> b. - She was hard to convince.</Paragraph>
    <Paragraph position="46"> C. - It was useless.</Paragraph>
    <Paragraph position="47"> d. He thinks - she's the prettiest one of all Frads friends. e. The prospect really excites him.</Paragraph>
    <Paragraph position="48"> f. He arguecl that - ft wouldn't tie Mary up for more than half a day. g.</Paragraph>
    <Paragraph position="49"> - It's EUhe best one in the country, you know.</Paragraph>
    <Paragraph position="50"> h. - She thruught - it was a twrible idea.</Paragraph>
    <Paragraph position="51"> i.</Paragraph>
    <Paragraph position="52">  She happened to be busy then, but expressed an interest in coming along ahother the.</Paragraph>
    <Paragraph position="53"> Ea&amp; of the mderlined items in sentences 12a-12i references some object in senten- 11.</Paragraph>
    <Paragraph position="54"> (For the sake of clarity we present in 13 below the referents as we understand them, )  13, a, Stan b. Fran c. The attempt (to convince , . .</Paragraph>
    <Paragraph position="55"> d. Mary em EVENT \Stan will get to know Mary) f. The trip g. The San Diego Zoo h. Both --- @he a&amp; it are ambiuous; if - she is taken to be &amp;quot;Fran, l1 then  it refers to EXENT (Fran will bring Mary ,. .); if - she is taken to be &amp;quot;Maryll), then - it refers to EVENT (Mary will come.. . ) The point is, of course, that any item in (the meaning representation of) a sentence, S, may be referenced by some item in (the meaning repr eeentation of) a latter sentence.</Paragraph>
    <Paragraph position="56"> On the other side of the coin the question of identifying potential re- null ferences is just as important as that of identifying the seb of all possible referents for an object which is known to reference something. If we were' concerned only with pronomial referenee reaolution, the problem would have a simple solution; every pronoun is a reference. For nominal items other than pronouns the problem is far less simple; if a noun occurs in a text just how do we know if there is a previously occurring nominal item to which it refers? As much as we would like there to be algorithmically testable criteria, i. e. recognizable syntactic and/or semantic cues, for making the decision, there seem to be none. Thus, the mechanism we propose considers every token appearing in the translation of a sentence as a possible reference. At present, we hypothesize the existence of a small set, R, of relations which are suffvient to account for all instances of nominal reference. Included in this set are, at the very least, the relations identity, member of, subset of, and part of. Noje that although this list of relations im quite small, it suffices to handle all the examples of reference presented thus far (i. e. those occurring in sentence sequences 1-6 and 9-12 as well as those occurring in the excerpted newpaper article above).</Paragraph>
    <Paragraph position="57"> All of the above observations taken together lead to the following sketch of an algorithm for reference resolution.</Paragraph>
    <Paragraph position="58"> I. #AS each new sentence, S, is transrated into its meaning representation, the various focus sets (noun-object, event, time) are updated. 11. A set, H, is formed containing all tuples of t&amp;e form (N1, N2, P) such 'that N1 is a nominal item occurring in(the meaning representation of S, Nz is an object occurring in the focus set (noun-object, event, or time) appropriate to N1 , and is a member of R; H is the set of all current refewnce hypotheses arising-from S. III. A lljudgment mechanism, &amp;quot; discussed below, is invoked to determine the liklihoods of the correctness of the various members of H. It is clear that following step II any further processing of reference hypotheses requires that all members of H be considered relahive to one avther, since the correctness or incorrectness of one may depend crucially upon that of others.</Paragraph>
    <Paragraph position="59"> In the general case not all hypotheses will turn out to be correct, and in fact some may contradict others - for instance in the case of two hypothesis-triples with identical first and second elements and different third elements.</Paragraph>
    <Paragraph position="60"> Once it has been created, the set H is submitted to a &amp;quot;judgment mechanismft whose task it is to choose some of the hypotheses as valid and others as invalid. The judgement mechanism must clearly have access to the world knowledge stored in memory, and must be capable of performing inferencing of a sort which produces decisions as to the relative Eklihoods of the various hypotheses.</Paragraph>
    <Paragraph position="61"> Before giving example8 of just how such a judgment mechanism might work, we should make it clear that our sense of I1inferencing1l is very different from Riegerls (1974). In Riegerls sense inferencing is undirected, while ours is directed toward the goal of validati~g hypotheses. There is, in addition, another sense in which the sort of inferencing to be done by the judgment mechanism is directed. The fact that the rgasons for validating or throwing out a particular reference hypothesis (on the part of human natural language users) involve the information coweyed in local context as well as world knowledge relating to items contained in that information (and world knowledge relating to items contained in world knowledge relating to items contained in that information, ctc. ) constitutes a good guess as to the particular pieces of world kncrwledge and the rules of inference which must be involved in judging that hypothesis. Ekamples of reference resolation 14 and 15 below contain components of possible meaning repfek sentations of the two sentencel of sentence sequence 1 at the beginning of this paper.</Paragraph>
    <Paragraph position="62">  C1A%hGhGAC5AC&amp; and G7hCshCo AC~OAC~~ respectively. Note that we are not claiming that the predicates CHASED, and FALL INTO and the constants YESTERDAY, BOY, DOG, PAST and DITCH are at the leve3. of semantic primitives; rather, the above analyses are at just the level which we need to illustate the operation of the reference resolution mechanism. Further more, the symbols YESTERDAY, BOY, DOG, PAST and DITCH ahould be taken as pointers to the definitions of the appropriate items encoded in memory in whatever fashion. The brackethg in the notation [A], where A is a pointer to a definition, is meant to be a function which takes A into an object whose meaning ie the class of items satisfying the meaning pointed to by A.</Paragraph>
    <Paragraph position="63"> Once the translation of the first sentence of sequence 1 into its meaning representation has been completed - on the assumption that that sentence is at the beginning of the text being processed - the various focus sem will contain the followkg: no.- object focus: [xl, xz) ; event fbcps.: [(cfic21\~/\chcd\~~ )3 ; time focus [YESTERDAY ] .</Paragraph>
    <Paragraph position="64"> After the second sentence is translated the set, H, of reference triple hypotheses presented to the judgment mechanism will then be the following : is a member of is a sqbget of is~part of Note that no member of the event focus occurrs in H because the translation of the second sentence contains no term of the form EVENT(y); for simplicae omit the question of time referencing.</Paragraph>
    <Paragraph position="65"> All of the relations between y2 and xl or rt can be ruled out pn the basis of SUBSET (x,, [DOC]) SUBSET (xl. [BOY]), MEMBER Or,, [DITCH]) and of the world knowledge to the effect that boysldogs cannot be identical to, members of, eubsets of or parts of ditches (of course in some weird fairy tale setting one of these might be possible and shouldn't be thrown out; but in such a case local context would inform us of the &amp;quot;weirdrr situation and the appropriate one wouldn't be thrown out. ) The hypothesis that or y3 is a part of either xl or xz can be  ruled out on the basis of SUBSET (q, [BOY]) and SUBSET (x,, [DOG]), which tell us that q and x2 are sets of objects, and the world knowledge that sets don't have &amp;quot;partsi1 in the sense of the &amp;quot;part of1! relation.</Paragraph>
    <Paragraph position="66"> Identify between yl and either XI or x2 can be ruled out on the basis of MEMBER (yl , y3) which tells us that yl is an ihdividual and SUBSET (x1, [BOY]), SUBSET (x2, [DOG]), GREATER (SIZE (x,), l), and GREATER (SIZE (xz), 11, which tell us that xl and x2 are sets containing more than one object. (Remember that we're not doing axiomatic set theory in which there are no lgindividuals in our sense and in which the sort of ll-iindividualll which is dealt with can be a subset of some set. ) Fmally, the &amp;quot;member of&amp;quot; relation between y3 and either xl or x2 can be ruled out pn the basie of MEMBER (yl, y3) which requires thpt y3 be a set, SUBSET (xl, [BOY]), SUBSET (x, [DOG]), GREATER (SIZE (xl), I), and GREATER (SIZE (x2), 1), which tell us that x1 and x2 are sets containing more thad one element each, and the fact that sets are not members of sets.</Paragraph>
    <Paragraph position="67"> (Again, we're not dealing with set theory; if in fact, we were - talking about axiomatic set theory in English, then local context would contain that information, and aiff erent inferences would come into play. ) This leaves us with the following hypotheses : is identical to '' {is a subset ofj [:j y, is a member of  respectively because of MEMBER (yl, y,).</Paragraph>
    <Paragraph position="68"> At any rate, the judgment mechanism assumes at this point that either yl is a member of xl or yl is a member of x2. The readear is asked to recall at this point that in presenting the usually preferred referents for references in sentence sequences 1-4 the claim was made that in sentence sequence 1, the usually preferred referent for &amp;quot;onefr is lfboys.&amp;quot; The reason for this claim is the authort s observation. that, when such a pronomial refercnce occurs as the surface subject of a sentence, in the absence of semantic content which discrminates among the various possible referents, most people seem to take the eurface subject of the last sentence in the focus as the inbnded referent. The reason for this human judgment is probably that the readerlhearer takes the surface subject to be the &amp;quot;topicll of a sentence. If this observation is correct, the judgment mechanism should, in the current example, simply choose &amp;quot;one of the boysr1 (yl is a member of xl) as the proper referent. If this observation is incorrect, the judgment mechaaism should judge that there is ambiguity in the reference 'lone Sentence sequence 2 at the beginning of this paper would be handled in precisely the same manner as sentence sequence 1 up to the point at which 11y3 is a member of xl1I and &amp;quot;y, is a member of x,&amp;quot; were the remaining hypotheses. The knowledge that Ifthe dogsLt refer red to suffer from a strange bone -weakening diaease would bhen cause the judgment mechaniam to strengthen the likelihood that tlonell refers to &amp;quot;dogs, thus causing Ityl is a member of x,&amp;quot; to be the preferred judgment. Sentence sequence16 below contains an example of EVENT reference. 16.</Paragraph>
    <Paragraph position="69"> The presidnet was shot yesterday. It caused a panic on Wall Street. Omitting all other details of the translation into meaning representation we simply note that the primitive -level predicate into which cause&amp;quot; is tranqlated requires an object of the form EVENT (F) as its subject (i. e. if we say something like &amp;quot;John caused a stir&amp;quot; what we mean is that John did something and the event (or fact) that he did that caused a stir.) Thus, when the 2nd sentence is handled, the only possible referents for will be the objects contained in the EVENT focus, namely just EVENT (the president was shot yesterrlay). The judgment mechanism thus must skply decide if the event (or fact) that the president was shot yesterday was likely to have caused a panic on Wall Street, a judgment which, with adequate world knowledge, should certainly be confirmed.</Paragraph>
    <Paragraph position="70"> Sentence sequence 17 is a very similar case.</Paragraph>
    <Paragraph position="71"> 17. The president was shot yesterday. Bill told me all about it. It caused a panic on Wall Street.</Paragraph>
    <Paragraph position="72"> In order to resolve the reference 'lit&amp;quot; in the last sentence of 17, the judgment mechanism would have to decide on the relative likelihoods of i and ii below (i) The event (or fact) that the president was shot yesterday caused a panic on Wall Street.</Paragraph>
    <Paragraph position="73"> (ii) The event (ok fact) that Bill told me about the president being shot yesterday cauaed a panic on Wall Street.</Paragraph>
    <Paragraph position="74"> Again, with the availability of reasonable world knowledge about such things as presidents, their being shot and panics, the judgment mechanism should be able to choose the proper referent for &amp;quot;it1I While a fully detailed specification of the judgment mechanism must await further investigation, the above examples should illustrate, at least in part, the manner in which we conceive of its operation.</Paragraph>
    <Paragraph position="75"> Conclusions The phenomenon with which we have been dealing is one example of what we would like to call the llcreativefl aspect of language use; more specifically, reference of the sort we have described - and attempted to handle - is an elliptical device necessary for effective communication; moreover, it is a device which exhibits the ability of language to &amp;quot;change the ground rulestf in a very flexible and fluid manner in response to context.</Paragraph>
    <Paragraph position="76"> At this point we must admit that there is an even more creative type of reference than the sort we have dealt with. 18 below is an example of this type of reference.</Paragraph>
    <Paragraph position="77"> 18. Last week I caught a cold while vieiting my mother in Chicago; as ueual , the chicken eoup had too much pepper in it.</Paragraph>
    <Paragraph position="78"> The interesting reference in the above example is ILchickeh soup. There is no item in the first sentence to which it is directly related; on the other hand, few people have any trouble resolving it by interpolating between the two sentences of example 18 the idea expressed in sentence 19 below: 1,q. When I get sick my mother makes me chicken soup.</Paragraph>
    <Paragraph position="79"> If sentence 19 were available, our reference resolution mechanism would easily come up with an identity relation between the two occurrences of It chicken eoup Obviously, for our proposed mechanism to resolve this reference, some sort of inferencing must first work on the 1st sentence of 18 to produce the meaning of 19 as an inference. Thus it is clear that reference resolution and general inferencing must be inter leaved. null The mechanism proposed abave does not handle the entire problem. It does, however, seem to be a minimal model of reference resoIdtion (minimal in the sense that at least this much must be going on). In addition, it provides for that control over the use of general inferencing which is required to avoid a combinatbrial explosion (BOOM).</Paragraph>
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