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<?xml version="1.0" standalone="yes"?> <Paper uid="C92-2073"> <Title>HOW TO VISUALIZE TIME, TENSE AND ASPECT? COMMENT VISUALISER LE TEMPS ET L'ASPECT ?</Title> <Section position="3" start_page="0" end_page="0" type="metho"> <SectionTitle> 3 For the time being only the first and last four types of </SectionTitle> <Paragraph position="0"> questions are implemented for a small subset of French (simple sentences).</Paragraph> <Paragraph position="1"> The first communication-mode (how does one say <idea>?) raises an interesting problem : how to tell the computer what one wants to say (message). The fundamental question here is in what terms to code thought and access it. Obviously, there are several ways. One could ask in another natural language (translation), one could use images, or one could use some form of metalanguage.</Paragraph> <Paragraph position="2"> In this paper we discuss some of the problems that arise by using a metalauguage. We then show how a special category of thought, tense, can be communicated by nsing a hybrid form of representation. But, before doing so let us give a short description of the system. For more details see \[ 29, 30, 31 \].</Paragraph> </Section> <Section position="4" start_page="0" end_page="0" type="metho"> <SectionTitle> 2 Description of the system </SectionTitle> <Paragraph position="0"> The dialogue is initiated by specifying the communication mode. Let us suppose that the user had started with the first question: How does one say <idea> ? In that case the system presents a menu (type hierarchy) from which the user has to choose: Speech act : statement, question, command Actions - processes: taxonomy of verbs tense : present, past, future, etc.</Paragraph> <Paragraph position="1"> Discourse objects : taxonomy of nouns number : singular, plural communic, status : definite, indefinite, Attributes: taxonomy of attributes By choosing specific values from a set of alternatives, the user tells the system what he wants to say. 4 As the dialogue develops, the system builds the underlying meaning in the form of a semantic network. It then invites the user to try to express this meaning, after which it outputs its own form.</Paragraph> <Paragraph position="2"> As one cat* see from Figure 1, the screen is divided into five parts. The large window at the top represents the underlying meaning of the message a student is trying to convey.</Paragraph> <Paragraph position="3"> The next two windows contain respectively the user's attempt to express this meaning and the system's version. Possible mismatches between these two versions are highlighted on the screen. This allows the system to draw the student's attention to errors. Actually, by looking at Figure 1 you can see that the student made a mistake in the verb agreement &quot;regard6&quot;. Finally, the two windows at the bottom represent, from left to right, a snapshot of the system's rcorozy of meaning and the user's mexmry of festa . The former is a device to display, hence to recall the underlying conceptual representation of a specific sentence chosen from the rt~m~ry of fern window, whereas the latter is an incrementally built database (trace) of all the sentences encountered so far. The idea behind this separation is to allow the user to make a contrastive analysis of meaning and form between</Paragraph> </Section> <Section position="5" start_page="0" end_page="0" type="metho"> <SectionTitle> 4 For more details concerning the interface controlling the </SectionTitle> <Paragraph position="0"> conceptual input (What to say-component), see Zoek (1991).</Paragraph> <Paragraph position="1"> ACRES DE COLING-92, NANTES, 23-28 AO~t' 1992 4 7 6 PREC. OV COL1NG-92, NANTES, AUO. 23-28, 1992 two senteuces. 5 Choosiug a seateucc ill thC lt-t6~tlOrr y Of foran window gives a representation of the seutence's tueaniug in the mc~'ory of n~..anin9&quot; wintlow. By comparing the surface forut and the underlying meaning of two sentences, file user can appreciate the relationship between meauing aud rural. The critical feature, dig one that is respousible for the difference of form, is highlighted by the system. In our exantple it is the value &quot;singular&quot;.</Paragraph> <Paragraph position="2"> Past this point, the user has various options : eithel he continues in the basic communication m<rde (How doe~ one nay<idea> ?), or he changes the kind of question he wants to ask. Let us suppose that he wants to build a completely different senlence. In this case he. could either go through the whole routine, which i,~ quite cumbersome, or he could perfomt the conceptual changes direetely on the graph. Obviously, this latter metltod is much faster. 6 Actually, everything you see on the graph, except deepcase relations, is considered by the system as a vaiiable whose value may be changed directely by the user. ht order to do so, he clicks on any of the showu attributes (verb, tense, mode, etc.) and chooses a new value. For example, if he clicks on the verb &quot;regarder'&quot; (to watch) the system answers by displaying a list of cmtdidates from which we must choose.. By clicking on the feature &quot;present&quot;, rite system shows different values ( present, past, future, etc.) of the variable &quot;tense&quot;, etc. Everytiute the system is given some piece of information it will change the meaning representation accordingly and, il asked, output rite corresponding form. For example, if one started from sentence (at asking the system to chm~gc the number of the direct object lY=om &quot;singular&quot; to &quot;plural&quot; it would produce (b). If one asked to change the tense from &quot;simple past&quot; to &quot;present perfect&quot;, it would produce (e), etc.</Paragraph> <Paragraph position="3"> a) Le garcon regarda In lille (the boy watched tile J;jr!) b) Le garcon regarda!ees fill e~s (file boy watched the gir~. ) c) Le garcon a re rrrrrrrr~d.~ los filles (the Ir~,y has watched the girls) AS one can see, this method allows h)r local as well as for global changes. Actually, the dialogue described corresponds to the commuttication mode 5. If one changes only one value each time, asking the system to tell right away how this meaning change is reflected in form, one can very quickly build attd explore a large search space. It should be noted, that this kind of dialogue between man and machine is much faster attd 5 See communication mode 8 : What is the difference between <form x> and <form y> ? 6 Actually, that is one of the major advantages of abstract representations compared to, let us say, icons. Another advantage is that this kind of representatimt shows on-line how conceptual or pragmatic choices affect the intermediate structure, hence more or less directly tile final form. In consequence, by displaying on-line the way how the intermediate structure changes after each choice, we have a means of moving from a black box to a glass box. The former only shows how changes of the input '(conceptual choices) are reflected in the output, whereas the latter also shows how discourse choices (topicalisation, word choice, etc.) affect the intermediate levels.</Paragraph> <Paragraph position="4"> less tedious than it would be betweeu a studeut anti a teacher. The change of trieauiug attd rite system's generation of file corresponding forrn take about a ,second, cvea lor ml unffaiued u~r.</Paragraph> <Paragraph position="5"> Auother contmunicalitm mode the system allows for is callod: wtuat wot~q d t~,~ i~ <syntactic modificatkm>? This ntode allows rite user to perforut certain trausformations such as passive voice or prnnominalizatiou. In the latter case, the system will ask the user to specify which element he wants pronominalized (the boy, the girl, or both). A&sume tlutt, starting from the conceptual structure underlying sentence (at, the user wauts to proaontiualize respectively the agent, the object, and finally both arguntents. In these case,s he would get the following outputx : II regarde la fille. (he watches the gkl) I.e gargon la regartle. (the Ix W watches her) 11 ht regarde. (lie watches her) By exploring and contrasting the diflerent possibilities, the user is nteant to leant how variations of nteani,tg are reflectt~.l in hirer.</Paragraph> </Section> <Section position="6" start_page="0" end_page="0" type="metho"> <SectionTitle> 3 Discussion </SectionTitle> <Paragraph position="0"> We have described a computerized learning euviromnent that has several iuterestittg features : (at it allows a potential user to learn French on his own. (b) it fosters learning through exploratkm (hypothesis-testing, inductive learning); (c) it allows the user to ask questions rather I\]lan simply answer them. As he knows best what his needs are, he is untst likely to ask the right questions at the rigid moment; On the other hand, the system has also various shortcomings: (at the linguistic coverage is extremely small : only very simple structures c~tn be used; (b) the conceptual interface is a surface- rather than a deep-structure compouent (it already contains the lexieal items, i.e., the progrant thinks ill terms of the target language); (c) the size of the discourse universe : one can duly talk about a very limited range of facts; (d) the rigidity of the conceptual coutponeut : the order in which lhe meaning is conveyed is defined a priori. The choice of verbs always precedes the choice of the uouns; (e) the terminology used (metalanguage) may be ilmccessible to the linguistically innocent user.</Paragraph> <Paragraph position="1"> In the remainder of this paper we will only be eoncenteal with the last point. More precisely, we will focus on the problem ol conveying the notious of time, tense attd aspect. For a proposal of how to increase the power and flexibility of the conceptual compoueat see \[33, 34\].</Paragraph> <Paragraph position="2"> 4. Sentence generation and tense specification While much atteutiou has been devoted to rite problem of representing and interpreting tense \[2, 13, 13a, 13b\], little, if any atteution has been devoted to the problem of generating tense ill the context of natural language generalimt. A notable exception is the work of V. Ehrich \[6\] who describes the properties of a situation (a convenient neutral term for making indiscriminately reference to eveals, actious, processes, states) in terms of category, aspoct, relation, and position.</Paragraph> <Paragraph position="3"> Sentence geaeration consists of translating a conceptual swucture into a surface form. Obviously, information concerning time, tense aud aspect is part of the ACrE.S DE COLING-92, NANTES, 23-28 ao(rr 1992 4 7 7 Picot. ol: COI.ING-92, NANTES, AUG. 23-28, 1992 conceptual input. The problem is in what terms a naive user could communicate these abstract notions.</Paragraph> <Section position="1" start_page="0" end_page="0" type="sub_section"> <SectionTitle> 4.1 The problem of choosing the right form </SectionTitle> <Paragraph position="0"> Tense can be communicated by choosing among a set of metulinguistic terms (past, present, future, etc.). These terms are actually used in schools, in text books and even in intelligent tutoring systems \[7, 8\]. Yet this approach has several shortcomings : (A) Students are not linguists. While notions such as &quot;past, present, future&quot; seem to be meaningful when we deal with simple tenses, things change rapidly as soon as we move to more complex tenses like present continuous, past perfect, etc. The student is certainly short of intuition when he comes across tenses for which there is no equivalent in his mother tongue.</Paragraph> <Paragraph position="1"> (B) There is no one-to-one correspondance between grammatical tenses and semantic values. The &quot;present forms&quot; are quite often used in order to convey the meaning of the past, the present, or the future (1-4). In a similar vein, past forms can be used with a present value (3) 1) J'arrive fi l'instant. (I have just arrived.) pl~, 2) Je r~fl~chis. (I'm thinking.) pI'g~,, 3) J'arrive duns un instant. (I'm coming right now.) 4) J'arrive. (l just arrived.) PKST, - (I ant coming.)eXYlx~: 5) Je venais vous demander une augmemntion (I just wanted to ask for a salary increase) Pr~.qEh~;, (C) The possibility of using a certain form depends on the context of the sentence (presence of a temporal adverbial, nature of the subject and complements). 7 Consider the following examples : 6) Je suis content (I am very glad.); 7) * J'dtais content (I was glad.); 8) * J'ai ~t~ content.(I have been glad.); 9) Hier, j'~tais content. (Yesterday, I was very glad.); l O) * Hier, j'ai $t$ content. (Yesterday, I have been glad.); ll) Hier, j'ai ~t~ content d'apprendre ton retour (Yester null day, I wa.v glad to learn that you were coming back). While (6) is quite acceptable, its translations into past -be it the simple past (7), or past perfect (8),-- need an explicit reference. Moreover, the form of the past perfect in French can only be used if one refers to an event, -the ingression of a state,-- as in (11).</Paragraph> <Paragraph position="2"> 5. How to visualize tense ? Icons provide a very natural way of representing tense. Several grammars for English \[21\] and for French \[10\] make use of them. We draw on these sources and adapt them for SWIM. In order to do so we provide the user with a basic set of elements for translating tense into icons : (a) a time axis; (b) a representation of the point of speech (NOW) on the time axis; (c) a set of types of 7 When using a specific tense one should also be sensitive to the kind of inferences the addressee might draw. For instance, the following two sentences have completely different implications. : (a) I've been thinking about you. (b) I thought about you. While (a) suggests that one cares for the person one is talking to, (b) implies that one doesn't care any more. (We owe this example to Nicolay Vazov from the university of Sofia) situations (state, event, etc.); (d) a frame of reference (a window); and/or (e) a point of reference.</Paragraph> <Paragraph position="3"> The time axis represents the intuitive notion of time as an oriented linear structure. The time of vertical arc locates the time of utterance: on the left hand side is the past, on the right the future. The situation to be referred to can be communicated by choosing an icon from a set of alternatives (see figure 7). The last two components, the frame and the point of reference represent the way (point of view) the speaker looks at the situation.</Paragraph> <Paragraph position="4"> We start by describing these basic elements and illustrate their use through examples. We then explain how these elements are related to form a coherent metulinguistic vocabulary.</Paragraph> </Section> <Section position="2" start_page="0" end_page="0" type="sub_section"> <SectionTitle> 5.1 The basic elements </SectionTitle> <Paragraph position="0"> The minimal machinery necessary for generating tense is composed of a time axis with a point of speech (now) and a means of locating an action/event with respect to this point of speech (Figure 5).</Paragraph> <Paragraph position="1"> point of speech o o time axis O Figure 5 Reichenbach used the following concepts to characterize tense: a point of speech (S), a point of reference (R) and a point of event (E). 8 Furthermore he used two kinds of connectors in order to express the fact that two events coincide with one another C,&quot;), or that an event preceded another C_&quot;). The following formulas shall illustrate his present tense I see Paul simple past I saw Paul present perfect I have seen Paul past perfect I had seen Paul simple future I will see Paul future perfect I will have seen Paul Since then the system has been extended or re-interpreted by a number of authors \[3a, 12a, 12b, 24, 24a, 25a,28a\]. (A) Types of situation and corresponding icons: A sentence refers to some point in time (temporal situation). A situation will be represented by any of the following icons 8 Voint of speech refers to the very moment in which the utterance takes place (now). The point of reference is the perspective from which the event is considered. The r~int of event is the very moment at which the event took place (yesterday).</Paragraph> <Paragraph position="2"> A state is considered as covering a stretch of time with no definite boundaries. The icon reperesenting this suggests this open-endedness by having fuzzy delimiting zones. Both ongoing processes and activities have a well-defined starting point but no determined point of termination. Note however, that activities can be interrupted at any time and be reported as events. Let us suppose that &quot;Paul was swimming&quot;, and then stopped. This can be reported by ~Paul swam,. Telie processes do not have this property, because they have some natural point of completion. If <<Paul was swimming across the Channel~, and then stopped swimming, we could describe this situation as Paul has been swimming, but we could not say ~Paul swam across the Channel.~> In that case, the point of completion can be referred to, even if it is never reached: ~Paul was swimming across the channel, but he never made it>>. The situation can also be considered as indeteffninate: ,Paul was swimming across the Channel when I last heard about him>~.</Paragraph> <Paragraph position="3"> An event has both a starting point and a point of termination. It can be punctual or not. According to Reichenbach it is represented as a point or au interval, whereas we allow for the additional use of a frame. An event can also be considered with regards to the result of its occurrence. There are events with a resulting state. In the corresponding icon, we represent this state as adjacent to the event which has brought it about. Usually, the precise nature of this resulting state needs to be inferred (cf. \[10\]): It has been raining; in consequence the pavement is wet, it got comer, there are puddles in the street, my hairdress is spoiled, etc.</Paragraph> <Paragraph position="4"> Itabitual events are an undetermined ||umber of events. The icon of habitual events is meant to suggest their resemblance to states. It should &quot;also be noted that the number of events may be conceptnally indefinite.</Paragraph> <Paragraph position="5"> Compare: (a)l played tennis many times last year.(b) 1 used to play tennis when I was a young man In gust case we are dealing with a sequence of individual events, not with a habitual event. Hence it is quite possible to continue the dialogue by asking the following question &quot;how many times did you play?&quot;, while this question .seems quite odd in the second case. (B) Frame of reference, point of reference: Optional elements are a frame of reference and a point of reference, both of which can be manipulated by the user. The former consists of a window which represents the period of time considered by the speaker. It is usually associated with a temporal adverbial (Yesterday Paul visited the Eiffel Tower). The point of reference can be used in order to represent some instant which plays the role of a translated point of speech (ht 1980 Paul had already visited Paris twice.).</Paragraph> </Section> <Section position="3" start_page="0" end_page="0" type="sub_section"> <SectionTitle> 5.2 Using these elements tn produce a time scenario </SectionTitle> <Paragraph position="0"> The procedure is as follows: (a) Choose a suitable type of situation (icon) to represent the temporal structure of the situation; (b) Position the icon relative to the point of speech; (c) If necessary, introduce and position a frame and/or point of relerence and position it.(d)In the overall representation, some part of the situation should be adjacent to, or included in an element of reference (point of speech, point of reference, frame of reference).</Paragraph> <Paragraph position="1"> If not, reexamine step (c).</Paragraph> <Paragraph position="2"> Suppose we have an untensed representation of : ~Paul aime la cuisine italienne, (Paul likes Italian cooking). In order to generate the tense, we choose a state and the position of the point of speech on the time axis (Figure 8a). From this representation the corresponding time (present tense) can be generated.</Paragraph> <Paragraph position="3"> Since no direct reference to the point of speech is available, a frame of reference is necessary. Here it plays the same role as the point of speech in figure 8a. If the user adds the adverbial ~<l'an pass6,~ (last year) as a marker of reference, we get ~<l'an pass6, Paul aimait la cuisine ACTES DE COLlNG-92, NANTES. 23-28 ho~r 1992 4 7 9 PROC. OF COLING-92, NANTES, AUG. 23-28, 1992 italienne~, (Last year Paul liked italian cooking.) The interpretation of maimer la cuisine italienne,(to like italian cooking) in terms of a state should be distinguished from its interpretation as an event. The latter would be the instantaneous change from one state to another. That's why we need further specifications: ~Quand Paul a rencontrd Gina, il a aimg la cuisine italienne.~ (When Paul met Gina, he began to like Italian cooking). Figures 8c and 8d show two possible representations of similar, yet different situations.The completion of the work is not precisely determined in this case.</Paragraph> <Paragraph position="4"> Among the difficulties faced by a learner of French is the dual value of &quot;pass6 compos6&quot;. Consider, (tlier), j'ai dcrit mon article - \[ (yesterday) 1 wrote my paper\] In one interpretation (figure 9a), the writing of the paper is considered as a past event. Locating the action within a reference frame requires the use of an adverbial like ~hier>> (yesterday).</Paragraph> <Paragraph position="5"> 9t)11iC/~ jqu &:tit non trtiele (I wrote my paper yesterday) ....................................................................................................................................................... i ii I::::::~ This case is to be differentiated from the situation depicted in Figure 9b. Here the implicit reference is now.</Paragraph> <Paragraph position="6"> The past event is considered with respect to the state resulting from it (present relevance). In fact, the same tense is used in this ease in French, whereas <<Yesterdayl wrote my paper~ would be used in English in case (9a), and e.l have written my paper~ in case (9b).</Paragraph> <Paragraph position="7"> Another typical case of ambiguity is the use of the &quot;present tense&quot; in French. The Figures 9c and 9d, while different in English, yield the same form in French. The first one (9e) signals habitual or repetitive use of the present tense, corresponding to <~I play tennis~. The second situation corresponds to &quot;1 am playing tennis&quot;, implying an ongoing activity at the time of speech.</Paragraph> <Paragraph position="8"> Please note that the first situation does not imply any actual activity at the time of speech, but only a general validity of a kind of property. As the icon suggests, it looks very much like a state.</Paragraph> <Paragraph position="9"> Our classification of types of situation (cf. also \[2\]) is based on conceiving the temporal structure of a situation as a result of (a) the lexical meaning, the tense and the aspect of a given verb, (b) the nature of the subject, the complements and the time adverb'rals.</Paragraph> <Paragraph position="10"> Lexical meaning : We basically subscribe to Vendler's typology \[26\] who classifies situations in terms of states, activities, accomplishments and achievements.</Paragraph> <Paragraph position="11"> Nakhimovsky, in a more recent classification \[17\], introduces additional features (generic vs. specific resources for atclic processes) to Vendler's punctuality, stativity, and telieity. Our classification is based on four classes of lexical meanings, corresponding to combinations of the features: punctuality, stativity, telicity.</Paragraph> <Paragraph position="12"> * punctual events (punctual, non stative, atelic); * states (non punctual, stative, atelic); * telic processes.</Paragraph> <Paragraph position="13"> * atelic activities; Aspect is related to the perspective from which a given situation is viewed. Following Comrie \[4\], we distinguish between perfect, perfective and imperfeetive aspect. In French, the imparfait (continuous paso is a typical imperfective form: a situation is considered from the inside. Perfective, on the other hand, considers a situation as a whole. Perfect is related to the consideration of a given event together with a new state which is a consequence of this event happening, for example, I have prepared some coffee.</Paragraph> <Paragraph position="14"> In our system, perfect is represented by an event with a resulting state. Aspect plays a dual role: it determines the type of situation and it allows for choosing a specific frame of reference.</Paragraph> <Paragraph position="15"> Lexical meaning combined with the aspect of the verb, the types of the subjects and complements, and the temporal adverbials yield the type of situation. For example, the verb dcrire (to write) has an intrinsic lexical meaning : atelic activity. However, it can change : Paul dcrivit un roman (John wrote a novel) : telic process; Paul dcrit des romans (John writes novels) : atelic activity; Paul dcrivait an roman (John was writing a book) : ongoing process.</Paragraph> <Paragraph position="16"> 6.2. How to choose the right tense .9 The following table shows how tense could be computed on the basis of an iconic representation of a situation. The system determines the position of the main part of the situation relative to the point of speech (PS). The qualification is necessary only in the case of an event with a resulting state, where the event is the main part of the situation.</Paragraph> <Paragraph position="17"> If the main part of the situation is posterior to the point of speech, a future tense is chosen by default, though present tense remains a possible candidate. Using either or amounts to communicating a special modal nuance.</Paragraph> <Paragraph position="18"> ACT,S DE COLING-92, NArcr~s, 23-28 AOUT 1992 4 8 0 PROC OF COLING-92 NANTES, AUG. 23-28, 1992 ~mr tum~ fdlo. PS {~nt)} la classe, les dtudiants travaill.</Paragraph> <Paragraph position="19"> aient (When the headmaster entered the classroora, the students were working ); (2) Quand le directeur est entr~ dam la classe, les ~tudiants ont travaiIM (When the headmaster entered the classroom, the students began to work ).</Paragraph> <Paragraph position="20"> See figure 10 The first case represents an ongoing process or activity, with an event occuring somewhere in the middle of it, while the second is a sequence of two adjacent events. So far we handle the case If the main situation is prior to the time of speech, the conclusion depends on the presence of a point of reference (PR) prior to the time of speech. If no such point is ~\],:i &quot; ......... &quot;&quot; - \[::iiiil::i '&quot; .......... &quot; &quot; l!!iil t.,, ..... u, ,.d,. ........ , r ~1 ~.~.'~'=d ~,,-~a~o,. li~i ~%!::i~i::::~i~::~i~::~!~:: lh~.,~ ...... d ~. ~. \[::~:.~ Figure 10 specified, and if the type of situation is an event, one can use the past perfect. In the case of an event or a punctual event, the past perfect is a stylistic alternative (polished style).</Paragraph> <Paragraph position="21"> Temporal adverbials are classified as (a) time-position adverbs (last night, on Monday); (b) as span and duration adverbs (for a month, up to 1979); or (c) as frequency adverbs (usually, often). Temporal adverbs constrain tense generation. Durational adverbs may enforce a habitual meaning on verbs having an intrinsic punctual meaning : <<He has been diving for several months now.~, Temporal subordinate clauses: In the case of simple sentences, the task of determining the tense from an icon is straightforward. More subtle strategies are needed in sentences with temporal subordinate clauses 9. Suppose the main clause concerns <<students working>~ (PAST), whereas the subordinate clause is <<the headmaster entering the classroom ~ (PAST). Let the temporal conjunction be quand (when). Then we have two possibilities: 9 We leave aside the problem of generating subordinate clauses in the subjunctive mood; many temporal conjunctions (e.g. avant que : before) require the use of the subjunctive mood.</Paragraph> <Paragraph position="22"> of quand (when), using icons and strategies similar to the ones described by Moons & Steedman \[16\].</Paragraph> <Paragraph position="23"> The way in which temporal subordinate clauses reflect on the types and order of the situations has been examined in the literature (\[24, 15, 16\]).</Paragraph> </Section> </Section> class="xml-element"></Paper>