******************************************************************** ELECTRONIC NEWSLETTER ON REASONING ABOUT ACTIONS AND CHANGE Issue 98029 Editor: Erik Sandewall 17.3.1998 Back issues available at http://www.ida.liu.se/ext/etai/actions/njl/ ******************************************************************** ********* TODAY ********* A few days ago, Pat Hayes argued in this Newsletter that a representation of time can best be developed using only intervals as the primitive notion. Today, Jixin Ma and Brian Knight return with arguments to the opposite. This Newsletter also contains the CFP for the upcoming TARK-98 conference, where the period of submission has been extended. As usual, the web version of the Newsletter contains the came information with "hot" (= clickable) links. ********* DEBATES ********* --- ONTOLOGIES FOR ACTIONS AND CHANGE --- -------------------------------------------------------- | FROM: Jixin Ma -------------------------------------------------------- After reading Pat's answers to our claims/arguments about the ontology for time, we would like to raise the following questions/arguments: 1. First of all, it is not clear what's the exact role that time points play in Pat's formulation, although, according to Eric's understanding, Pat Hayes "argues in favour of an ontology for time where intervals are the only elementary concept and timepoints play a secondary role". As Pat points out in his answers (in agreement with our opinion as state in our claims), "if we take points and intervals as basic, there is no need to do this", i.e., deal with the question of whether intervals are open or closed. However, it is not clear what's the exact meaning of "taking points and intervals as basic". Are they both taken as primitive temporal objects, or, as Allen suggests, points are thought as places where intervals meet each other? 2. Pat argues that "the question is whether it makes sense to say that something is true at points". However, his argument is quite confused: in the first place, he claims "truths hold not at points but during intervals" (as for the case when one insists that interval endpoints are "in" the interval). Later, he states "Some truths may be instantaneous, ie true only at points; others make sense only when asserted to hold during noninstantaneous intervals". So, what's the answer to the question "whether it makes sense to say that something is true at points"? 3. Pat's claims that one may identify interval with point t, or distinguish form t, or even forbid instantaneous intervals completely. However, what's the choice? Do we need points (instantaneous intervals) or not? Let's consider the case that we do (in fact, for general treatments, we DO need them). For this case, Pat's states that if meets(, ) & meets(, ) then meets(, ) (In fact, it seems in Pat's formulation, we always have meets(, ) and meets(, ) etc., since the intervals are uniquely defined by their endpoints). Below are some problems with this formulation: I. As noted by Pat himself, "an instantaneous interval meets itself", though the "basic" points are totally ordered. How to characterise the relation between them? Pat's gives a suggestion: to characterise them without mentioning points explicitly. Then, what's the relationship between points and intervals? II. How to define other relationships between intervals like those introduced by Allen? For instance, it is intuitive to say that meets(, ) & meets(, ) imply before(, ). However, in this case,, one would have both meets(, ) and before(, ), and hence "meets" and "before" would not be exclusive to each other. III. By saying meets(, ), meets(, ), and meets(, ), one can only express the first case, that is case a), but not the other two cases, that is case b) and case c), as we demonstrated in our former arguments. 4. Pat argues that "I'm largely in agreement with Jixin about points and intervals, although I dont think its got anything to do with knowledge". But it does. In fact, as pointed out by Pat himself, "if you want to know whether the light was on or not, you have to say which interval you are talking about". In other words, if the (additional) knowledge of "which interval you are talking about" is given (e.g., in terms of which interval is open/closed at the switching point, or in terms of the corresponding meets relations - "knowledge"?), we can say whether the light was on or not. 5. Pat also argues that his formulation is simpler (and elegant). In what aspects, compared with which formulation? It seems that it still needs a lot of axioms to characterise the formal structure, especially when issues such as density, linearity, boundness, etc, are to be addressed. Jixin & Brian ********* CALENDAR ********* --- FORTHCOMING CONFERENCES AND WORKSHOPS --- TARK-98: Theoretical Aspects of Rationality and Knowledge. Evanston, Ill., USA, 22-24.7, 1998. Papers due: 31.3 1998. General information: http://www.tark.org/ Broadcast message: http://www.ida.liu.se/ext/brs/confi/cfp/TARK-98.txt ---------------------------------------------------------------------------- Please note that the deadline for submissions has been extended to March 31: ---------------------------------------------------------------------------- Seventh conference on THEORETICAL ASPECTS OF RATIONALITY AND KNOWLEDGE TARK VII (previously: Theoretical Aspects of Reasoning about Knowledge) July 22-24, 1998 Evanston, Illinois, USA About the conference ==================== The mission of the bi-annual TARK conferences is to bring together researchers from a wide variety of fields -- including Artificial Intelligence, Cryptography, Distributed Computing, Economics and Game Theory, Linguistics, Philosophy, and Psychology -- in order to further our understanding of interdisciplinary issues involving formal reasoning about rationality and knowledge. Topics of interest include, but are not limited to, semantic models for knowledge, for belief, and for uncertainty, bounded rationality and resource-bounded reasoning, commonsense epistemic reasoning, epistemic logic, knowledge and action, applications of reasoning about knowledge and other mental states, and belief revision. TARK VII will be coordinated with the 1998 Microeconomic Theory Workshop at Northwestern University, sharing talks for about a day and a half, on topics that are of interest to both audiences. Previously a by-invitation-only conference, TARK is now open to all interested attendees. Information for Authors ======================= Submissions are now invited to TARK-VII. Please submit 15 copies of a detailed abstract (not a full paper) to the address below. Strong preference will be given to papers whose topic is of interest to an interdisciplinary audience, and papers should be written so that they are accessible to such an audience. Papers that are submitted to the TARK-Microeconomic Theory joint sessions should be identified as such, and will be separately evaluated by the two program committees. Based on interest considerations, a paper may be accepted for presentation in one event but not in the other. Conversely, the committees may include a regular TARK submission in the joint sessions. Papers will be held to the usual high standards of research publications. In particular, they should 1) contain enough information to enable the program committee to identify the main contribution of the work; 2) explain the significance of the work -- its novelty and its practical or theoretical implications; and 3) include comparisons with and references to relevant literature. Abstracts should be no longer than ten double-spaced pages (4,000 words). If possible, an email address for the contact author should be included. Papers arriving late or departing significantly from these guidelines risk immediate rejection. Economists should be aware that special arrangements are being made with certain economics journals (in particular, with International Journal of Game Theory, Games and Economic Behavior, and Journal of Economic Theory) so that publication of an extended abstract in TARK will not prejudice publication of a full journal version. The deadline for submission of abstracts is March 31, 1998. Authors will be notified of acceptance by May 8, 1998. Camera-ready copies of the accepted papers will be due by June 10, 1998. One author of each accepted paper will be expected to present the paper at the conference. The conference proceedings will be published. Program Committee *********************** Michael Bacharach (University of Oxford, Philosophy, Economics, and Statistics) Cristina Bicchieri (Carnegie-Mellon University, Philosophy) Craig Boutilier (University of British Columbia, Computer Science) Eddie Dekel (Northwestern University, Economics) Adam Grove (NEC Research Institute, Computer Science) Aviad Heifetz (Tel-Aviv Univeristy, Economics) John Horty (University of Maryland, Philosophy and Computer Science) Daniel Lehmann (Hebrew University, Computer Science) Ron van der Meyden (University of Technology, Sydney, Computer Science) John-Jules Meyer (Utrecht University, Computer Science) Drazen Prelec (MIT, Psychology and Management) Aldo Rustichini (Tilburg University, Economics) Robert Stalnaker (MIT, Philosophy) Program Chair ************* Itzhak Gilboa (Boston University and Tel-Aviv University, Economics) email: gilboa@econ.bu.edu Address for Submissions *********************** TARK c/o Games and Economic Behavior Kellogg Graduate School of Management Northwestern University Evanston, IL 60208 USA Local Arrangements ****************** Eddie Dekel Department of Economics Northwestern University Evanston, IL 60208 USA email: dekel@merle.acns.nwu.edu (708) 491-4414 (phone) (708) 491-2530 (fax) Latest details on the conference can be found at http://www.tark.org. ******************************************************************** This Newsletter is issued whenever there is new news, and is sent by automatic E-mail and without charge to a list of subscribers. To obtain or change a subscription, please send mail to the editor, erisa@ida.liu.se. Contributions are welcomed to the same address. Instructions for contributors and other additional information is found at: http://www.ida.liu.se/ext/etai/actions/njl/ ********************************************************************