AIList-REQUEST@SRI-AI.ARPA (AIList Moderator Kenneth Laws) (01/15/86)
AIList Digest Wednesday, 15 Jan 1986 Volume 4 : Issue 7 Today's Topics: Seminars - Reasoning About Hard Objects (BBN) & LOGIN: A Logic Programming Language with Inheritance (MIT) & Temporal Reasoning and Default Logics (SU) & LISP/Prolog Memory Performance (Ames) ---------------------------------------------------------------------- Date: 9 Dec 1985 12:10-EST From: Brad Goodman <BGOODMAN at BBNG> Subject: Seminar - Reasoning About Hard Objects (BBN) [Forwarded from the MIT bboard by SASW@MIT-MC.] BBN Laboratories Science Development Program AI Seminars Speaker: Ernest Davis NYU Title: Issues in Reasoning about Hard Objects Date: Monday, December 16th, 10:30a.m. Place: BBN Labs, 10 Moulton Street, 3rd floor large conference room Abstract The physics of rigid solid objects raises two serious problems which have not been addressed in previous spatial and physical reasoning programs. Firstly, the physical properties of solid objects are sensitive to very slight variations in shapes. Therefore, when an ideal shape is used to approximate a real shape, the accuracy of the approximation must be tightly bounded. Secondly, the method of reasoning used by both Forbus and DeKleer of going from one critical point to the next is not, in general, appropriate. Frequently, as in reasoning about a ball going down a funnel, one is interested only in the final outcome (the ball goes out the funnel) and not in any of the intermediate critical points (collisions between the ball and the funnel). However, it is difficult to state axioms that assert global relationships of this sort in a way that allows them to be used in cases where additional objects enter the picture. ------------------------------ Date: Thu 9 Jan 86 13:37:32-EST From: Susan Hardy <SH@XX.LCS.MIT.EDU> Subject: Seminar - LOGIN: A Logic Programming Language with Inheritance (MIT) [Forwarded from the MIT bboard by SASW@MC.LCS.MIT.EDU.] DATE: Thursday, January 16, 1986 TIME: 3:00 p.m. - Refreshments 3:15 p.m. - Lecture PLACE: NE43-512A LOGIN: A LOGIC PROGRAMMING LANGUAGE WITH BUILT-IN INHERITANCE Hassan Ait-Kaci A.I. Program MCC, Austin, Texas Since the early days of research in Automated Deduction, inheritance has been proposed as a means to capture a special kind of information; viz., taxonomic information. For example, when it is asserted that "whales are mammals", we understand that whatever properties mammals possess should also hold for whales. Naturally, this meaning of inheritance can be well captured in logic by the semantics of logical implication. However, this is not operationally satisfactory. Indeed, in a first-order logic deduction system realizing inheritance as implication, inheritance from "mammal" to "whale" is achieved by an inference step. But this special kind of information somehow does not seem to be meant as a deduction step---thus lengthening proofs. Rather, its purpose seems to be to accelerate, or focus, a deduction process---thus shortening proofs. In this talk, I shall argue that the syntax and operational interpretation of first-order terms can be extended to accommodate for taxonomic ordering relations between constructor symbols. As a result, I shall propose a simple and efficient paradigm of unification which allows the separation of (multiple) inheritance from the logical inference machinery of Prolog. This yields more efficient computations and enhanced language expressiveness. The language thus obtained, called LOGIN, subsumes Prolog, in the sense that conventional Prolog programs are equally well executed by LOGIN. I shall start with motivational examples, introducing the flavor of what I believe to be a more expressive and efficient way of using taxonomic information, as opposed to straight Prolog. Then, I shall give a quick formal summary of how first-order terms may be extended to embody taxonomic information as record-like type structures, together with an efficient type unification algorithm. This will lead to a technical proposal for integrating this notion of terms into the SLD-resolution mechanism of Prolog. With examples, I shall illustrate a LOGIN interpreter. Host: Rishiyur Nikhil (617)253-0237 Nikhil@mit-xx.arpa ------------------------------ Date: 13 Jan 86 1659 PST From: Vladimir Lifschitz <VAL@SU-AI.ARPA> Subject: Seminar - Temporal Reasoning and Default Logics (SU) Next nonmotonic reasoning meeting: A Review and Critique of: "Temporal Reasoning and Default Logics" by Steve Hanks and Drew McDermott Yale/CSD/RR #430 October 1985 by Benjamin Grosof, inquisitioner Thursday, January 16, 4pm MJH 252 Hanks and McDermott in their recent Yale Tech Report pose an example problem in temporal reasoning and claim that none of the leading formalisms for default reasoning (namely Reiter's Default Logic, McDermott and Doyle's modal Non-Monotonic Logic, and Circumscription) adequately capture the type of non-monotonic reasoning that is (what they claim is) desirable in the example. They give an algorithm which does. They go on to conclude rather pessimistically that there seems to be some inherent problem in the semantics of all three default formalisms. In this talk, I review their paper, including their temporal logic. I argue that their example in particular is interesting and suggestive, but that the semantical difficulty that they emphasize arises from an underspecification of the problem. I will go on to suggest how indeed to represent the additional CRITERION satisfied by their algorithm (but not by their formulations in default formalisms). I show how Vladimir's new circumscription presented in our fall sessions of the non-monotonic reasoning seminar can solve the representational problem they pose. I argue that circumscription, because it can incorporate certain kinds of preferences among competing extensions via prioritization, has an advantage over the other two default formalisms, and promises to be able to represent the CRITERION more generally than their algorithm does. I also discuss how their temporal formalism occupies an intermediate place between STRIPS and situation calculus. ------------------------------ Date: Tue, 14 Jan 86 21:47:09 pst From: eugene@AMES-NAS.ARPA (Eugene Miya) Subject: Seminar - LISP/Prolog Memory Performance (Ames) National Aeronautics and Space Administration Ames Research Center SEMINAR ANNOUNCEMENT Joint Ames AI Forum/RCR Branch SPEAKER: Evan Tick Computer Systems Laboratory Stanford University TOPIC: Memory Performance of Lisp and Prolog Programs ABSTRACT: This talk presents a comparison between Lisp and Prolog architectures based on memory performance. A subset of the Gabriel benchmarks was translated into Prolog, compiled into the Warren Abstract Machine instruction set and emulated. The programs were also measured with an instrumented Common Lisp targeted to a Series 9000/HP237. Memory usage statistics indicate how the two langauges do fundamental computations different ways with varying efficiency. DATE: 28 January 1986 TIME: 1030 AM BLDG: 172 ROOM: 233 Tuesday POINT OF CONTACT: E. Miya PHONE NUMBER: (415)-694-6453 emiya@ames-vmsb I am current attending a conference, please send mail or contact my office mate. VISITORS ARE WELCOME: Register and obtain vehicle pass at Ames Visitor Reception Building (N-253) or the Security Station near Gate 18. See map below. Do not use the Navy Main Gate. Non-citizens (except Permanent Residents) must have prior approval from the Director's Office one week in advance. Submit requests to the point of contact indicated above. Non-citizens must register at the Visitor Reception Building. Permanent Residents are required to show Alien Registration Card at the time of registration. ------------------------------ End of AIList Digest ********************