AIList-REQUEST@SRI-AI.ARPA (AIList Moderator Kenneth Laws) (10/24/85)
AIList Digest Thursday, 24 Oct 1985 Volume 3 : Issue 154 Today's Topics: Seminars - Representation of Natural Forms (MIT) & LOGIN: Logic Programming with Inheritance (UPenn) & Database Updates in Prolog (UPenn) & Concurrent Logic Programming (CMU) & Person Schemata (UCB) & NETTALK: Connectionist Speech Learning (UPenn) ---------------------------------------------------------------------- Date: Mon 21 Oct 85 09:55:17-EDT From: "Brian C. Williams" <WILLIAMS%MIT-OZ@MIT-MC.ARPA> Subject: Seminar - Representation of Natural Forms (MIT) [Forwarded from the MIT bboard by SASW@MIT-MC.] Thursday 24, October 4:00pm Room: NE43- 8th floor Playroom The Artificial Intelligence Lab Revolving Seminar Series "Perceptual Organization And The Representation Of Natural Form" Alex P. Pentland AI Center, SRI Int'l and CSLI, Stanford To understand both perception and commonsense reasoning we need a representation that captures important physical regularities and that correctly describes the people's perceptual organization of the stimulus. Unfortunately, the current representations were originally developed for other purposes (e.g., physics, engineering) and are therefore often unsuitable. We have developed a new representation and used it to make accurate descriptions of an extensive variety of natural forms including people, mountains, clouds and trees. The descriptions are amazingly compact. The approach of this representation is to describe scene structure in a manner similar to people's notion of ``a part,'' using descriptions that reflect a possible formative history of the object, e.g., how the object might have been constructed from lumps of clay. For this representation to be useful it must be possible to recover such descriptions from image data; we show that the primitive elements of such descriptions may be recovered in an overconstrained and therefore reliable manner. An interactive ``real-time'' 3-D graphics modeling system based on this representation will be shown, together with short animated sequences demonstrating the descriptive power of the representation. ------------------------------ Date: Tue, 22 Oct 85 18:21 EDT From: Tim Finin <Tim%upenn.csnet@CSNET-RELAY.ARPA> Subject: Seminar - LOGIN: Logic Programming with Inheritance (UPenn) Colloquium 3pm 10-26-85 23 Moore, University of Pennsylvania 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. ------------------------------ Date: Tue, 22 Oct 85 11:35 EDT From: Tim Finin <Tim%upenn.csnet@CSNET-RELAY.ARPA> Subject: Seminar - Database Updates in Prolog (UPenn) Colloquium - 3pm 10-24-85 216 Moore, University of Pennsylvania A LOGICAL APPROACH TO DATABASE UPDATES IN PROLOG DAVID S. WARREN , SUNY AT STONY BROOK The power of the logic programming paradigm (exemplified by the Prolog programming language) lies in its close relationship to logic. This gives logic programs a clean, simple, and elegant declarative semantics, making them easy to understand and reason about. It has turned out, however, that in order to make Prolog a practical and usable programming language, several computational (and non-logical) extensions must be added. These extensions include the ``not'' operator, the ``setof'' operator, the ``var'' predicate, and the ``assert'' and ``retract'' operators. To the extent that these operators are non-logical, they destroy the declarative semantics of programs that use them. Such a program can only be understood by knowing its computation sequence. Progress has been made in providing a logical semantics for the ``not'' operator in Prolog, and the circumstances under which Prolog's negation as failure rule coincides with logical ``not'' are now reasonably well understood. This has allowed Prolog programs which use the ``not'' operator (meeting the appropriate constraints) to be understood declaratively. This talk describes an approach to providing a logical semantics for the Prolog operator ``assert''. We use a simple modal logic, which leads to a slightly different operational semantics for ``assert'' and suggests ways that the assert operator should be restricted in application. The resulting system has interesting implications for a theory of database updates. ------------------------------ Date: 22 Oct 1985 1109-EDT From: Lydia Defilippo <DEFILIPPO@C.CS.CMU.EDU> Subject: Thesis Oral - Concurrent Logic Programming (CMU) ABSTRACT OF THESIS PROPOSAL Speaker: Vijay A. Saraswat Date: Friday - 1 November, 1985 Time: 10:00 am Place: 7220 Topic: CONCURRENT LOGIC PROGRAMMING LANGUAGES The domain of logic programming languages, consists, of the most part, of programming languages based on Horn logic which provide modified forms of top-down, SLD-refutation execution engines. A program in these languages consists of a set of definite clause axioms with (perhaps implicit) control information for guiding the underlying engine. Execution is initiated by the presentation of a conjunction of goals or queries and terminates when the engine, following the prescribed control, discovers either a proof of the goals, or the impossibility of such a proof. Concurrent logic programming (CLP) languages provide execution engines capable of pursuing concurrently proofs of each of the goals in a conjunctive system (so-called and-parallelism) and also different possible proof paths for each goal (or-parallelism). Examples of existing concurrent Horn languages are Concurrent Prolog, Parlog, GHC, Delta-Prolog and CP[!,|,&]. In this thesis I propose to lay a sound theoretical foundation for, and explore the paradigm of, CLP languages. Specifically, I propose to investigate the design, semantics, implementation and use of such languages. The thesis is intended to make contributions to each of the following areas: -- programming language design, via -- an understanding of the design space for concurrent programming languages based on annotated Horn logic, -- the design of a paradigmatic CLP language (CP[!,|,&,;]) providing a reasonably complete set of control structures for the parallel exploration of the refutation search space, and, -- an extensive comparison of CLP languages with related computational models outside the realm of logic programming, such as Actors, CSP, data-flow languages (including the systolic computational model) and constraint-based languages -- theoretical computer science via an understanding of the formal (operational and denotational) semantics of, and reasoning systems for, concurrent logic languages, including an understanding of the `logic' in such languages, -- programming language implementation, via a compiler-based implementation of the specific concurrent language CP[!,|,&] targetted to a uniprocessor machine, -- the `correct' design of efficient concurrent algorithms in the framework of unification-based concurrent logic programming languages, -- knowledge representation languages, via the design of a `higher-level' object-oriented, schema-based language featuring multiple inheritance with exceptions, and its implementation in Cp[!,|,&]. ------------------------------ Date: Wed, 23 Oct 85 13:52:25 PDT From: admin@cogsci.Berkeley.EDU (Cognitive Science Program) Subject: Seminar - Person Schemata (UCB) BERKELEY COGNITIVE SCIENCE PROGRAM Fall 1985 Cognitive Science Seminar - IDS 237A Tuesday, October 29, 11:00 - 12:30 240 Bechtel Engineering Center Discussion: 12:30 - 1:30 in 200 Building T-4 ``Person Schemata'' Mardi J. Horowitz M.D. Professor of Psychiatry, U.C.S.F. The speaker directs the recently formed Program on Cons- cious and Unconscious Processes of the John and Catherine T. MacArthur Foundation. Research on person schemata is one of the core agendas of this program. After a brief description of the program, the discussion will focus on clinical phenomena as segmented by different states of mind in a single individual. By examining the confi- guration in each state of mind as it occurs over time, it may be possible to infer what the self schemata and role relation- ship models are that organize thoughts, feelings and action into observed patterns. The theory that forms the basis for such inferences includes the postulate that each person's overall self organization may include a partially nested hierarchy of multiple self-concepts. A frequent set of states of mind in pathological grief reactions will provide a concrete illustration of phenomena, methods of inference, and a theory of person schemata. ------------------------------ Date: Wed, 23 Oct 85 16:43 EDT From: Tim Finin <Tim%upenn.csnet@CSNET-RELAY.ARPA> Subject: Seminar - NETTALK: Connectionist Speech Learning (UPenn) Colloquium - University Of Pennsylvania 3pm 10-29-85, 216 Moore NETTALK: TEACHING A MASSIVELY-PARALLEL NETWORK TO TALK Terrence J. Sejnowski Biophysics Department, Johns Hopkins University Text to speech is a difficult problem for rule-based systems because English pronunciation is highly context dependent and there are many exceptions to phonological rules. A more suitable knowledge representation for correspondences between letters and phonemes will be described in which rules and exceptions are treated uniformly and can be determined with a learning algorithm. The architecture is a layered network of several hundred simple processing units with several thousand weights on the connections between the units. The training corpus is continuous informal speech transcribed from tape recordings. Following training on 1000 words from this corpus the network can generalize to novel text. Even though this network was not designed to mimic human learning, the development of the network in some respects resembles the early stages in human language acquisition. It is conjectured that the parallel architecture and learning algorithm will also be effective on other problems which depend on evidential reasoning from previous experience. ------------------------------ End of AIList Digest ********************