LAWS@SRI-AI.ARPA (05/06/85)
From: AIList Moderator Kenneth Laws <AIList-REQUEST@SRI-AI> AIList Digest Monday, 6 May 1985 Volume 3 : Issue 60 Today's Topics: Seminars - Frame Problem (UCB) & The Sequential Nature of Unification (SU) & Late-Bound Polymorphic Languages (IBM-SJ) & Inclusive Predicate Existence (CMU) & The LCF Programmable Theorem Provers (UTexas) & Automated Programming (CMU) & Mathematical Discovery and Hindsight (RU) & Foundations of Horn Logic Programming (CMU) & Property Theory and Second-Order Logic (CSLI) ---------------------------------------------------------------------- Date: Wed, 3 Apr 85 15:29:21 pst From: chertok%ucbcogsci@Berkeley (Paula Chertok) Subject: Seminar - Frame Problem (UCB) BERKELEY COGNITIVE SCIENCE PROGRAM Cognitive Science Seminar -- IDS 237B TIME: Tuesday, April 9, 11 - 12:30 PLACE: 240 Bechtel Engineering Center SPEAKER: Jerry Fodor, Philosophy Department, MIT and UC Berkeley TITLE: ``Modules, Frames, Fridgeons, Sleeping Dogs and The Music of The Spheres'' This paper continues the discussion of the frame problem from The Modularity of Mind. It's argued that outbreaks of the frame problem are characteristic of the study of unencapsulated - hence nonmodular - cognitive faculties, and that this explains why the effects of the problem are felt much more strongly when we consider cognition and problem solving than when the topic is perceptual integration. Since unencapsulation is a leading characteristic of any process of rational nondemonstrative infer- ence, it is argued that the solution of the frame problem is not dissociable from the general problem of understanding such processes. This rather gloomy assessment is then compared with views current in AI according to which resort to `sleeping dog' strategies has already made it possible to circumvent the frame problem. I argue that the proposed solution begs the problem. ------------------------------ Date: 3 Apr 85 0000 PST From: Arthur Keller <ARK@SU-AI.ARPA> Subject: Seminar - The Sequential Nature of Unification (SU) CS Colloquium, April 9, 4:15pm, Terman Auditorium ON THE SEQUENTIAL NATURE OF UNIFICATION Cynthia Dwork Massachusetts Institute of Technology Unification of terms is a crucial step in resolution theorem proving, with applications to a variety of symbolic computation problems. It will be shown that the general problem is log-space complete for P, even if inifinite substitutions are allowed. Thus a fast parallel algorithm for unification is unlikely. More positively, term matching, an important subcase of unification, will be shown to have a parallel algorithm requiring a number of processors polynomial in n, the size of the input, and running in time poly-logarithmic in n. This talk assumes no familiarity with unification or its applications. ------------------------------ Date: Wed, 3 Apr 85 17:03:57 PST From: IBM San Jose Research Laboratory Calendar <calendar%ibm-sj.csnet@csnet-relay.arpa> Reply-to: IBM-SJ Calendar <CALENDAR%ibm-sj.csnet@csnet-relay.arpa> Subject: Seminar - Late-Bound Polymorphic Languages (IBM-SJ) IBM San Jose Research Lab 5600 Cottle Road San Jose, CA 95193 Mon., Apr. 8 Computer Science Seminar 10:30 A.M. STATIC TYPE ANALYSIS IN LATE-BOUND POLYMORPHIC LANGUAGES Aud. A Late-bound languages are those which in some way permit the user to delay the binding of meanings to operation names until such time as the operation is actually to be invoked. SIMULA is generally considered to be the first such language and several others, most notably Smalltalk, Zetalisp, and LOOPS, have been introduced in recent years. These languages gain great flexibility from the programmer's ability to write procedures which work on a wide variety of kinds of data, each of which implements a small set of common operations in a data-specific way. This kind of polymorphism, coupled with an inheritance mechanism for sharing code, has enabled the creation of powerful software in remarkably little time and space. The price for this flexibility, however, has until now been the inability to formally reason about programs in these languages. In particular, the lack of a decidable and sound system of static typechecking has prevented the application of even the simplest kinds of compiler optimizations. In this way, late-binding has acquired a reputation for inherent slowness and impracticality. My talk will examine the issue of static typechecking for these languages in detail. The Smalltalk-80 language is studied first, leading to an explication of both the major subtleties inherent in the problem and the picayune but crippling difficulties with Smalltalk itself which render static analysis in that language ugly and, ultimately, impracticable. An approach to the problem and a new perspective on late-binding itself eventually emerge and, in the final part of the talk, these are applied to the design of a small, late-bound, polymorphic language. I have constructed formal semantics and a provably-sound system for type-inference in this language. These in turn have led to a type-assignment algorithm based on circular unification. P. Curtis, Cornell University Host: J. Williams ------------------------------ Date: 2 Apr 1985 1621-EST From: Lydia Defilippo <DEFILIPPO@CMU-CS-C.ARPA> Subject: Seminar - Inclusive Predicate Existence (CMU) APPLIED LOGIC SEMINAR Speaker: Ketan Mulmuley Date: Monday, April 8, 1985 Time: 2:00 - 3:15 pm Place: 2105 Doherty Hall Title: A Mechanizable Theory For Inclusive Predicate Existence ABSTRACT: In denotational semantics inclusive predicates play a major role in showing the equivalence of two semantics - one operational and one denotational, for example - of a given language. Proving the existence these inclusive predicates is always the hardest part of any semantic equivalence proof. Reynolds and Milne gave a general scheme for proving such existences. However, because of the difficult nature of these proofs it soon became desirable to have a mechanizable theory for such proofs so that the computer could automate a large chunk of them. We shall present one such theory and see how it was implemented on top of LCF. Moreover, we shall prove that this existence issue is indeed nontrivial through diagonalization. ------------------------------ Date: Sun 7 Apr 85 13:23:27-CST From: CL.SHANKAR@UTEXAS-20.ARPA Subject: Seminar - The LCF Programmable Theorem Provers (UTexas) Larry Paulson (Cambridge U.) on LCF, Tue April 9, 4-5pm, Pai 3.02 Abstract: The LCF project has produced a family of interactive, programmable theorem-provers, particularly intended for verifying computer hardware and software. The introduction sketches basic concepts: the metalanguage ML, the logic PPLAMBDA, backwards proof, rewriting, and theory construction. A historical section surveys some LCF proofs. Several proofs involve denotational semantics, notably for compiler correctness. Functional programs for parsing and unification have been verified. Digital circuits have been proved correct, and some subsequently fabricated. There is an extensive bibliography of work related to LCF. The most dynamic issues at present are data types, subgoal techniques, logics of computation, and the development of ML. ------------------------------ Date: 15 Apr 1985 0912-EST From: Lydia Defilippo <DEFILIPPO@CMU-CS-C.ARPA> Subject: Seminar - Automated Programming (CMU) Speakers: Kent Petersson and Jan Smith Dept. of Mathematics, Univ. of Goteborg, Sweden Date: Tuesday, April 16 Time: 3:30 - 4:30 Place: 4605 Wean Hall Topic: Program derivation in type theory In Martin-Lof's type theory, programs can be formally derived from specifications. When formulating a specification, predicate logic is available by the interpretation of propositions as types. Formulating the rules as tactics, programs are constructed "top down." These ideas will be illustrated by a derivation of a program for the partitioning problem. ------------------------------ Date: 17 Apr 85 13:28:24 EST From: John <Bresina@RUTGERS.ARPA> Subject: Seminar - Mathematical Discovery and Hindsight (RU) Machine Learning Colloquium MATHEMATICAL DISCOVERY AND THE HINDSIGHT CRITERION Michael Sims, Rutgers Abstract My dissertation research is an investigation into the nature of mathematical discovery, and this talk will concern the portion of that work related to the understanding of the relationship between changes in representation and a discovery systems performance. More specifically, I would like to define new concepts in such a way that the resulting representation language leads to better efficiency in future discovery tasks. I will suggest a general principle (Hindsight Criterion), which leads to greater future efficiency in concept formation problems in an interestingness driven discovery system. I will also indicate why this is expected to be true. The Hindsight Criterion says that it is useful to define a new concept when doing so will make an (already known) interesting expression simpler. Although this is a widely used criterion, my work indicates how Hindsight relates to the complexity of the search for the original expression, as well as how it can improve the complexity of future discoveries in an actual discovery system. I will also discuss how Hindsight is being used to direct concept formation in the mathematical discovery system, IL, which I am currently implementing. DATE: Friday, April 19th TIME: 11:00-12noon (talk); 12noon-12:30 (discussion) PLACE: Room 423, Hill ------------------------------ Date: 25 Apr 1985 0828-EST From: Lydia Defilippo <DEFILIPPO@CMU-CS-C.ARPA> Subject: Seminar - Foundations of Horn Logic Programming (CMU) Speaker: Vijay Saraswat Date: Monday, April 29, 1985 Time: 2:00 - 3:15 Place: Scaife Hall 324 Topic: On the foundations of (Horn) logic programming. In this talk I present the classical (van Emden, Kowalski, Apt ...) interpretation of Horn logic (without equality) as a programming language. In this view (computation as deduction), definite clauses are viewed as specifications of recursively defined procedures. The least fixed point of the functional associated with these procedures (which can be captured by a form of resolution known as SLD-resolution, i.e. non-deterministic procedure call with parameter passing by unification) is then seen as precisely the extension of the corresponding predicate in the initial model of the axioms. Various operational notions of "negation" arise in this context, which can be related to validity in certain Herbrand models, and I will discuss them briefly. I will also discuss recent work by Nait-Abdallah and van Emden on the semantics of a certain kind of infinitary computation using Horn clauses. Finally, I will touch upon some "real" "logic" programming langauges such as Prolog and Concurrent Prolog and show why the classical semantics is not adequate. For Prolog it only provides a notion of partial correctness, and for Concurrent Prolog it just bounds the space of correct answers to a query, while not telling us anything about whether the query might fail or not terminate. Answering such questions leads to the application of more conventional techniques from semantics of programming languages to (Horn) logic programming. ------------------------------ Date: Wed 24 Apr 85 17:10:00-PST From: Emma Pease <Emma@SU-CSLI.ARPA> Subject: Seminar - Property Theory and Second-Order Logic (CSLI) [Excerpted from the CSLI Newsletter by Laws@SRI-AI.] THURSDAY, May 2, 1985 2:15 p.m. CSLI Seminar Redwood Hall ``Property Theory and Second-Order Logic'' Room G-19 Chris Menzel, CSLI ``Property Theory and Second-Order Logic'' Much recent work in semantics (e.g., Barwise and Perry, Chierchia, Sells, Zalta) involves an extensive appeal to abstract logical objects--properties, relations, and propositions. Such objects were of course not unheard of in semantics prior to this work. What is noteworthy is the extent to which the conception of these objects differs from the prevailing conception in formal semantics, viz., Montague's. Two ways in which they differ (not necessarily common to all recent accounts) stand out: first, these abstract objects are metaphysically primitive, not set theoretic constructions out of possible worlds and individuals; second, they are untyped--properties can exemplify each other as well as themselves, relations can fall within their own field, and so on. With properties, relations, and propositions playing this more prominent role in semantics (as well as in philosophy), it is essential that there be a rigorous mathematical theory of these objects. The framework for such a theory, I think, is second-order logic; indeed, I will argue that second-order logic, rightly understood, just IS the theory of properties, relations, and propositions. To this end, building primarily on the work of Bealer, Cocchiarella, and Zalta, I will present a second-order logic that is provably consistent along with an algebraic intensional semantics which yields significant insights into the structure of the abstract ontology of logic and the paradoxes. Time permitting, I will apply the logic to two issues, one in semantics and the other in the philosophy of mathematics--specifically, to the analysis of noun phrases involving terms of order like `fourth' and `last', and the question of what the (ordinal) numbers are, to which I will give a logicist answer adumbrated by Russell. --Chris Menzel ------------------------------ End of AIList Digest ********************