A simple dynamic logic
A system of dynamic predicate logic is presented. It allows nonstandard modelling of time, which makes recursive axiomatization possible, and is essentially one-sorted (the same elements code data and time), which makes the system reasonably simple and transparent. The system is subjected to usual mathematical considerations; in particular, it is shown to be equivalent to the three-sorted system due to Andreka, Nemeti and Sain (1982). A conservation result for the latter system is obtained as a by-product.

title: Fuzzy Logic and Arithmetical Hierarchy, II
abstract: A very simple many-valued predicate calculus is presented; a completeness theorem is proved and the arithmetical complexity of some notions concerning provability is determined.

title: Logics of Knowing and Believing
abstract: What is the relation of intelligence (natural or artificial) to logic? This is surely a fascinating question with many aspects. We shall not discuss what intelligence is; but we shall start by saying that logic is understood as the study of consequence and of deduction as obtaining consequences from (accepted, assumed) premises (axioms). It goes without saying that intelligence has a logical aspect (among various other aspects). Intelligent systems are said to work with various sorts of knowledge; knowledge representation and processing, and even reasoning about knowledge are considered to be important topics in AI. Knowledge may be uncertain; thus one has to work with beliefs. It has turned out that logical aspects of reasoning about knowledge and beliefs are well formalized by means of some systems of modal logic called logic of knowledge and of belief respectively. An excellent survey of propositional (Boolean) logics of knowledge and belief in relation to computational complexity (with full proofs of main results) is given by Halpern (1992). Most basic facts on these logics are surveyed in Sect. 2 of this chapter. Section 3 surveys basic facts on predicate (Boolean) logics of knowledge and belief; Hughess and Cresswell (1984) contains details. The main part is Sect. 4 where we take into consideration the fact that most knowledge in AI systems (not speaking about natural intelligence) is imprecise (vague, fuzzy), which leads us to fuzzy logic.

title: Trakhtenbrot Theorem and Fuzzy Logic
abstract: Trakhtenbrot theorem is shown to be valid for the three main fuzzy logics – Łukasiewicz, Godel and product logic.

title: Metamathematics of Fuzzy Logic
abstract: Preface. 1. Preliminaries. 2. Many-Valued Propositional Calculi. 3. Lukasiewicz Propositional Logic. 4. Product Logic, Godel Logic. 5. Many-Valued Predicate Logics. 6. Complexity and Undecidability. 7. On Approximate Inference. 8. Generalized Quantifiers and Modalities. 9. Miscellanea. 10. Historical Remarks.

title: Arithmetical Interpretations of Dynamic Logic
abstract: An arithmetical interpretation of dynamic propositional logic (DPL) is a mapping f satisfying the following: (1) fassociates with each formula A of DPL a sentencef(A) of Peano arithmetic (PA) and with each program a a formula f(a) of PA with one free variable describing formally a supertheory of PA; (2) f commutes with logical connectives; (3) f([aK]A) is the sentence saying that f(A) is provable in the theory f(a); (4) for each axiom A of DPL, f(A) is provable in PA (and consequently, for each A provable in DPL, f(A) is provable in PA). The arithmetical completeness theorem is proved saying that a formula A of DPL is provable in DPL iff for each arithmetical interpretationf,f(A) is provable in PA. Various modifications of this result are considered.  The aim of the present paper is to apply techniques of arithmetical interpretations (or: provability interpretations) of modal propositional logic (as developed and studied by deJongh, Sambin, Solovay, Smoryn'ski, Guaspari and others, see ,  ) to dynamic logic. Dynamic logic (or: logic of programs) is a generalization of modal logic extensively studied in computer science (Pratt, Fischer, Ladner, Segerbergh, Parikh, see , , ). Both various systems of modal logic and systems of dynamic logic have well-behaving Kripke semantics (necessity means validity in all alternative states-worlds) and complete axiomatizations (for modal logic see [6] and , for dynamic logic see ). The idea behind arithmetical interpretations of modal logic is to interpret necessity as formal provability (in arithmetic). Now, dynamic logic is a modal logic with many modalities of necessity (corresponding to programs) so that the question arises whether one could interpret these modalities by formal provability in various theories (and obtain some completeness results). This question will be answered positively. What is the meaning of our results? First, the question just formulated seems to be a very natural question and it seems not to be trivial to answer it. Second, our result could elucidate from an unexpected point of view the saying of Kowalski : "algorithm logic + control". We shall see that programs (algorithms)i.e. their logical components-may be modelled by some formal theories. Third, it has proved to be useful to investigate modal calculi having various modalities, not just the necessity, when studying self-reference in Peano arithmetic ((see [10], ). And we have in dynamic logic an example of such a calculus having both Received October 15, 1981. ? 1983, Association for Symbolic Logic 0022-4812/83/4803-0021 /$02.00

title: Polynomial algebras on classical banach spaces
abstract: For the classical Banach spacesX = ℓp,C(K) we identify alln such that every polynomial of degreen + 1 onX is uniformly approximable on the unit ball by elements of the algebra generated by all polynomials of degree up ton onX.

title: Analytic Renormings of C(K) Spaces
abstract: A ladder system is disposed between two spaced storage shelves. The ladder may move longitudinally along the shelves, and may also be moved laterally between the shelves. Further, the ladder may pivot about a lateral axis such that the ladder may be picked up over obstructions in an aisle between the shelves. In this way, one can quickly and easily position the ladder at any position along or between the two storage shelves for accessing items stored on the shelves. This ladder system is particularly useful in the crowded warehouse-type retail outlets which are now gaining popularity.

title: Dual renormings of Banach spaces
abstract: We prove that a Banach space admitting an equivalent WUR norm is an Asplund space. Some related dual renormings are also presented.

title: Smooth norms that depend locally on finitely many coordinates
abstract: We characterize separable normed spaces that admit equivalent COO-smooth norms depending locally on finitely many coordinates. It follows, in particular, that such norms exist on any normed space with countable algebraic basis. We use the method of Talagrand operators developed by Haydon in  and certain integral convolution techniques [2], [13] to characterize separable normed spaces that admit C??-smooth norms depending locally on finitely many coordinates as spaces that admit norms with countable boundaries. As corollaries we obtain improvements on some results of Fonf  and Vanderwerff  and a new simple proof of a result of Haydon on Cw-smooth renormings of spaces of continuous functions on countable compact sets. Our results should be compared to the result of Godun, Lin, and Troyanski in  where it is shown that every separable Banach space can be given an equivalent norm, the unit ball of which contains countably many strongly extreme points. From this result and Theorem 1 below it follows that strongly extreme points need not necessarily form a boundary of Bx* . We will use the notation standard in Banach space theory. In particular, Bx and Sx will denote respectively the unit ball and the unit sphere of a Banach space X. We say that 11 11 depends locally on finitely many coordinates if for each x E Sx there exist an open neighbourhood 0 of x, a finite set {x, ...,Xk*} C X*, and a function f: Rk -+ R such that IIYII =f(X1*(y), ...,xk*(y)) fory EO. If (X, 11) is a normed space, the set B c Sx* is called a boundary of (X, * 11) if for each x E Sx there exists x* E B such that x*(x) = 1. Theorem 1. Let (X, 11 * 11) be a normed space.  (i) X admits an equivalent norm having a countable boundary. (ii) X admits an equivalent norm with a boundary B, such that there is a sequence {Kn}nEN of norm compact sets in X* satisfing B C UnEN KnX Received by the editors October 13, 1993 and, in revised form, June 15, 1994.