Richard E. Ladner

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We introduce a fundamental propositional logical system based on modal logic for describing correctness, termination and equivalence of programs. We define a formal syntax and semantics for the propositional dynamic logic of regular programs and give several consequences of the definition. Principal conclusions are that deciding satisfiability of length n(More)
Active learning differs from “learning from examples” in that the learning algorithm assumes at least some control over what part of the input domain it receives information about. In some situations, active learning is provably more powerful than learning from examples alone, giving better generalization for a fixed number of training examples. In this(More)
The prefix problem is to compute all the products x t o x2 . . . . o xk for i ~ k .~ n, where o is an associative operation A recurstve construction IS used to obtain a product circuit for solving the prefix problem which has depth exactly [log:n] and size bounded by 4n An application yields fast, small Boolean ctrcmts to simulate fimte-state transducers.(More)
The computational complexity of the provability problem in systems of modal proposi-tional logic is investigated. Every problem computable in polynomial space is log space reducible to the provability problem in any modal system between K and $4. In particular, the provability problem in K, T, and $4 are log space complete in polynomial space. The(More)
Two notions of polynomml time reduclbihty, denoted here by ~ T e and <.~P, were defined by Cook and Karp, respectively The abstract propertms of these two relatmns on the domain of computable sets are investigated. Both relations prove to be dense and to have minimal pairs. Further , there is a strictly ascending sequence with a minimal pair of upper bounds(More)
We present the unequal loss protection (ULP) framework in which unequal amounts of forward error correction are applied to progressive data to provide graceful degradation of image quality as packet losses increase. We develop a simple algorithm that can find a good assignment within the ULP framework. We use the set partitioning in hierarchical trees coder(More)
&tract. Various forms of polynomial time reducibilig:y zwe compared. Among the forms examined we many-one, bounded truth table, truth 1:able and Turing reducibi!&y. The effect of introducing nondeterminism into red " ,ztiGn procedures is also examined. Computation bounded reducibilities play a role in t theory of' ssralputationa~ complexity which is(More)
We consider the problem of fairly matching the left-hand vertices of a bipartite graph to the right-hand vertices. We refer to this problem as the optimal semimatching problem; it is a relaxation of the known bipartite matching problem. We present a way to evaluate the quality of a given semi-matching and show that, under this measure, an optimal(More)