Subtypes and bounded quantification from a fibred perspective

AbstractA general categorical description of subtyping σ < σ′ and of bounded quantification ∀α<: σ.τ and ∃α <: σ.τ is presented in terms of fibrations. In fact, we shall generalize these bounded quantifiers to “constrained quantifiers” ∀α[σ <: σ′].τ and ∃α[σ <: σ′].τ. In these cases one quantifies over those type variables α for which σ(α) <: σ′(α) holds. Semantically we distinguish three levels: types τ, which are fibered over (depend on) subtypings σ <: σ′, which in turn are fibred over (depend on) kinds K. In this setting we can describe constrained quantification ∀α[σ <: σ′]. (−) and ∃α[σ <: σ′]. (−) as right and left adjoints to the weakening functor which adds the (dummy) hypothesis σ <: σ′ to an appropriate context. This shows that, like ordinary quantifiers, these constrained (and hence especially bounded) quantifiers are adjoints

Statically checking confidentiality via dynamic labels

This paper presents a new approach for verifying confidentiality for programs, based on abstract interpretation. The framework is formally developed and proved correct in the theorem prover PVS. We use dynamic labeling functions to abstractly interpret a simple programming language via modification of security levels of variables. Our approach is sound and compositional and results in an algorithm for statically checking confidentiality

RIES: Internet voting in action

RIES stands for Rijnland Internet Election System. It is an online voting system that was developed by one of the Dutch local authorities on water management. The system has been used twice in the fall of 2004 for in total approximately two million potential voters. In this paper we describe how this system works. Furthermore we do not only describe how the outcome of the elections can be verified but also how it has been verified by us. To conclude the paper we describe some possible points for improvement

Categoral views on computations on trees (Extended abstract)

Computations on trees form a classical topic in computing. These computations can be described in terms of machines (typically called tree transducers), or in terms of functions. This paper focuses on three flavors of bottom-up computations, of increasing generality. It brings categorical clarity by identifying a category of tree transducers together with two different behavior functors. The first sends a tree transducer to a coKleisli or biKleisli map (describing the contribution of each local node in an input tree to the global transformation) and the second to a tree function (the global tree transformation). The first behavior functor has an adjoint realization functor, like in Goguen’s early work on automata. Further categorical structure, in the form of Hughes’s Arrows, appears in properly parameterized versions of these structures

Partial Recursive Functions and Finality

Abstract. We seek universal categorical conditions ensuring the representability of all partial recursive functions. In the category Pfn of sets and partial functions, the natural numbers provide both an initial algebra and a final coalgebra for the functor 1 + −. We recount how finality yields closure of the partial functions on natural numbers under Kleene’s µ-recursion scheme. Noting that Pfn is not cartesian, we then build on work of Paré and Román, obtaining weak initiality and finality conditions on natural numbers algebras in monoidal categories that ensure the (weak) representability of all partial recursive functions. We further obtain some positive results on strong representability. All these results adapt to Kleisli categories of cartesian categories with natural numbers algebras. However, in general, not all partial recursive functions need be strongly representable.

Reasoning about Java classes

Contains fulltext : reasabjac.pdf ( ) (Open Access)20 p

Burger moet geen gelabeld vee worden

Contains fulltext : 36027.pdf (author's version ) (Open Access)17 februari 200

Select before you Collect

Contains fulltext : 32979.pdf (publisher's version ) (Open Access

The temporal logic of coalgebras via Galois algebras

Contains fulltext : 18761_temploofc.pdf ( ) (Open Access)27 p