We show that a type system based on the intuitionistic modal logic S4 provides an expressive framework for specifying and analyzing computation stages in the context of functional languages. Our main technical result is a conservative embedding of Nielson & Nielson's two-level functional language in our language Mini-ML, which in

this paper we reconsider the foundations of modal logic, following MartinL of's methodology of distinguishing judgments from propositions [ML85]. We give constructive meaning explanations for necessity (2) and possibility (3). This exercise yields a simple and uniform system of natural deduction for intuitionistic modal logic which does not exhibit anomalies found in other proposals. We also give a new presentation of lax logic [FM97] and find that it is already contained in modal logic, using the decomposition of the lax modality fl A as

The Concurrent Logical Framework, or CLF, is a new logical framework in which concurrent computations can be represented as monadic objects, for which there is an intrinsic notion of concurrency. It is designed as a conservative extension of the linear logical framework LLF with the synchronous connectives# of intuitionistic linear logic, encapsulated in a monad. LLF is itself a conservative extension of LF with the asynchronous connectives -#, & and #.

We present a constructive authorization logic where the meanings of connectives are defined by their associated inference rules. This ensures that the logical reading of access control policies expressed in the logic and their implementation coincide. We study the proof-theoretic consequences of our design including cut-elimination and two non-interference properties that allow administrators to explore the correctness of their policies by establishing that for a given policy, assertions made by certain principals will not affect the truth of assertions made by others.

We present an authorization logic that permits reasoning with explicit time. Following a proof-theoretic approach, we study the meta-theory of the logic, including cut elimination. We also demonstrate formal connections to proof-carrying authorization’s existing approach for handling time and comment on the enforceability of our logic in the same framework. Finally, we illustrate the expressiveness of the logic through examples, including those with complex interactions between time, authorization, and mutable state.

Abstract. We present a translation from a logic of access control with a “says ” operator to the classical modal logic S4. We prove that the translation is sound and complete. We also show that it extends to logics with boolean combinations of principals and with a “speaks for ” relation. While a straightforward definition of this relation requires second-order quantifiers, we use our translation for obtaining alternative, quantifierfree presentations. We also derive decidability and complexity results for the logics of access control. 1

We consider two systems of constructive modal logic which are computationally motivated. Their modalities admit several computational interpretations and are used to capture intensional features such as notions of computation, constraints, concurrency, etc. Both systems have so far been studied mainly from type-theoretic and category-theoretic perspectives, but Kripke models for similar systems were studied independently. Here we bring these threads together and prove duality results which show how to relate Kripke models to algebraic models and these in turn to the appropriate categorical models for these logics.

Motivated by many practical applications that have to compute in the presence of uncertainty, we propose a monadic probabilistic language based upon the mathematical notion of sampling function. Our language provides a unified representation scheme for probability distributions, enjoys rich expressiveness, and o#ers high versatility in encoding probability distributions. We also develop a novel style of operational semantics called a horizontal operational semantics, under which an evaluation returns not a single outcome but multiple outcomes. We have preliminary evidence that the horizontal operational semantics improves the ordinary operational semantics with respect to both execution time and accuracy in representing probability distributions.

Authorization policies are not stand-alone objects: they are used to selectively permit actions that change the state of a system. Thus, it is desirable to have a framework for reasoning about the semantic consequences of policies. To this end, we extend a rewriting interpretation of linear logic with connectives for modeling affirmation, knowledge, and possession. To cleanly confine semantic effects to the rewrite sequence, we introduce a monad. The result is a richly expressive logic that elegantly integrates policies and their effects. After presenting this logic and its metatheory, we demonstrate its utility by proving properties that relate a simple file system’s policies to their semantic consequences.

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