Towards a Denotational Semantics of Timed RSL Using Duration Calculus

The Timed RAISE Specification Language (Timed RSL) is an extension of RAISE Specification Language by adding time constructors for specifying real-time applications. Duration Calculus (DC) is a real-time interval logic, which can be used to specify and reason about timing and logical constraints on dura- tion properties of Boolean states in a dynamic system. This paper gives a denotational semantics to a subset of Timed RSL expressions, using Duration Calculus extended with super-dense chop modality and notations to capture time point properties of piecewise continuous states of arbitrary types. Using this semantics, the paper presents a proof rule for verifying Timed RSL iterative expressions and implements the rule to prove the satisfaction by a sample Timed RSL specification of its real-time requirements.

Semantic theories of programs with nested interrupts

In the design of dependable software for embed- ded and real-time operating systems, time analysis is a cru- cial but extremely difficult issue, the challenge of which is exacerbated due to the randomness and nondeterminism of interrupt handling behaviors. Thus research into a theory that integrates interrupt behaviors and time analysis seems to be important and challenging. In this paper, we present a pro- gramming language to describe programs with interrupts that is comprised of two essential parts： main program and inter- rupt handling programs. We also explore a timed operational semantics and a denotational semantics to specify the mean- ings of our language. Furthermore, a strategy of deriving de- notational semantics from the timed operational semantics is provided to demonstrate the soundness of our operational se- mantics by showing the consistency between the derived de- notational semantics and the original denotational semantics.

Modeling and Verifying Concurrent Programs with Finite Chu Spaces

Finite Chu spaces are proposed for the modeling and verification of concurrent programs.In order to model not only typical concurrent behaviors but also modern exception handling and synchronization mechanisms,we design an enriched process algebra of Chu spaces from a practical point of view.To illustrate the power of finite Chu spaces and the process algebra while abstracting away from language-specific details,an imaginary concurrent programming language（ICL） is designed.A denotational semantics of ICL is presented using finite Chu spaces and the enriched process algebra.The valuation functions are fairly straightforward since the carefully designed operators have done much of the job.The enriched process algebra is also used as the specification language for Chu spaces,with which process-algebraic properties can be specified.Verification algorithms are presented with their time complexities discussed.

A UTP semantic model for Orc language with execution status and fault handling

The Orc language is a concurrency calculus pro- posed to study the orchestration patterns in service oriented computing. Its special features, such as high concurrency and asynchronism make it a brilliant subject for studying web applications that rely on web services. The conventional se- mantics for Orc does not contain the execution status of ser- vices so that a program cannot determine whether a service has terminated normally or halted with a failure after it pub- lished some results. It means that this kind of failure cannot be captured by the fault handler. Furthermore, such a seman- tic model cannot establish an order saying that a program is better if it fails less often. This paper employs UTP methods to propose a denotational semantic model for Orc that con- rains execution status information. A failure handling seman- tics is defined to recover a failure execution back to normal. A refinement order is defined to compare two systems based on their execution failures. Based on this order, a system that introduces a failure recovery mechanism is considered bet- ter than one without. An extended operational semantics is also proposed and proven to be equivalent to the denotational semantics.