We consider a fully SAT-based method of unbounded symbolic model checking based on computing Craig interpolants. In benchmark studies using a set of large industrial circuit verification instances, this method is greatly more efficient than BDD-based symbolic model checking, and compares favorably to some recent SAT-based model checking methods on positive instances.

Interpolation and SAT-based model checking

Nowadays, numerous journals and conferences have published articles related to context-aware systems, indicating many researchers' interest. Therefore, the goal of this paper is to review the works that were published in journals, suggest a new classification framework of context-aware systems, and explore each feature of classification framework. This paper is based on a literature review of context-aware systems from 2000 to 2007 using a keyword index and article title search. The classification framework is developed based on the architecture of context-aware systems, which consists of the following five layers: concept and research layer, network layer, middleware layer, application layer and user infrastructure layer. The articles are categorized based on the classification framework. This paper allows researchers to extract several lessons learned that are important for the implementation of context-aware systems.

Context-aware systems

Object-oriented programming languages allow inter-object aliasing. Although necessary to construct linked data structures and networks of interacting objects, aliasing is problematic in that an aggregate object's state can change via an alias to one of its components, without the aggregate being aware of any aliasing.Ownership types form a static type system that indicates object ownership. This provides a flexible mechanism to limit the visibility of object references and restrict access paths to objects, thus controlling a system's dynamic topology. The type system is shown to be sound, and the specific aliasing properties that a system's object graph satisfies are formulated and proven invariant for well-typed programs.

/pdf/ownership-types-for-flexible-alias-protection-em0qfq0odr.pdf

Ownership types for flexible alias protection

The Art of Multiprocessor Programming

Stephen J. Hartley Oxford University Press, New York, 1998, 260 pp. ISBN 0-19-511315-2, $45.00 Concurrent Programming  is a thorough treatment of Java multi-threaded programming for both a stand-alone and distributed environment. Designed mostly for students in concurrent or parallel programming classes, the text is also an excellent reference for the practicing professional developing multi-threaded programs or applets. Hartley first provides a complete explanation of the features of Java necessary to write concurrent programs, including topics such as exception handling, interfaces, and packages. He then gives the reader a solid background to write multi-threaded programs and also presents the problems introduced when writing concurrent programs—namely race conditions, mutual exclusion, and deadlock. Hartley also provides several software solutions that do not require the use of common process and thread mechanisms. Once the groundwork is laid for writing concurrent programs, Hartley then takes a different approach than most Java references. Rather than presenting how Java handles mutual exclusion with the  synchronized  keyword (although it is covered later), he first looks at semaphore-based solutions to classic concurrent problems such as bounded-buffer, readers-writers, and the dining philosophers. Hartley also uses the same approach to develop Java classes for monitors and message passing. This unique approach to introducing concurrency allows the readers to both understand how Java threads are synchronized and how the basic synchronization mechanism can be used to construct more abstract tools such as semaphores. If there is a shortcoming with the text it is with the lack of sufficient coverage of remote method invocation (RMI), although there is a section covering RMI. This is quite understandable as RMI is a fairly recent phenomenon with the Java community. Also, the classes that Hartley provides could easily implement RMI rather than sockets to handle communication. The strengths of the book include its ease in reading, several examples at the end of chapters, a package similar to Xtango that provides algorithm animation, and a supportive web site by the author (see  www.mcs.drexel.edu/~shartley/ConcProgJava/index.html ) including compressed source code. As Java becomes more dominant on the server side of multi-tier applications, writing thread-safe concurrent applications becomes even more important.  Concurrent Programming  is a strong step towards teaching students and professionals such skills. Greg Gagne, Westminster College of Salt Lake City Salt Lake City, Utah

Distributed Computing: Fundamentals, Simulations and Advanced Topics

Semantic Space is a pervasive computing infrastructure that exploits semantic Web technologies to support explicit representation, expressive querying, and flexible reasoning of contexts in smart spaces.

http://www-public.tem-tsp.eu/~zhang_da/pub/ieee04pervasive.pdf

Semantic Space: an infrastructure for smart spaces

Recent development on distributed systems has shown that a variety of fairness constraints (some of which are only recently defined) play vital roles in designing self-stabilizing population protocols. Current practice of system analysis is, however, deficient under fairness. In this work, we present PAT, a toolkit for flexible and efficient system analysis under fairness. A unified algorithm is proposed to model check systems with a variety of fairness effectively in two different settings. Empirical evaluation shows that PAT complements existing model checkers in terms of fairness. We report that previously unknown bugs have been revealed using PAT against systems functioning under strong global fairness.

/pdf/pat-towards-flexible-verification-under-fairness-4fszl66tuw.pdf

PAT: Towards Flexible Verification under Fairness

Object-Z is an extension to the Z language designed to facilitate specification in an object-oriented style. It is an excellent tool for modeling data and algorithms, but its object semantics are single threaded and operations are atomic. Therefore, it is difficult to use Object-Z to capture the behaviour of concurrent real-time reactive systems. On the other hand, Timed CSP is good at modeling real-time concurrent behaviour, but has little support for modeling the state of a complex system. This paper introduces a blending of Object-Z and Timed CSP, known as TCOZ. The blended notation is particularly suited for specifying complex systems whose components have their own thread of control.

Blending Object-Z and Timed CSP: an introduction to TCOZ

FDR, initially introduced decades ago, is the de facto analyzer for Communicating Sequential Processes (CSP). Model checking techniques have been evolved rapidly since then. This paper describes Pat, i.e., a process analysis toolkit which complements FDR in several aspects. Pat is designed to analyze event-based compositional system models specified using CSP as well as shared variables and asynchronous message passing. It supports automated refinement checking, model checking of LTL extended with events, etc. In this paper, we highlight how partial order reduction is applied to improve refinement checking in Pat. Experiment results show that Pat outperforms FDR in some cases.

https://ink.library.smu.edu.sg/cgi/viewcontent.cgi?article=6053&context=sis_research

Model Checking CSP Revisited: Introducing a Process Analysis Toolkit

This paper describes a timed, multithreaded object modeling notation for specifying real-time, concurrent, and reactive systems. The notation Timed Communicating Object Z (TCOZ) builds on Object Z's strengths in modeling complex data and algorithms, and on Timed CSP's strengths in modeling process control and real-time interactions. TCOZ Is novel in that it includes timing primitives, properly separates process control and data/algorithm issues and supports the modeling of true multithreaded concurrency. TCOZ is particularly well-suited for specifying complex systems whose components have their own thread of control. The expressiveness of the notation is demonstrated by a case study in specifying a multilift system that operates in real-time.

/pdf/timed-communicating-object-z-4b62jo4fk2.pdf

Jin Song Dong

Papers

Semantic Space: an infrastructure for smart spaces

PAT: Towards Flexible Verification under Fairness

Blending Object-Z and Timed CSP: an introduction to TCOZ

Model Checking CSP Revisited: Introducing a Process Analysis Toolkit

Timed Communicating Object Z