Extending the theory of Owicki and Gries with a logic of progress

This paper describes a logic of progress for concurrent programs. The logic is based on that of UNITY, molded to fit a sequential programming model. Integration of the two is achieved by using auxiliary variables in a systematic way that incorporates program counters into the program text. The rules for progress in UNITY are then modified to suit this new system. This modification is however subtle enough to allow the theory of Owicki and Gries to be used without change.

Formalising progress properties of non-blocking programs

A non-blocking program is one that uses non-blocking primitives, such as load-linked/store-conditional and compare-and-swap, for synchronisation instead of locks so that no process is ever blocked. According to their progress properties, non-blocking programs may be classified as wait-free, lock-free or obstruction-free. However, a precise description of these properties does not exist and it is not unusual to find a definition that is ambiguous or even incorrect. We present a formal definition of the progress properties so that any confusion is removed. The formalisation also allows one to prove the widely believed presumption that wait-freedom is a special case of lock-freedom, which in turn is a special case of obstruction-freedom.

A partial-correctness semantics for modelling assembler programs

Previous work on formally modelling and analysing program compilation has shown the need for a simple and expressive semantics for assembler level programs. Assembler programs contain unstructured jumps and previous formalisms have modelled these by using continuations, or by embedding the program in an explicit emulator. We propose a simpler approach, which uses techniques from compiler theory in a formal setting. This approach is based on an interpretation of programs as collections of program paths, each of which has a weakest liberal precondition semantics. We then demonstrate, by example, how we can use this formalism to justify the compilation of block-structured high-level language programs into assembler.

Trace Semantics for the Owicki-Gries Theory Integrated with the Progress Logic from UNITY

The theory of Owicki and Gries has been used as a platform for safety-based verifcation and derivation of concurrent programs. It has also been integrated with the progress logic of UNITY which has allowed newer techniques of progress-based verifcation and derivation to be developed. However, a theoretical basis for the integrated theory has thus far been missing. In this paper, we provide a theoretical background for the logic of Owicki and Gries integrated with the logic of progress from UNITY. An operational semantics for the new framework is provided which is used to prove soundness of the progress logic.

Proof Explanation in the DR-DEVICE System

Trust is a vital feature for Semantic Web: If users (humans and agents) are to use and integrate system answers, they must trust them. Thus, systems should be able to explain their actions, sources, and beliefs, and this issue is the topic of the proof layer in the design of the Semantic Web. This paper presents the design and implementation of a system for proof explanation on the Semantic Web, based on defeasible reasoning. The basis of this work is the DR-DEVICE system that is extended to handle proofs. A critical aspect is the representation of proofs in an XML language, which is achieved by a RuleML language extension.

Embedding defeasible logic into logic programming

Defeasible reasoning is a simple but efficient approach to nonmonotonic reasoning that has recently attracted considerable interest and that has found various applications. Defeasible logic and its variants are an important family of defeasible reasoning methods. So far no relationship has been established between defeasible logic and mainstream nonmonotonic reasoning approaches. In this paper we establish close links to known semantics of logic programs. In particular, we give a translation of a defeasible theory D into a meta-program P(D). We show that under a condition of decisiveness, the defeasible consequences of D correspond exactly to the sceptical conclusions of P(D) under the stable model semantics. Without decisiveness, the result holds only in one direction (all defeasible consequences of D are included in all stable models of P(D)). If we wish a complete embedding for the general case, we need to use the Kunen semantics of P(D), instead.

Compilation by refinement for a practical assembly language

In this paper we extend the conventional framework of program refinement down to the assembler level. We describe an extension to the Refinement Calculus that supports the refinement of programs in the Guarded Command Language to programs in .NET assembler. This is illustrated by a small example.

ADHD and medicalization: consideration of the senses and meanings of symptoms presented by children diagnosed

The present paper is a reflection on the diagnosis of Attention Deficit Hyperactivity Disorder (ADHD) and its relations to the process of medicalization as well as the meanings and perspectives apprehended through three case studies of children diagnosed with such disorder in a doctoral research in which the main purpose was to understand the meanings and peculiarities of ADHD symptomatology .We’ve utilized the model of qualitative research, grounded in psychoanalytic perspective, and conducted the psychodiagnosis for three children who were referred for psychological treatment. The survey found that those children had few experiences of both continence and frustration tolerance. It was evidenced how the school uses the logic of medicalization to try solving the problems with their children when it came to the school dimension. The variety of symptomatic manifestations and psychic dynamics presented by the cases that were studied revealed the weaknesses and inconsistencies of the referred diagnosis.

"Framing Counterspaces: Forms and Meanings of Graffiti in Berlin's Linguistic Landscape"

Street art and graffiti are integral parts of Berlin’s urban space, which has undergone dramatic transformations in the past two decades. Graffiti texts constitute a critical comment on these urban transformations. This talk analyzes the connection between the phenomenon of street art and trajectories in urban planning in post-wall Berlin. My current research explores the meaning of various forms of street art (such as graffiti, posters, sticker art, stencils) as texts in Berlin’s linguistic landscape. Linguistic Landscape research pays critical attention to language, words, and images displayed and exposed in public spaces. The field of Linguistic Landscapes has only recently begun to include graffiti texts in analyses of text and space to fully comprehend the semiotics of the street. In the case of Germany’s capital, graffiti writing enters into a critical dialogue with the environment and provides a readable text to understand the city.