Refining SCJ Mission Specifications into Parallel Handler Designs

Safety-Critical Java (SCJ) is a recent technology that restricts the execution and memory model of Java in such a way that applications can be statically analysed and certified for their real-time properties and safe use of memory. Our interest is in the development of comprehensive and sound techniques for the formal specification, refinement, design, and implementation of SCJ programs, using a correct-by-construction approach. As part of this work, we present here an account of laws and patterns that are of general use for the refinement of SCJ mission specifications into designs of parallel handlers used in the SCJ programming paradigm. Our notation is a combination of languages from the Circus family, supporting state-rich reactive models with the addition of class objects and real-time properties. Our work is a first step to elicit laws of programming for SCJ and fits into a refinement strategy that we have developed previously to derive SCJ programs.Comment: In Proceedings Refine 2013, arXiv:1305.563

SCJ-Circus : a refinement-oriented formal notation for Safety-Critical Java

Safety-Critical Java (SCJ) is a version of Java whose goal is to support the development of real-time, embedded, safety-critical software. In particular, SCJ supports certification of such software by introducing abstractions that enforce a simpler architecture, and simpler concurrency and memory models. In this paper, we present SCJ-Circus, a refinement-oriented formal notation that supports the specification and verification of low-level programming models that include the new abstractions introduced by SCJ. SCJ-Circus is part of the family of state-rich process algebra Circus, as such, SCJ-Circus includes the Circus constructs for modelling sequential and concurrent behaviour, real-time and object orientation. We present here the syntax and semantics of SCJ-Circus, which is defined by mapping SCJ-Circus constructs to those of standard Circus. This is based on an existing approach for modelling SCJ programs. We also extend an existing Circus-based refinement strategy that targets SCJ programs to account for the generation of SCJ-Circus models close to implementations in SCJ

SCJ-Circus: specification and refinement of Safety-Critical Java programs

Safety-Critical Java (SCJ) is a version of Java for real-time, embedded, safety-critical applications. It supports certification via abstractions that enforce a particular program architecture, with controlled concurrency and memory models. SCJ is an Open Group standard, with a reference implementation, but little support for reasoning. Here, we present SCJ-Circus, a refinement notation for specification and verification of low-level models of SCJ programs. SCJ-Circus is part of the Circus family of state-rich process algebras: it includes the Circus constructs for modelling of sequential and concurrent behaviour based on Z and CSP, and the real-time and object-oriented extensions of Circus, in addition to the SCJ abstractions. We present the syntax of SCJ-Circus and its semantics, defined by mapping SCJ-Circus constructs to those of Circus. We also detail a refinement strategy that takes a Circus design that adheres to a multiprocessor cyclic executive pattern and produces an SCJ program design, described in SCJ-Circus. Finally, we show how this refinement strategy can be extended for more complex program architectures

Bilateral Asymmetrical Traumatic Sternoclavicular Joint Dislocations

Unilateral and bilateral sternoclavicular joint (SCJ) dislocations are rare injuries. The difficulty in assessing this condition often leads to delay in diagnosis and treatment. We report a rare case of bilateral asymmetrical traumatic SCJ dislocations in a 45-year-old male. The right anterior SCJ dislocation was reduced in the emergency room (ER) and resulted in residual instability. The left posterior SCJ dislocation was asymptomatic and unnoticed for six months. It is important for ER physicians and orthopaedic surgeons to be able identify and treat this condition. All suspected SCJ dislocations should be evaluated by computed tomography (CT) scan for confirmation of the diagnosis and evaluation of both SCJs. Posterior SCJ dislocation is a potentially fatal injury and should not be overlooked due to the presence of other injuries. Surgical intervention is often necessary in acute and old cases

Safety-Critical Java on a Java Processor

The safety-critical Java (SCJ) specification is developed within the Java Community Process under specification request number JSR 302. The specification is available as public draft, but details are still discussed by the expert group. In this stage of the specification we need prototype implementations of SCJ and first test applications that are written with SCJ, even when the specification is not finalized. The feedback from those prototype implementations is needed for final decisions. To help the SCJ expert group, a prototype implementation of SCJ on top of the Java optimized processor is developed and presented in this paper. This implementation raises issues in the SCJ specification and provides feedback to the expert group

Evaluating Future Dangerousness and Need for Treatment: The Roles of Expert Testimony, Attributional Complexity, and Victim Type

In the current study, we explored the effect of risk-assessment testimony, attributional complexity, and victim type on participants’ perceptions of the dangerousness of a sexually violent person and his need for treatment. Participants read details of a hypothetical sexual assault of a female minor and of an adult. Expert testimony of his risk assessment consisted of clinical opinion versus structured-clinical judgment (SCJ) versus actuarial assessment. Participants perceived clinical-opinion and SCJ testimony as equally influential when forming judgments of future dangerousness. In the context of treatment, however, participants relied on actuarial testimony when judging potential for risk. In addition, attributional complexity (AC) moderated perceptions of sexual risk. Overall, results point to the need for continued refinement of assessment techniques when determining dangerousness and need for treatment

Effect of Sugar Cane Juice on Slump Values, Setting Times and Strength of Concrete

The effect of sugar cane juice, (SCJ) on slump values, setting time and compressive strength of concrete cubes was investigated. A total of 32 concrete cubes of size 150x150x150mm with a mix ratio of 1:2:4 were cast with different percentages of unfermented sugar cane juice replacing some proportion of water in the concrete mix. Water/Sugar Cane Juice/cement ratio was held constant at 0.45. The concrete cubes were prepared by replacing water with SCJ in the following proportions 0, 25, 50 and 100%. The cubes were cured, tested and the physical properties of interest in this study were determined. The slump values of the concrete decreased from 40mm at 100: 0 (water:SCJ) to 18mm at 50:50 (water:SCJ) and to 0mm (collapse) at (0:100) (water :SCJ). The final setting time of concrete increased with increase in proportion of SCJ. The highest final setting time of 42 hours (considered excessive), occurred at 75:25 (water:SCJ) proportion. The compressive strength of the (water:SCJ) concrete decreased as the percentage of SCJ increased up to 25% SCJ. Thereafter, an increase in compressive strength was noticed up till 100% SCJ, with a maximum strength of 13.08N/mm2 occurring at 100% SCJ at 28 days. The early strength reduction is due to quick-setting of the concrete, at 25% SCJ, retardation commences and the strength of concrete increases. The study has been carried out at 0, 25, 50 and 100% replacement by weight of potable water with SCJ. A comparative study has been done between concrete made with potable water and those made with water/sugar cane juice.http://dx.doi.org/10.4314/njt.v34i2.

Circus Models for Safety-Critical Java Programs

Safety-critical Java (SCJ) is a restriction of the real-time specification for Java to support the development and certification of safety-critical applications. The SCJ technology specification is the result of an international effort from industry and academia. In this paper, we present a formalization of the SCJ Level 1 execution model, formalize a translation strategy from SCJ into a refinement notation and describe a tool that largely automates the generation of the formal models. Our modelling language is part of the Circus family; at the core, we have Z, communicating sequential processes and Morgan’s calculus, but we also use object-oriented and timed constructs from the OhCircus and Circus Time variants. Our work is an essential ingredient for the development of refinement-based reasoning techniques for SCJ

Memory Management for Safety-Critical Java

Safety-Critical Java (SCJ) is based on the Real-Time Specification for Java. To simplify the certification of Java programs, SCJ supports only a restricted scoped memory model. Individual threads share only immortal memory and the newly introduced mission memory. All other scoped memories are thread private. Furthermore, the notation of a maximum backing store requirement enables implementation of the scoped memories without fragmentation issues. In this paper we explore the implications of this new scoped memory model and possible simplifications in the implementation. It is possible to unify the three memory area types and provide a single class to represent all three memory areas of SCJ. The knowledge of the maximum storage requirements allows using nested backing stores in the implementation of the memory area representation. The proposed design of an SCJ compliant scope implementation is evaluated on an embedded Java processor