Optimizing Computation of Recovery Plans for BPEL Applications

Web service applications are distributed processes that are composed of dynamically bounded services. In our previous work [15], we have described a framework for performing runtime monitoring of web service against behavioural correctness properties (described using property patterns and converted into finite state automata). These specify forbidden behavior (safety properties) and desired behavior (bounded liveness properties). Finite execution traces of web services described in BPEL are checked for conformance at runtime. When violations are discovered, our framework automatically proposes and ranks recovery plans which users can then select for execution. Such plans for safety violations essentially involve "going back" - compensating the executed actions until an alternative behaviour of the application is possible. For bounded liveness violations, recovery plans include both "going back" and "re-planning" - guiding the application towards a desired behaviour. Our experience, reported in [16], identified a drawback in this approach: we compute too many plans due to (a) overapproximating the number of program points where an alternative behaviour is possible and (b) generating recovery plans for bounded liveness properties which can potentially violate safety properties. In this paper, we describe improvements to our framework that remedy these problems and describe their effectiveness on a case study.Comment: In Proceedings TAV-WEB 2010, arXiv:1009.330

State Merging with Quantifiers in Symbolic Execution

We address the problem of constraint encoding explosion which hinders the applicability of state merging in symbolic execution. Specifically, our goal is to reduce the number of disjunctions and if-then-else expressions introduced during state merging. The main idea is to dynamically partition the symbolic states into merging groups according to a similar uniform structure detected in their path constraints, which allows to efficiently encode the merged path constraint and memory using quantifiers. To address the added complexity of solving quantified constraints, we propose a specialized solving procedure that reduces the solving time in many cases. Our evaluation shows that our approach can lead to significant performance gains

Applications of Description Logic and Causality in Model Checking

Model checking is an automated technique for the verification of finite-state systems that is widely used in practice. In model checking, a model M is verified against a specification $\varphi$, exhaustively checking that the tree of all computations of M satisfies $\varphi$. When $\varphi$ fails to hold in M, the negative result is accompanied by a counterexample: a computation in M that demonstrates the failure. State of the art model checkers apply Binary Decision Diagrams(BDDs) as well as satisfiability solvers for this task. However, both methods suffer from the state explosion problem, which restricts the application of model checking to only modestly sized systems. The importance of model checking makes it worthwhile to explore alternative technologies, in the hope of broadening the applicability of the technique to a wider class of systems. Description Logic (DL) is a family of knowledge representation formalisms based on decidable fragments of first order logic. DL is used mainly for designing ontologies in information systems. In recent years several DL reasoners have been developed, demonstrating an impressive capability to cope with very large ontologies. This work consists of two parts. In the first we harness the growing ability of DL reasoners to solve model checking problems. We show how DL can serve as a natural setting for representing and solving a model checking problem, and present a variety of encodings that translate such problems into consistency queries in DL. Experimental results, using the Description Logic reasoner FaCT++, demonstrate that for some systems and properties, our method can outperform existing ones. In the second part we approach a different aspect of model checking. When a specification fails to hold in a model and a counterexample is presented to the user, the counterexample may itself be complex and difficult to understand. We propose an automatic technique to find the computation steps and their associated variable values, that are of particular importance in generating the counterexample. We use the notion of causality to formally define a set of causes for the failure of the specification on the given counterexample. We give a linear-time algorithm to detect the causes, and we demonstrate how these causes can be presented to the user as a visual explanation of the failure

Complete intersections and mod p cochains

We give homotopy invariant definitions corresponding to three well known properties of complete intersections, for the ring, the module theory and the endomorphisms of the residue field, and we investigate them for the mod p cochains on a space, showing that suitable versions of the second and third are equivalent and that the first is stronger. We are particularly interested in classifying spaces of groups, and we give a number of examples. This paper follows on from arXiv:0906.4025 which considered the classical case of a commutative ring and arXiv:0906.3247 which considered the case of rational homotopy theory.Comment: To appear in AG

The "Black Box" Behind Prison-Based Vocational Training Programs

Despite the great importance of prison vocational programs, studies have pointed to a wide variety of barriers that inhibit the released prisoner's chances to integrate into the labor market. The present qualitative investigation was designed to crack the "black box" behind six vocational programs implemented in the Israel Prison Service (IPS). Our findings based on the interviews with all the supervisors in the programs emphasized several factors that seem necessary for the success of the different vocational programs. The interviews show that training in a correctional environment poses a number of major difficulties for the respondents. Furthermore, a significant part of the prisoners' motivation to participate in the training programs is not necessarily related to the desire to find work after release. It was also found that a relatively long training, which makes it possible to find work in the field even during the period of incarceration, holistically addresses the various needs of the prisoner, and corresponds to the job market requirements, increases the chances of its participants to find employment also after their release from prison. When the characteristics of the various programs were examined, it was found that in addition to the characteristics of prisoners, one must also consider structural characteristics such: to what extent do the programs comply with the requirements of the Israeli labor market, confer a formal diploma at the end of the training period, or allow integration into the work force after release

"Judaism Intertwines with Worldly Good": A Qualitative Study on Religious Rehabilitation Programs in the Israeli Prison Service

Background: Religion with its religious institutions has played a key role in shaping punishment and rehabilitation of offenders throughout history. The aim of these programs is to transform a person spiritually and lead them to intra-personal changes on the religious level by prompting repentance or the reaffirmation of one's faith. Objectives: We present qualitative findings from an evaluation of two religious programs operating in the Israeli Prison Service: The Torah Rehabilitation Program (TRP) that functions as a religious community within prison walls, and the Torah Study Program (TSP) in which prisoners participate faith-based studies four hours a day. The main research question that led the researchers was how Judaism provides opportunities for prisoner’s rehabilitation. Method: This research is a qualitative study that includes seven interviews with seven Rabbis who work in the Israeli Prison Service and lead the religious programs. The interviewees were involved in the formulation and implementation of the religious correctional programs. Results: The interviewees have raised a link between Jewish beliefs and practices, including atonement, and the foundations of prisoners’ rehabilitation. Among the themes that have been raised: promoting moral action; giving prisoners a second chance; providing opportunities for repentance and atonement; supervision; placing emphasis on behavioral norms; focusing on belonging and commitment to a community; working alongside Torah; learning and providing a unique response to each individual according to their characteristics and needs. Conclusions: The emerging themes raised in the interviews correspond well with theoretical ideas found in the field of corrections in general and in positive criminology in particular

The configuration space of an arachnoid mechanism

ABSTRACT. The configuration spaces of arachnoid mechanisms are analyzed in this paper. These mechanisms consist of k branches each of which has an arbitrary number of links and a fixed initial point, while all branches end at one common end-point. It is shown that generically, the configuration spaces of such mechanisms are manifolds, and the conditions for the exceptional cases are determined. The configuration space of planar arachnoid mechanisms having k branches, each with two links is analyzed for both the non-singular and the singular cases

Topological and Kinematic Singularities for a Class of Parallel Mechanisms

We study singularities for a parallel mechanism with a planar moving platform in ℝ(=2,3), with joints which are universal, spherical (spatial case), or rotational (planar case). For such mechanisms, we give a necessary condition for a topological singularity to occur, and describe the corresponding kinematic singularity. An example is provided

Physical activity and pre-diabetes—an unacknowledged mid-life crisis: findings from NHANES 2003–2006

The prevalence of pre-diabetes (PD) among US adults has increased substantially over the past two decades. By current estimates, over 34% of US adults fall in the PD category, 84% of whom meet the American Diabetes Association’s criteria for impaired fasting glucose (IFG). Low physical activity (PA) and/or sedentary behavior are key drivers of hyperglycemia. We examined the relationship between PD and objectively measured PA in NHANES 2003–2006 of 20,470 individuals, including 7,501 individuals between 20 and 65 yrs.We excluded all participants without IFG measures or adequate accelerometry data (final N = 1,317). Participants were identified as PD if FPG was 100–125 mg/dL (5.6–6.9 mmol/L). Moderate and vigorous PA in minutes/day individuals were summed to create the exposure variable “moderate-vigorous PA” (MVPA). The analysis sample included 884 normoglycemic persons and 433 with PD. There were significantly fewer PD subjects in the middle (30.3%) and highest (24.6%) tertiles of PA compared to the lowest tertile (35.5%). After adjusting for BMI, participants were 0.77 times as likely to be PD if they were in the highest tertile compared to the lowest PA tertile (p < 0.001). However, these results were no longer significant when age and BMI were held constant. Univariate analysis revealed that physical activity was associated with decreased fasting glucose of 0.5 mg/dL per minute of MVPA, but multivariate analysis adjusting for age and BMI was not significant. Overall, our data suggest a negative association between measures of PA and the prevalence of PD in middle-aged US adults independent of adiposity, but with significant confounding influence from measures of BMI and age