Modeling a distributed Heterogeneous Communication System using Parametric Timed Automata

In this report, we study the application of the Parametric Timed Automata(PTA) tool to a concrete case of a distributed Heterogeneous Communication System (HCS). The description and requirements of HCS are presented and the system modeling is explained carefully. The system models are developed in UPPAAL and validated by different test cases. Part of the system models are then converted into parametric timed automata and the schedulability checking is run to produce the schedulability regions

Risk Factors of Streptococcus suis Infection in Vietnam. A Case-Control Study

Background: Streptococcus suis infection, an emerging zoonosis, is an increasing public health problem across South East Asia and the most common cause of acute bacterial meningitis in adults in Vietnam. Little is known of the risk factors underlying the disease. Methods and Findings: A case-control study with appropriate hospital and matched community controls for each patient was conducted between May 2006 and June 2009. Potential risk factors were assessed using a standardized questionnaire and investigation of throat and rectal S. suis carriage in cases, controls and their pigs, using real-time PCR and culture of swab samples. We recruited 101 cases of S. suis meningitis, 303 hospital controls and 300 community controls. By multivariate analysis, risk factors identified for S. suis infection as compared to either control group included eating "high risk" dishes, including such dishes as undercooked pig blood and pig intestine (OR1 = 2.22; 95% CI = [1.15-4.28] and OR2 = 4.44; 95% CI = [2.15-9.15]), occupations related to pigs (OR1 = 3.84; 95% CI = [1.32-11.11] and OR2 = 5.52; 95% CI = [1.49-20.39]), and exposures to pigs or pork in the presence of skin injuries (OR1 = 7.48; 95% CI = [1.97-28.44] and OR2 = 15.96; 95% CI = [2.97-85.72]). S. suis specific DNA was detected in rectal and throat swabs of 6 patients and was cultured from 2 rectal samples, but was not detected in such samples of 1522 healthy individuals or patients without S. suis infection. Conclusions: This case control study, the largest prospective epidemiological assessment of this disease, has identified the most important risk factors associated with S. suis bacterial meningitis to be eating 'high risk' dishes popular in parts of Asia, occupational exposure to pigs and pig products, and preparation of pork in the presence of skin lesions. These risk factors can be addressed in public health campaigns aimed at preventing S. suis infectio

A Clinical and Epidemiological Investigation of the First Reported Human Infection With the Zoonotic Parasite Trypanosoma evansi in Southeast Asia.

BACKGROUND: Trypanosomais a genus of unicellular parasitic flagellate protozoa.Trypanosoma bruceispecies and Trypanosoma cruziare the major agents of human trypanosomiasis; other Trypanosomaspecies can cause human disease, but are rare. In March 2015, a 38-year-old woman presented to a healthcare facility in southern Vietnam with fever, headache, and arthralgia. Microscopic examination of blood revealed infection with Trypanosoma METHODS: Microscopic observation, polymerase chain reaction (PCR) amplification of blood samples, and serological testing were performed to identify the infecting species. The patient's blood was screened for the trypanocidal protein apolipoprotein L1 (APOL1), and a field investigation was performed to identify the zoonotic source. RESULTS: PCR amplification and serological testing identified the infecting species as Trypanosoma evansi.Despite relapsing 6 weeks after completing amphotericin B therapy, the patient made a complete recovery after 5 weeks of suramin. The patient was found to have 2 wild-type APOL1 alleles and a normal serum APOL1 concentration. After responsive animal sampling in the presumed location of exposure, cattle and/or buffalo were determined to be the most likely source of the infection, with 14 of 30 (47%) animal blood samples testing PCR positive forT. evansi. CONCLUSIONS: We report the first laboratory-confirmed case ofT. evansiin a previously healthy individual without APOL1 deficiency, potentially contracted via a wound while butchering raw beef, and successfully treated with suramin. A linked epidemiological investigation revealed widespread and previously unidentified burden ofT. evansiin local cattle, highlighting the need for surveillance of this infection in animals and the possibility of further human cases

A Novel Technique for Computing Craig Interpolants in Satisfiabilility Modulo the Theory of Integer Linear Arithmetic

In this thesis we present a solution to the interpolation problem of LA(Z) based on interpolant generation for conjunctions of LA(Z) equalities and weak inequalities. Although our approach was inspired by Brillout et al.’s interpolating sequent calculus, it differs from the latter in that our interpolation method is based on cutting-plane proofs of unsatisfiability rather than sequent-calculus proofs and consists of interpolation rules built to reflect the cutting plane rules. The proposed algorithm has been implemented within MATHSAT SMT solver and tested for simple cases

A Tag Contract Framework for Modeling Heterogeneous Systems

In the distributed development of modern IT systems, contracts play a vital role in ensuring interoperability of components and adherence to specifica- tions. The design of embedded systems, however, is made more complex by the heterogeneous nature of components, which are often described using different models and interaction mechanisms. Composing such components is generally not well-defined, making design and verification difficult. Sev- eral denotational frameworks have been proposed to handle heterogeneity using a variety of approaches. However, the application of heterogeneous modeling frameworks to contract-based design has not yet been investigated. In this work, we develop an operational model with precise heterogeneous denotational semantics, based on tag machines, that can represent hetero- geneous composition, and provide conditions under which composition can be captured soundly and completely. The operational framework is imple- mented in a prototype tool which we use for experimental evaluation. We then construct a full contract model and introduce heterogeneous compo- sition, refinement, dominance, and compatibility between contracts, alto- gether enabling a formalized and rigorous design process for heterogeneous systems. Besides, we also develop a generic algebraic method to synthe- size or refine a set of contracts so that their composition satisfies a given contract

An Operational Contract Framework for Heterogeneous Systems

Modern IT systems are increasingly being built by assembling components that are pre-designed or developed concurrently in a distributed manner. In this context, contracts play a vital role for ensuring interoperability of components and adherence to specifications. For the design of e.g. embedded systems, additional complexity is found in heterogeneity of components: such systems are composed of components of very different nature, e.g. mechanical or electronic. Heterogeneity adds extra complexity to systems design, as composition of heterogeneous components is generally not well-defined, hence making design and verification difficult. So far, few approaches have attempted to address heterogeneity for embedded systems, and yet none of them has demonstrated to be really effective. Meanwhile, denotational mathematical frameworks for reasoning effectively on heterogeneous composition have recently been made available in the literature, but their operational application to a contract-based design flow is still missing. In this work, we propose a heterogeneous contract theory for embedded systems build on the tag machine formalism. We introduce heterogeneous composition, refinement, dominance, and compatibility of contracts, altogether enabling a formalized and rigorous design process for heterogeneous embedded systems

Efficient Interpolant Generation in Satisfiability Modulo Linear Integer Arithmetic

The problem of computing Craig interpolants in SAT and SMT has recently received a lot of interest, mainly for its applications in formal verification. Efficient algorithms for interpolant generation have been presented for some theories of interest ---including that of equality and uninterpreted functions, linear arithmetic over the rationals, and their combination--- and they are successfully used within model checking tools. For the theory of linear arithmetic over the integers (LA(Z)), however, the problem of finding an interpolant is more challenging, and the task of developing efficient interpolant generators for the full theory LA(Z) is still the objective of ongoing research. In this paper we try to close this gap. We build on previous work and present a novel interpolation algorithm for SMT(LA(Z)), which exploits the full power of current state-of-the-art SMT(LA(Z)) solvers. We demonstrate the potential of our approach with an extensive experimental evaluation of our implementation of the proposed algorithm in the MathSAT SMT solver

A Tag Contract Framework for Modeling Heterogeneous Systems

International audienceDevelopment of distributed systems can be supported effectively by a contract-based methodology as contracts can ensure interoperability of components and adherence to specifications. Such development can become very complex since distributed systems can consist of components which are heterogeneous in terms of computational and interactive model. Several frameworks, both operational and denotational, have been proposed to handle heterogeneity using a variety of approaches. However, the application of those frameworks to contract-based design has not yet been investigated. In this work, we adopt the operational mechanism of tag machines to represent heterogeneous systems and construct a full contract model. We introduce heterogeneous composition, refinement, dominance and compatibility between contracts, altogether enabling a formalized and rigorous design process for heterogeneous systems. Besides, we also develop a method to synthesize or refine the component models so that their composition satisfies a given contract