GCSR: A Graphical Language With Algebraic Semantics for the Specification of Real-Time Systems

Graphical Communicating Shared Resources, GCSR, is a formal language for specifying real-time systems including their functional and resource requirements. A GCSR specification consists of a set of nodes that are connected with directed, labeled edges, which describe possible execution flows. Nodes represent instantaneous selection among execution flows, or time and resource consuming system activities. In addition, a node can represent a system subcomponent, which allows modular, hierarchical, thus scalable system specifications. Edges are labeled with instantaneous communication actions or time to describe the duration of activities in the source node. GCSR supports the explicit representation of resources and priorities to resolve resource contention. The semantics of GCSR is the Algebra of Communicating Shared Resources, a timed process algebra with operational semantics that makes GCSR specifications executable. Furthermore, the process algebra provides behavioral equivalence relations between GCSR specifications. These equivalence relations can be used to replace a GCSR specification with an equivalent specification inside another, and to minimize a GCSR specification in terms of the number of nodes and edges. The paper defines the GCSR language, describes GCSR specification reductions that preserve the specification behaviors, and illustrates GCSR with example design specifications

Anti-Pattern Specification and Correction Recommendations for Semantic Cloud Services

Given the economic and technological advantages \ they offer, cloud services are increasing being offered by \ several cloud providers. However, the lack of standardized \ descriptions of cloud services hinders their discovery. \ In an effort to standardize cloud service descriptions, \ several works propose to use ontologies. Nevertheless, \ the adoption of any of the proposed ontologies \ calls for an evaluation to show its efficiency in cloud \ service discovery. Indeed, the existing cloud providers \ describe, their similar offered services in different ways. \ Thus, various existing works aim at standardizing the \ representation of cloud computing services by proposing \ ontologies. However, since the existing proposals \ were not evaluated, they might be less adopted and considered. \ Indeed, the ontology evaluation has a direct impact \ on its understandability and reusability. In this paper, \ we propose an evaluation approach to validate our \ proposed Cloud Service Ontology (CSO), to guarantee \ an adequate cloud service discovery. To this end, this \ paper has a three-fold contribution. First, we specify a \ set of patterns and anti-patterns in order to evaluate our \ CSO. Second, we define an anti-pattern detection algorithm \ based on SPARQL queries which provides a set of \ correction recommendations to help ontologists revise \ their ontology. Finally, tests were conducted in relation \ to: (i) the algorithm efficiency and (ii) anti-pattern detection \ of design anomalies as well as taxonomic and \ domain errors within CSO

Profil clinico-biologique et histopathologique des atteintes rénales du purpura rhumatoïde au Centre Hospitalier Universitaire de Tunis: The clinicopathologic characteristics of Henoch Schönlein nephritis in Tunis University Hospital

Context and objective. Hench Schönlein purpura (HSP) is a leukocytoclastic vasculitis with IgA deposits characterized by the association of cutaneous, articular and digestive involvements. Renal involvement worsens the pronostic of the disease. In Tunisia, kidney damage in HSP has not often been studied. The main objective of this work was to describe the epidemiological, clinical, biological and histological characteristics as well as to analyze the therapeutic modalities of renal involvement during IgA vasculitis in Tunisian population. Methods. Patients with HSP with nephritis from 1975 to 2017 were retrospectively studied. Results. 34 medical records of patients were compiled. Mean age at nephritis onset was 39 ± 17.6 years. Cutaneous purpura was present in 97 % of cases, gastrointestinal involvement in 68% of cases and joint involvement in 85 % of cases. Renal features were microscopic hematuria in 100% of cases, hypertension in 47% of cases, proteinuria in 85% of cases. Renal failure and nephrotic syndrome were encountered in 44 % and 41 % of cases, respectively. Average of proteinuria was 3.07 ± 2.83 g / 24 hours. Complete remission was achieved in 33% of patients and 43% of patients reached end stage renal disease requiring dialysis. Death was noted in 5 cases (17%). Conclusion. Renal involvement in adult HSP is marked by varied clinical features, mainly renal failure and progression to hemodialysis in almost 50% of cases. Contexte et objectifs. Le purpura rhumatoïde (PR) est une atteinte systémique touchant les vaisseaux de petit calibre. L’atteinte rénale fait la gravité de la maladie assombrissant le pronostic. En Tunisie, l’atteinte rénale au cours du PR est peu documentée. La présente étude avait pour objectif de décrire les caractéristiques épidémiologiques, cliniques, biologiques, histologiques et thérapeutiques de l’atteinte rénale au cours du PR propres à la population tunisienne. Méthodes. Il s’agissait d’une étude documentaire réalisée dans le plus grand centre hospitalier universitaire de Néphrologie de Tunis de 1975 à 2017. Tous les patients avaient un PR avec une atteinte rénale. Résultats. Nous avons colligé 34 patients. L’âge moyen était de 39 ± 17,6 ans avec une prédominance masculine. Le purpura cutané était présent dans 97% des cas. L’atteinte gastro-intestinale et articulaire était respectivement dans 68% des cas et dans 85% des cas. L’hématurie microscopique était présente chez tous nos patients, la protéinurie et l’hypertension artérielle ont été retrouvées dans respectivement 85% et 47% des cas. Une insuffisance rénale a été retrouvée dans 44% des cas. Le syndrome néphrotique était présent chez 41% des patients avec une protéinurie moyenne de 3.07 ± 2.83 g daily. La rémission complète a été atteinte par 33% des patients et 43% ont atteint le stade d’hémodialyse. Le décès a été rapporté dans 5 cas (17%). Conclusion. L’atteinte rénale au cours du Purpura Rhumatoïde de l’adulte est caractérisée par un tableau clinique bruyant, une insuffisance rénale fréquente et une évolution vers le stade d’hémodialyse dans presque 50% des cas

Profil étiologique des microangiopathies thrombotiques rénales au Centre Hospitalier et Universitaire de Tunis: Etiological profile of renal thrombotic microangiopathy in Tunis University Hospital

Context and objective. Renal thrombotic microangiopathy (TMA) is a histological lesion that can be observed in several pathological settings. The present study aimed to describe the different etiological contexts in which TMA has been observed and provide particularities. Methods. A retrospective and descriptive study over a 16-year period, from January 2000 to January 2016 was conducted at the Tunis University Hospital. All patients aged over 16 years and presenting with TMA at renal biopsy were analyzed. Results. 100 cases of renal TMA were collected. The mean age of patients at the time of renal biopsy was 38.5 ± 12.9 years. The clinical picture was dominated by hypertension observed in 70 patients. Results of the laboratory investigations were as follows: kidney injury was noted in 92 patients and biological TMA was observed in 10 patients. At the renal biopsy, arteriolar TMA was seen in all patients and glomerular TMA was seen in 15 patients. Seventy-three patients reached end stage renal disease. TMA was observed mainly in association with glomerular nephropathy outside lupus nephropathy in 47 cases, lupus nephropathy in 19 cases, malignant hypertension in 18 cases and post-renal transplantation in 9 cases. TMA was related to atypical hemolytic uremic syndrome in one case and 6 sporadic cases were observed. Conclusion. Renal TMA has been observed in several pathological situations. Comparative studies with matched control cases in each group but without TMA lesions should be performed to identify risk factors for developing TMA and the influence of TMA on renal prognosis in each etiological setting. Contexte et objectif. La microangiopathie thrombotique (MAT) rénale est une lésion histologique caractérisée par la présence de microthrombi obstruant les vaisseaux de la microcirculation rénale. Actuellement, les patients atteints de MAT rénale sont répartis en fonction du contexte étiologique. L’objectif de la présente étude était de décrire les différents contextes pathologiques au cours desquels une MAT rénale a été observée. Méthodes. Il s’agissait d’une étude documentaire (16 ans). L’étude a inclus tous les patients adultes ayant des lésions de MAT à la ponction biopsie rénale (PBR). Résultats. Parmi 3240 PBR réalisées, la MAT a été observée chez 100 patients soit une incidence moyenne de 6,7 cas/an. L’âge moyen était de 38,5+/-12,9 ans avec une prédominance masculine. Les lésions de MAT rénale ont été associées à plusieurs contextes pathologiques : les néphropathies glomérulaires (47%), les néphropathies lupiques (19%), l’HTA maligne (18%), post transplantation rénale (9%), postgreffe de cellules souches hématopoïétiques (1%), post partum (2%), un contexte néoplasique (1%), une origine médicamenteuse (1%), un syndrome des antiphospholipides primaire (1%), et un syndrome hémolytique et urémique (1%). Conclusion. La MAT rénale est fréquemment secondaire et s’associe à plusieurs contextes pathologiques. Cependant un SHUa/PTT sous-jacents devrait toujours être recherchés

GRAPHICAL COMMUNICATING SHARED RESOURCES: A LANGUAGE FOR THE SPECIFICATION, REFINEMENT AND ANALYSIS OF REAL-TIME SYSTEMS

The Communicating Shared Resources (CSR) paradigm is an ongoing project at the University of Pennsylvania to build a framework for the development of real-time systems. This project has been motivated by a demand for a rigorous framework in which various design alternatives for a real-time system can be formally specified and rigorously analyzed and tested before implementation. This is an effort to reduce the potentially high cost associated with incorrect operation of real-time systems which are often embedded in safety-critical applications. The work presented in this thesis is a first step towards incorporating software engineering practices into the CSR paradigm. This is achieved, on one hand, by developing a formal, graphical CSR formalism, the Graphical Communicating Shared Resources (GCSR); the GCSR language adopts the intuitive concepts of nodes and edges in state diagrams, an informal specification language that is popular within the software engineering community. In addition, defining a refinement theory for GCSR allows the development of real-time systems within this formalism in a top-down and modular fashion, also a popular design methodology within the software engineering community. The GCSR language adopts a syntax that allows a modular and hierarchical, thus, scalable description of a real-time system. It supports notions of comunication through events, interrupt, concurrency, and time to describe the functional and temporal requirements of a real-time system. In addition, GCSR allows the explicit representation of resources and priorities to resolve resource contention, in such a way that produces easy to understand and modify specifications. The semantics of GCSR is defined operationally either through a direct translation of a GCSR description to a labeled transition system, or indirectly through a sound translation to the Algebra of Communicating Shared Resources (ACSR) [LBGG94] a timed process algebra that also has an operational semantics. The GCSR-ACSR correspondence makes GCSR benefit from process algebraic analysis techniques such as equivalence checking, state space exploration, testing as well as simulation. In addition, the tight correspondence between GCSR and ACSR makes it possible to use the graphical and textual notations interchangeably and to have a sound theory for graphical transformation operations, e.g., to minimize the number of edges and nodes in a GCSR specification without affecting the behavioral description. To support the top-down and modular development of a real-time specification in GCSR, we have augmented ACSR and thus GCSR with a refinement theory. The refinement theory allows relabeling of events, addition of implementation events, and substitution of a time and resource-consuming action with a process that may use fewer or more resources than the refined action. Consistency between an abstract specification and a refined specification is defined in terms of an ordering relation over traces that is extended to sets of traces according to the Hoare ordering or Egli-Milner ordering. The trace ordering relation relates traces that share timing properties such as equal duration and preservation of timed occurrences of communication events of the abstract specification. To facilitate the practical use of the refinement theory, we have characterized the extended trace ordering relations by a set of transformation rules that syntactically derive a refined process from an abstract one. The transformation rules define basic graphical operations that represent GCSR refinements. To experiment with the GCSR language and its refinement theory, we have developed a tool set that allows the specification, refinement, and analysis of real-time systems modeled in GCSR. We report our evaluation in the case of the Production Cell case study [LL95]

Expressing and Analyzing Timing Constraints in Message Sequence Chart Specifications

Message Sequence Charts (MSCs) are increasingly supported in software engineering tools and methodologies for communication systems. The last Z.120 standard extends MSCs with operators to organize them in a compositional, hierarchical fashion to describe systems with non-trivial sizes. When dealing with timing constraints, the standard is still evolving along with several proposals. This paper first reviews proposed extensions of MSCs to describe timing constraints. Secondly, the paper describes an analysis technique for timing consistency in iterating and branching MSC specifications. The analysis extends efficient current techniques for timing analysis of MSCs with no loops or branchings. Finally, we use an example to illustrate our analysis technique. ii Contents 1 Introduction 1 2 Timing Constraints in Basic MSCs 2 2.1 Syntax . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 2.2 Timing Analysis Based on Timers and Delay Intervals ...

Specification and Analysis of Real-Time Systems with PARAGON

This paper describes a methodology for the specification and analysis of distributed real-time systems using the toolset called PARAGON. PARAGON is based on the Communicating Shared Resources paradigm, which allows a real-time system to be modeled as a set of communicating processes that compete for shared resources. PARAGON supports both visual and textual languages for describing real-time systems. It offers automatic analysis based on state space exploration as well as user-directed simulation. Our experience with using PARAGON in several case studies resulted in a methodology that includes design patterns and abstraction heuristics, as well as an overall process. This paper briefly overviews the communicating shared resource paradigm and its toolset PARAGON, including the textual and visual specification languages. The paper then describes our methodology with special emphasis on heuristics that can be used in PARAGON to reduce the state space. To illustrate the methodology, we use..