Comprehensive Monitor-Oriented Compensation Programming

Compensation programming is typically used in the programming of web service compositions whose correct implementation is crucial due to their handling of security-critical activities such as financial transactions. While traditional exception handling depends on the state of the system at the moment of failure, compensation programming is significantly more challenging and dynamic because it is dependent on the runtime execution flow - with the history of behaviour of the system at the moment of failure affecting how to apply compensation. To address this dynamic element, we propose the use of runtime monitors to facilitate compensation programming, with monitors enabling the modeller to be able to implicitly reason in terms of the runtime control flow, thus separating the concerns of system building and compensation modelling. Our approach is instantiated into an architecture and shown to be applicable to a case study.Comment: In Proceedings FESCA 2014, arXiv:1404.043

Specification and analysis of SOC systems using COWS: a finance case study

Service-oriented computing, an emerging paradigm for distributed computing based on the use of services, is calling for the development of tools and techniques to build safe and trustworthy systems, and to analyse their behaviour. Therefore many researchers have proposed to use process calculi, a cornerstone of current foundational research on specification and analysis of concurrent and distributed systems. We illustrate this approach by focussing on COWS, a process calculus expressly designed for specifying and combining services, while modelling their dynamic behaviour. We present the calculus and one of the analysis techniques it enables, that is based on the temporal logic SocL and the associated model checker CMC. We demonstrate applicability of our tools by means of a large case study, from the financial domain, which is first specified in COWS, and then analysed by using SocL to express many significant properties and CMC to verify them

Using formal methods to develop WS-BPEL applications

In recent years, WS-BPEL has become a de facto standard language for orchestration of Web Services. However, there are still some well-known difficulties that make programming in WS-BPEL a tricky task. In this paper, we firstly point out major loose points of the WS-BPEL specification by means of many examples, some of which are also exploited to test and compare the behaviour of three of the most known freely available WS-BPEL engines. We show that, as a matter of fact, these engines implement different semantics, which undermines portability of WS-BPEL programs over different platforms. Then we introduce Blite, a prototypical orchestration language equipped with a formal operational semantics, which is closely inspired by, but simpler than, WS-BPEL. Indeed, Blite is designed around some of WS-BPEL distinctive features like partner links, process termination, message correlation, long-running business transactions and compensation handlers. Finally, we present BliteC, a software tool supporting a rapid and easy development of WS-BPEL applications via translation of service orchestrations written in Blite into executable WS-BPEL programs. We illustrate our approach by means of a running example borrowed from the official specification of WS-BPEL

A Calculus for Orchestration of Web Services

Service-oriented computing, an emerging paradigm for distributed computing based on the use of services, is calling for the development of tools and techniques to build safe and trustworthy systems, and to analyse their behaviour. Therefore, many researchers have proposed to use process calculi, a cornerstone of current foundational research on specification and analysis of concurrent, reactive, and distributed systems. In this paper, we follow this approach and introduce CWS, a process calculus expressly designed for specifying and combining service-oriented applications, while modelling their dynamic behaviour. We show that CWS can model all the phases of the life cycle of service-oriented applications, such as publication, discovery, negotiation, orchestration, deployment, reconfiguration and execution. We illustrate the specification style that CWS supports by means of a large case study from the automotive domain and a number of more specific examples drawn from it

Reconfigurable and software-defined networks of connectors and components

The diffusion of adaptive systems motivate the study of models of software entities whose interaction capabilities can evolve dynamically. In this paper we overview the contributions in the ASCENS project in the area of software defined networks and of reconfigurable connectors. In particular we highlight: (i) the definition of the Network-conscious pi-calculus and its use in the modeling and verification of the PASTRY protocol, and (ii) the mutual correspondence between different frameworks for defining networks of connectors together with two suitable enhancements for addressing dynamically changing systems

Recovery within long running transactions

As computer systems continue to grow in complexity, the possibilities of failure increase. At the same time, the increase in computer system pervasiveness in day-to-day activities brought along increased expectations on their reliability. This has led to the need for effective and automatic error recovery techniques to resolve failures. Transactions enable the handling of failure propagation over concurrent systems due to dependencies, restoring the system to the point before the failure occurred. However, in various settings, especially when interacting with the real world, reversal is not possible. The notion of compensations has been long advocated as a way of addressing this issue, through the specification of activities which can be executed to undo partial transactions. Still, there is no accepted standard theory; the literature offers a plethora of distinct formalisms and approaches. In this survey, we review the compensations from a theoretical point of view by: (i) giving a historic account of the evolution of compensating transactions; (ii) delineating and describing a number of design options involved; (iii) presenting a number of formalisms found in the literature, exposing similarities and differences; (iv) comparing formal notions of compensation correctness; (v) giving insights regarding the application of compensations in practice; and (vi) discussing current and future research trends in the area.peer-reviewe

Automatic dynamic generation of likely invariants for WS-BPEL compositions

The wide adoption of Web Services has led to the development of languages to compose them, like the WS-BPEL standard. In order to check whether the composition works as expected, one common approach is to analyze it and infer functional properties describing its behavior. Traditional approaches for inferring properties in WS-BPEL have been static: compositions are transformed into specialized analysis models based on some formalization. However, this formalization could be inexact due to theoretical limitations or differing interpretations of the standard by implementers. Dynamic invariant generation solves these problems by extracting the properties from actual executions and has been successfully used in popular languages, but not to WS-BPEL yet. In this work, we apply dynamic invariant generation to WS-BPEL, providing innovative solutions for several features that require special consideration, like highly multidimensional values in variables, an advanced type system or unstructured code. We have implemented these solutions in Takuan and evaluated its performance with several compositions of varying complexity. We present the results obtained and a comparative analysis of the efficiency and effectiveness of our solutions. Results show that the solutions are successful in reducing the cost of applying dynamic invariant generation and the number of uninteresting invariants generated

A compensating transaction example in twelve notations

The scenario of business computer systems changed with the advent of cross-entity computer interactions: computer systems no longer had the limited role of storing and processing data, but became themselves the players which actuated real-life actions. These advancements rendered the traditional transaction mechanism insufficient to deal with these new complexities of longer multi-party transactions. The concept of compensations has long been suggested as a solution, providing the possibility of executing “counter”-actions which semantically undo previously completed actions in case a transaction fails. There are numerous design options related to compensations particularly when deciding the strategy of ordering compensating actions. Along the years, various models which include compensations have emerged, each tackling in its own way these options. In this work, we review a number of notations which handle compensations by going through their syntax and semantics — highlighting the distinguishing features — and encoding a typical compensating transaction example in terms of each of these notations.peer-reviewe

Дослідження методів автоматизації проектування складних об'єктів і систем

Метою даної роботи є зменшення загальної тривалості проектувальних робіт за рахунок побудови моделей та інформаційних технологій для організацій у вигляді набору засобів автоматизації проектувальних робіт. Для досягнення мети необхідно розв`язати наступні завдання: – аналізувати інформаційні технології, використовувані при проектуванні об'єктів і дослідити процес проектування; – розробити інформаційну модель структури об'єкта дизайну; – розробити інформаційну модель процесу проектування; – розробити інформаційну технологію і порядок взаємодії її підсистем на основі створених інформаційних моделей і існуючих методів; Об'єктом дослідження є процес проектування об’єктів у спеціальності машинобудування. Предмет дослідження – модель та інформаційна технологія для розв`язання задач для автоматизації проектувальних робіт. Методи дослідження. Методологічною та теоретичною основою дослідження є наукові роботи та дослідження провідних авторів. Було використано наступні методи: методи теорії множин та орієнтованих графів, системного аналізу та побудови баз даних. Загальний обсяг роботи: 121 сторінка, 51 зображень, 13 таблиць, 67 посилань.The purpose of this work is to reduce the total duration of design work by building models and information technology for organizations in the form of a set of tools for automation of design work. To achieve this goal it is necessary to solve the following tasks: - analyze the information technology used in the design of facilities and explore the design process; - to develop an information model of the structure of the design object; - to develop an information model of the design process; - to develop information technology and the order of interaction of its subsystems on the basis of the created information models and existing methods; The object of research is the process of designing objects in the specialty of mechanical engineering. The subject of research is a model and information technology for solving problems for automation of design works. Research methods. The methodological and theoretical basis of the research are scientific works and researches of leading authors. The following methods were used: methods of set theory and oriented graphs, systems analysis and database construction. Includes: 121 pages, 51 images, 13 tables, 67 links