598 research outputs found
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
CREOLE: a Universal Language for Creating, Requesting, Updating and Deleting Resources
In the context of Service-Oriented Computing, applications can be developed
following the REST (Representation State Transfer) architectural style. This
style corresponds to a resource-oriented model, where resources are manipulated
via CRUD (Create, Request, Update, Delete) interfaces. The diversity of CRUD
languages due to the absence of a standard leads to composition problems
related to adaptation, integration and coordination of services. To overcome
these problems, we propose a pivot architecture built around a universal
language to manipulate resources, called CREOLE, a CRUD Language for Resource
Edition. In this architecture, scripts written in existing CRUD languages, like
SQL, are compiled into Creole and then executed over different CRUD interfaces.
After stating the requirements for a universal language for manipulating
resources, we formally describe the language and informally motivate its
definition with respect to the requirements. We then concretely show how the
architecture solves adaptation, integration and coordination problems in the
case of photo management in Flickr and Picasa, two well-known service-oriented
applications. Finally, we propose a roadmap for future work.Comment: In Proceedings FOCLASA 2010, arXiv:1007.499
A Logical Verification Methodology for Service-Oriented Computing
We introduce a logical verification methodology for checking behavioural properties of service-oriented computing systems. Service properties are described by means of SocL, a branching-time temporal logic that we have specifically designed to express in an effective way distinctive aspects of services, such as, e.g., acceptance of a request, provision of a response, and correlation among service requests and responses. Our approach allows service properties to be expressed in such a way that
they can be independent of service domains and specifications. We show an instantiation of our general methodology that uses the formal language COWS to conveniently specify services and the expressly developed software tool CMC to assist the user in the task of verifying SocL formulae over service specifications. We demonstrate feasibility and effectiveness of our methodology by means of the specification and the analysis of a case study in the automotive domain
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
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
An Integrated Methodology for Creating Composed Web/Grid Services
This thesis presents an approach to design, specify, validate, verify, implement, and evaluate composed web/grid services. Web and grid services can be composed to create new services
with complex behaviours. The BPEL (Business Process Execution Language) standard was created to enable the orchestration of web services, but there have also been investigation of
its use for grid services. BPEL specifies the implementation of service composition but has no formal semantics; implementations are in practice checked by testing. Formal methods are
used in general to define an abstract model of system behaviour that allows simulation and reasoning about properties. The approach can detect and reduce potentially costly errors at
design time.
CRESS (Communication Representation Employing Systematic Specification) is a domainindependent,
graphical, abstract notation, and integrated toolset for developing composite web service. The original version of CRESS had automated support for formal specification in
LOTOS (Language Of Temporal Ordering Specification), executing formal validation with MUSTARD (Multiple-Use Scenario Testing and Refusal Description), and implementing in
BPEL4WS as the early version of BPEL standard. This thesis work has extended CRESS and its integrated tools to design, specify, validate, verify, implement, and evaluate composed web/grid
services. The work has extended the CRESS notation to support a wider range of service compositions, and has applied it to grid services as a new domain. The thesis presents two new
tools, CLOVE (CRESS Language-Oriented Verification Environment) and MINT (MUSTARD Interpreter), to respectively support formal verification and implementation testing. New work
has also extended CRESS to automate implementation of composed services using the more recent BPEL standard WS-BPEL 2.0
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