1,024 research outputs found
Issues about the Adoption of Formal Methods for Dependable Composition of Web Services
Web Services provide interoperable mechanisms for describing, locating and
invoking services over the Internet; composition further enables to build
complex services out of simpler ones for complex B2B applications. While
current studies on these topics are mostly focused - from the technical
viewpoint - on standards and protocols, this paper investigates the adoption of
formal methods, especially for composition. We logically classify and analyze
three different (but interconnected) kinds of important issues towards this
goal, namely foundations, verification and extensions. The aim of this work is
to individuate the proper questions on the adoption of formal methods for
dependable composition of Web Services, not necessarily to find the optimal
answers. Nevertheless, we still try to propose some tentative answers based on
our proposal for a composition calculus, which we hope can animate a proper
discussion
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
Service discovery and negotiation with COWS
To provide formal foundations to current (web) services technologies, we put forward using COWS, a process calculus for specifying, combining and analysing services, as a uniform formalism for modelling all the relevant phases of the life cycle of service-oriented applications, such as publication, discovery, negotiation, deployment and execution. In this paper, we show that constraints and operations on them can be smoothly incorporated in COWS, and propose a disciplined way to model multisets of constraints and to manipulate them through appropriate interaction protocols. Therefore, we demonstrate that also QoS requirement specifications and SLA achievements, and the phases of dynamic service discovery and negotiation can be comfortably modelled in COWS. We illustrate our approach through a scenario for a service-based web hosting provider
SCC: A Service Centered Calculus
We seek for a small set of primitives that might serve as a basis for formalising and programming service oriented applications over global computers. As an outcome of this study we introduce here SCC, a process calculus that features explicit notions of service definition, service invocation and session handling. Our proposal has been influenced by Orc, a programming model for structured orchestration of services, but the SCC’s session handling mechanism allows for the definition of structured interaction protocols, more complex than the basic request-response provided by Orc. We present syntax and operational semantics of SCC and a number of simple but nontrivial programming examples that demonstrate flexibility of the chosen set of primitives. A few encodings are also provided to relate our proposal with existing ones
CaSPiS: A Calculus of Sessions, Pipelines and Services
Service-oriented computing is calling for novel computational models and languages with well
disciplined primitives for client-server interaction, structured orchestration and unexpected events handling. We present CaSPiS, a process calculus where the conceptual abstractions of sessioning and pipelining play a central role for modelling service-oriented systems. CaSPiS sessions are two-sided, uniquely named and can be nested. CaSPiS pipelines permit orchestrating the flow of data produced by different sessions. The calculus is also equipped with operators for handling (unexpected) termination of the partner’s side of a session. Several examples are presented to provide evidence of the flexibility of the chosen set of primitives. One key contribution is a fully abstract encoding of Misra et al.’s orchestration language Orc. Another main result shows that in CaSPiS it is possible to program a “graceful termination” of nested sessions, which guarantees that no session is forced to hang forever after the loss of its partner
A Rigorous Methodology for Composing Services
Creating new services through composition of existing ones is an attractive option. However, composition can be complex and service compatibility needs to be checked. A rigorous and industrially-usable methodology is therefore desirable required for creating, verifying, implementing and validating composed services. An explanation is given of the approach taken by CRESS (Communication Representation Employing Systematic Specification). Formal verification and validation are performed through automated translation to LOTOS (Language Of Temporal Ordering Specification). Implementation and validation are performed through automated translation to BPEL (Business Process Execution Logic) and WSDL (Web Services Description Language). The approach is illustrated with an application to grid service composition in e-Social Science
cJoin: join with communicating transactions
This paper proposes a formal approach to the design and programming of Long Running Transactions (LRT). We exploit techniques from process calculi to define cJoin, which is an extension of the join calculus with few well-disciplined primitives for LRT. Transactions in cJoin are intended to describe the transactional interaction of several partners, under the assumption that any partner executing a transaction may communicate only with other transactional partners. In such case, the transactions run by any party are bound to achieve the same outcome (i.e., all succeed or all fail). Hence, a distinguishing feature of cJoin, called dynamic joinability, is that ongoing transactions can be merged to complete their tasks and when this happens either all succeed or all abort. Additionally, cJoin is based on compensations, i.e., partial executions of transactions are recovered by executing user-defined programs instead of providing automatic roll-back. The expressiveness and generality of cJoin is demonstrated by many examples addressing common programming patterns. The mathematical foundation is accompanied by a prototype language implementation, which is an extension of the jocaml compiler
Automata for specifying and orchestrating service contracts
An approach to the formal description of service contracts is presented in
terms of automata. We focus on the basic property of guaranteeing that in the
multi-party composition of principals each of them gets his requests satisfied,
so that the overall composition reaches its goal. Depending on whether requests
are satisfied synchronously or asynchronously, we construct an orchestrator
that at static time either yields composed services enjoying the required
properties or detects the principals responsible for possible violations. To do
that in the asynchronous case we resort to Linear Programming techniques. We
also relate our automata with two logically based methods for specifying
contracts
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