Realizability Of Choreographies Research Articles

Generating Event Structure from Set of Acyclic Relations in Choreography Realization

Generating Event Structure from Set of Acyclic Relations in Choreography Realization

Synthesis of context‐aware business‐to‐business processes for location‐based services through choreographies

AbstractModern technologies and emerging wireless communication solutions in the Information and Communications Technology (ICT) world are empowering the spread of the most disparate ready‐to‐use software services distributed over the globe and accessed by an increasing number of users. This state of affairs encourages the development of systems based on the reuse of existing services through composition approaches, notably choreographies. Also Public Administrations are driven towards a digitalization process which exploits composition approaches to build complex and interoperable systems that can be remotely accessed by citizens and authorities. However, an automatic support is needed in order to realize the service composition and the distributed coordination logic that enforces the correct choreography realization. Moreover, the need for building dynamic and user‐centered systems calls for the realization of choreographies capable to adjust their behavior to the surrounding context. This work presents our proposal for addressing the choreography realization problem, by describing an automated process for the synthesis of choreography‐based systems. The synthesized systems are location‐aware and able to adapt the services' interaction according to the user's needs and context conditions. We show and evaluate our approach at work on a real use case scenario in the Public Administration domain.

Realizable causal-consistent reversible choreographies for systems with first-in-first-out communication channels

We re-engineer a pomset-based abstract semantics (and the associated semantic constraints) recently proposed for compositionally specified choreographies for systems of components communicating over first-in-first-out channels. We prove that the original semantics over-specifies components' behaviour and that for this (but not only this) reason, the original semantic constraints are insufficient for the realizability of choreographies. We remove the problematic over-specification in the semantics, extend the semantics to explicitly specified interaction pomset sets, define an abstract syntax of choreographies and rephrase choreography semantics in terms of it, and newly provide a syntax-independent definition of choreography well-formedness. We prove that choreographies well-formed in the new sense are realizable and under a certain additional condition also causal-consistent reversible. Devising a set of rules for inferring well-formedness of choreographies compositionally, we correct the semantic constraints originally claimed sufficient for operands of individual composition operators. Our constraints and our definition of choreography well-formedness are in certain ways also less restrictive than the original ones. In particular, we newly allow also choreographies exploiting accidental event orderings.

Formal design of scalable conversation protocols using Event‐B: Validation, experiments, and benchmarks

AbstractContemporary interaction‐based complex systems are often built by reusing existing distributed peers, which have to coordinate with each other to fulfill the client, system, and environment requirements. In this paper, we address the design of distributed systems composed of peers (state‐transitions systems) communicating through message exchanges. We consider choreographies as the formal model, allowing a developer to describe and specify peers coordination as a set of conversations; ie, all sequences of messages exchanged between the communicating peers. Proceeding this way requires building neither the individual peers nor their composition as they may be obtained by the choreography projection. The correctness of the preservation of such messages exchanges by each peer obtained after projection is a key issue, known as the realizability problem. Checking choreography realizability is mandatory to build third‐party applications with no coordination error, eg, absence of deadlocks, missing messages, and erroneous messaging order. In our previous work, we have proposed a set of composition operators, allowing designers to build realizable choreographies that are represented by conversation protocols (CPs). In this work, realizability is guaranteed by construction. We rely on the correct‐by‐construction Event‐B method to prove that each CP constructed using our operators is realizable. In this paper, we show how our approach applies and scales to a set of use cases borrowed from the literature and used by the research community. We also show that our approach allows to detect failures and failure recovery in case realizability does not hold.

Choreography Realizability Enforcement through the Automatic Synthesis of Distributed Coordination Delegates

In the near future we will be surrounded by a virtually infinite number of software applications that provide services in the digital space. This situation promotes reuse-based software production through composition of existing software services distributed over the Internet. Choreographies are a form of decentralized composition that model the external interaction of the participant services by specifying peer-to-peer message exchanges from a global perspective. When third-party (possibly black-box) services are to be composed, obtaining the distributed coordination logic required to enforce the realizability of the specified choreography is a non-trivial and error prone task. Automatic support is then needed. In this paper, we propose a formal approach to the enforcement of choreography realizability through the automatic synthesis of distributed Coordination Delegates (CDs). CDs are additional software entities with respect to the choreography participants. They are synthesized in order to proxify and control the participant services interaction. When interposed among the services, the synthesized entities enforce the collaboration prescribed by the choreography specification. We state correctness of our synthesis method and illustrate its formalization at work on an explanatory example. • A method for the automatic realizability enforcement of service choreographies. • The method accounts for services communicating synchronously and/or asynchronously. • Coordination Delegates are synthesized to mediate the services' interaction. • The method is rigorously assessed and the proof of its correctness is also given. • The method underlies the R&D work of the EU H2020 CHOReVOLUTION project.

Choreography Realization by Re-Constructible Decomposition of Acyclic Relations

Choreography Realization by Re-Constructible Decomposition of Acyclic Relations

Deciding choreography realizability

Since software systems are becoming increasingly more concurrent and distributed, modeling and analysis of interactions among their components is a crucial problem. In several application domains, message-based communication is used as the interaction mechanism, and the communication contract among the components of the system is specified semantically as a state machine. In the service-oriented computing domain such communication contracts are called "choreography" specifications. A choreography specification identifies allowable ordering of message exchanges in a distributed system. A fundamental question about a choreography specification is determining its realizability, i.e., given a choreography specification, is it possible to build a distributed system that communicates exactly as the choreography specifies? Checking realizability of choreography specifications has been an open problem for several years and it was not known if this was a decidable problem. In this paper we give necessary and sufficient conditions for realizability of choreographies. We implemented the proposed realizability check and our experiments show that it can efficiently determine the realizability of 1) web service choreographies, 2) Singularity OS channel contracts, and 3) UML collaboration (communication) diagrams.

Realizability of Choreographies Using Process Algebra Encodings

Service-oriented computing has emerged as a new software development paradigm that enables implementation of Web accessible software systems that are composed of distributed services which interact with each other via exchanging messages. Modeling and analysis of interactions among services is a crucial problem in this domain. Interactions among a set of services that participate in a service composition can be described from a global point of view as a choreography. Choreographies can be specified using specification languages such as Web Services Choreography Description Language (WS-CDL) and visualized using graphical formalisms such as collaboration diagrams. In this paper, we present an encoding of collaboration diagrams into the LOTOS process algebra for choreography analysis. This encoding allows us to (1) check the temporal properties of choreographies using a LOTOS verification tool set called the Construction and Analysis of Distributed Processes (CADP) toolbox, (2) check the realizability of choreographies for both synchronous communication and bounded asynchronous communication, and (3) automate the peer generation process. Realizability indicates whether peers can be generated from a given choreography specification in such a way that the interactions of the generated peers exactly match the choreography specification. If a collaboration diagram is unrealizable, our approach extends the peer generation process by adding extra communication that guarantees that the peers behave according to the choreography specification.

Synthesis of state machine diagrams from communication diagrams using Petri nets

Service-oriented architecture is an architecture style to build up a large-scale networked system composed of a set of components or functions, each of which is called a service. A problem to construct behavioral models of services from given global interaction specifications, called choreography, is known as the choreography realization problem. The constructed model is still an intermediate model in the process of system developments; the model will be corrected, modified, and enhanced further by designers. Therefore, we also have to consider readability of the constructed model. In this paper, we proposed a method to construct state machine models from choreographies described by a set of communication diagrams using Petri nets. The proposed method will try to use the composite states and the orthogonal regions of UML state machines for the readability.