Multiparty sessions in SOC

Coordination Models and Languages, 2008

We present a formal model for the coordination of interactions in service-oriented systems. This model provides a declarative semantics for the language SRML that is being developed under the FET-GC2 project SENSORIA for modelling and reasoning about complex services at the abstract business level. In SRML, interactions are conversational in the sense that they involve a number of correlated events that capture phenomena that are typical of SOC like committing to a pledge or revoking the effects of a deal. Events are exchanged across wires that connect the parties involved in the provision of the service.

… of the Theory and practice of …, 2008

2001

We distinguish between two broad categories of e-services: discrete services (e.g., add item to shopping cart, charge a credit card), and sessionoriented ones (teleconference, collaborative text chat, streaming video, ccommerce interactions). Discrete services typically have short duration, and cannot respond to external asynchronous events. Session-oriented services have longer duration (perhaps hours), and typically can respond to asynchronous events (e.g., the ability to add a new participant to a teleconference). When composing discrete e-services it usually suffices to use a process model and engine that composes the e-services as relatively independent tasks. But when composing session-oriented e-services, the engine must be able to receive asynchronous events and determine how and whether to impact the active sessions. For example, if a teleconference participant loses his wireless connection then it might be appropriate to trigger an announcement to some or all of the other participants. In this paper we propose a process model and architecture for flexible composition and execution of discrete and session-oriented services. Unlike previous approaches, our model permits the specification of scripted "active flowcharts" that can be triggered by asynchronous events, and can appropriately impact active sessions. We introduce here a model and language for specifying process schemas (essentially a collection of active flowcharts) that combine multiple e-services, and describe a prototype engine for executing these process schemas.

Science of Computer Programming, 2012

In this paper, we provide a mathematical semantics for a fragment of a language -SRML-that we have defined in the IST-FET-GC2 Integrated Project SENSORIA for modelling service-oriented systems. The main goal of this research is to make available a foundational basis for the development of practical modelling languages and tools that designers can use to model complex services at a level of abstraction that captures business functionality independently of the languages in which services are implemented and the platforms in which they execute. The basic artefact of the language is the service module, which provides a model for a complex service in terms of a number of components that jointly orchestrate a business function and may dynamically discover and bind to external parties that can deliver required functionalities. We define a mathematical model of computation and an associated logic for service-oriented systems based on the typical business conversations that occur between the parties that deliver a service. We then define the semantics of SRML service modules over this model and logic, and formulate a property of correctness that guarantees that services programmed and assembled as specified in a module provide the business functionality advertised by that module. Finally, we define an algebraic operation of composition of service modules that preserves correctness. To the best of our knowledge, there is no other formal approach that has been defined from first principles with the aim of capturing the business nature of service conversations and support service assembly based on the business logic that is required, not as it is programmed.

2006

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 requestresponse 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.