Abstract. A service choreography is a model of the interactions in which a set of services engage to achieve a goal, seen from the perspective of an ideal observer that records all messages exchanged between these services. Choreographies have been put forward as a starting point for building service-oriented systems since they provide a global picture of the system’s behavior. In previous work we presented a language for service choreography modeling targeting the early phases of the development lifecycle. This paper provides an execution semantics for this language in terms of a mapping to π-calculus. This formal semantics provides a basis for analyzing choreographies. The paper reports on experiences using the semantics to detect unreachable interactions. 1

Abstract. In scenarios where a set of independent business partners engage in complex conversations, global interaction models are a means to specify the allowed interaction behavior from a global perspective. In these models atomic interactions serve as basic building blocks and behavioral dependencies are defined between them. Global interaction models might not be locally enforceable, i.e. they specify constraints that cannot be enforced during execution without additional synchronization interactions. As this property has only been defined textually so far, this paper presents a formal definition. For doing so, this paper introduces interaction Petri nets, a Petri net extension for representing global interaction models. Algorithms for deriving the behavioral interface for each partner and for enforceability checking are provided. 1

Abstract. Process choreographies describe interactions between different business partners and the dependencies between these interactions. While different proposals were made for capturing choreographies at an implementation level, it remains unclear how choreographies should be described on a conceptual level. While the Business Process Modeling Notation (BPMN) is already in use for describing choreographies in terms of interconnected interface behavior models, this paper will introduce interaction modeling using BPMN. Such interaction models do not suffer from incompatibility issues and are better suited for human modelers. BPMN extensions are proposed and a mapping from interaction models to interface behavior models is presented. 1

Foreign exchange (FX) markets see a transaction volume of over $2 trillion per day. A number of standard ways of conducting business have been developed in the FX industry. However, current FX specifications are informal and their business semantics unclear. The resulting implementations tend to be complex and compliance with the standards unverifiable. This results in potential loss of value due to incompatible business processes and possible trades not consummated. This paper validates a formal, protocol-based approach by specifying foreign exchange processes as standardized by the TWIST consortium. The proposed approach formalizes a small, core set of foreign exchange interaction protocols on which the desired processes can be based. The core protocols can be composed to yield a large variety of possible processes. Each protocol is rigorously defined in terms of the commitments undertaken and manipulated by the parties involved. By contrast, traditional approaches as used in the current TWIST specification lead to redundancy in specification and difficulty in understanding the import of the interactions involved. In addition, our approach discovered interesting business scenarios that traditional approaches would have missed. 1

Abstract. Interacting services are at the center of attention in businessto-business (B2B) process integration scenarios. Global interaction models specify the interaction behavior of each service and serve as contractual basis for the collaboration. Consequently, service implementations have to be consistent with the specifications. Consistency checking ensures that an implemented service is compatible with other services, i.e. that it can interact successfully with them. This is important in order to avoid deadlocks and guarantee proper termination of a collaboration. Different notions of compatibility between interacting services and consistency between specification and implementation are available but they are typically discussed independently from each other. This paper presents a unifying framework for compatibility and consistency and shows how these two notions relate to one another. Criteria for an optimal consistency relation with respect to a given compatibility relation are presented. Based on these criteria weak bi-simulation is evaluated. 1

Capturing the interaction behavior between two or more business parties has major importance in the context of business-tobusiness (B2B) process integration. The Business Process Modeling Notation (BPMN), being the de-facto standard for modeling intra-organizational processes, also includes capabilities for describing cross-organizational collaboration. However, as this paper will show, BPMN fails to capture advanced choreography scenarios. Therefore, this paper proposes extensions to broaden the applicability of BPMN. The proposal is validated using the Service Interaction Patterns.

Abstract. Recent approaches to service-oriented systems engineering start by capturing the interactions between services from the perspective of a global observer, leading to so-called service choreographies. The rationale is that such choreographies allow stakeholders to agree on the overall structure and behaviour of the system prior to developing new services or adapting existing ones. However, existing languages for choreography modelling, such as WS-CDL, are implementation-focused. Also, these proposals treat choreographies as monolithic models, with no support for multiple viewpoints. This paper proposes a multi-staged and multi-viewpoint approach to choreography modelling. For the initial stages, the approach promotes the partitioning of choreography models and the design of role-based views; while for subsequent stages, milestone and scenario models are used as an entry point into detailed interaction models. The paper presents analysis techniques to manage the consistency between viewpoints. The proposal is illustrated using a sales and logistics model. 1

Abstract. This paper shows how companies can use product-centric data to locally represent the interactions with and between their partners. An agent-based interaction modeling language is used to capture these interactions graphically and formally. Moreover, a formal method is introduced that enables partners to automatically construct a global interaction diagram from their local interaction representations. This global interaction diagram improves enterprise interoperability, since it increases overall process visibility. A simple process example is used to illustrate the approach.

Abstract. A choreography describes the interaction between services. It may be used for specification purposes, for instance serving as a contract in the design of an interorganizational business process. Typically, not all describable interactions make sense which motivates the study of the realizability problem for a given choreography. In this paper, we show that realizability can be traced back to the problem of controllability which askes whether a service has compatible partner processes. This way of thinking makes algorithms for controllability available for reasoning about realizability. In addition, it suggests alternative definitions for realizability. We discuss several proposals for defining realizability which differ in the degree of coverage of the specified interaction. 1

This paper discusses the notion of protocol compatibility between Web services, and reviews a number of techniques for detecting incompatibilities and for synthesizing adapters for otherwise incompatible services. The paper also reviews related notions such as realizability, substitutability and controllability. 1