Interoperability of Message-Based Service Interaction

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  • Contact
    • Katharina Mehner (Siemens) -
  • Overview

    • Services operate by exchanging messages with each other. Each service needs to understand each others’ messages completely and unambiguously. 

      Services, however, are developed independently according to different standards and techniques. Furthermore, the same standards are often used in different ways. This jeopardizes the interoperability between services.
  • Problem Statement

    • Interoperability of message exchange is concerned with (data) format interoperability, protocol interoperability and most importantly the semantics of these messages. Interoperability is also concerned with higher level, but still application and domain independent protocols that describe how sequences of messages are interrelated, for instance, if they are defining transactions or sessions.
      In the presence of standards, interoperability is often impeded by ambiguities and incomplete specifications. Here, additional constraints or new versions are used to unify and formalize the intent of a standard. The former approach is, e.g., adopted by WS-I. As an example of the latter, SOAP 1.2 excludes certain elements in the body that SOAP 1.1 missed to prohibit. 
      Regarding higher level protocols, standards are not commonly adopted or are still missing and best practices vary a lot. In particular, sessions are implemented using very different standards.

      In the absence of standards or in the presence of conflicting standards, interoperability becomes a mediation challenge. Messages and protocols have to be transformed. In practice, tools like ESB (Enterprise Service Bus) or SCA (Service Component Architecture) runtime environments provide transformations between different messages and protocols, thereby aiming at hiding the use of different communication mechanisms. Nevertheless, interoperability remains a problem in practice because different vendors, which address varying business domains, adopt standards to a different extent. In such situations, best practices and respective patterns are needed.
  • Scope
    • The scope of this call is interoperability related to the exchange of single messages and to the exchange of a set of interrelated messages. It addresses standards for data formats, for message formats and for application and domain independent protocols together with the necessary mediation. It does not cover domain specific high level process protocols. 
  • Contributions
    • Contributions to this call are expected in the area of standards; constraints for standards; and cross-standard mediation (which is needed when interacting services use different but overlapping standards). We expect best practice patterns and constraints on patterns for mediation. Here, we expect documentation and analysis of the different existing solutions for a given problem/requirement, including a discussion of the lack of standards or the weaknesses of existing ones that gave rise to these solutions. The contribution is further expected to include a thorough analysis of the essential commonalities and variabilities of the involved patterns.
  • Baseline
    • The primary focus of this call is on web services. We ask for general solutions that can be applied to web services and WSDL.