Uwe Kylau

Towards a Unified Service Description Language for the Internet of Services: Requirements and First Developments

Service-oriented Architectures (SOA) and Web services leverage the technical value of solutions in the areas of distributed systems and cross-enterprise integration. The emergence of Internet marketplaces for business services is driving the need to describe services, not only from a technical level, but also from a business and operational perspective. While, SOA and Web services reside in an IT layer, organizations owing Internet marketplaces are requiring advertising and trading business services which reside in a business layer. As a result, the gap between business and IT needs to be closed. This paper presents USDL (Unified Service Description Language), a specification language to describe services from a business, operational and technical perspective. USDL plays a major role in the Internet of Services to describe tradable services which are advertised in electronic marketplaces. The language has been tested using two service marketplaces as use cases.

A unified description language for human to automated services

Through the rise of cloud computing, on-demand applications, and business networks, services are increasingly being exposed and delivered on the Internet and through mobile communications. So far, services have mainly been described through technical interface descriptions. The description of business details, such as pricing, service-level, or licensing, has been neglected and is therefore hard to automatically process by service consumers. Also, third-party intermediaries, such as brokers, cloud providers, or channel partners, are interested in the business details in order to extend services and their delivery and, thus, further monetize services. In this paper, the constructivist design of the UnifiedServiceDescriptionLanguage (USDL), aimed at describing services across the human-to-automation continuum, is presented. The proposal of USDL follows well-defined requirements which are expressed against a common service discourse and synthesized from currently available servicedescription efforts. USDLs concepts and modules are evaluated for their support of the different requirements and use cases.

An Overview of the Unified Service Description Language

Existing service description languages focus mainly on the technical aspects of automated services, hence all other types of service — namely human and IT supported — and the business aspects of service provision — pricing for instance — are yet to be adequately addressed. This paper introduces the latest version of the Unified Service Description Language (USDL), a domain-independent service description language aimed at all of the above-mentioned types of service, from both a business and a technical perspective. For the latter is already captured by widely adopted service description standards, such as WSDL and WS-BPEL, USDL does leverage those languages. Apart from aggregating technical information, a service provider can use USDL to describe business-related properties, capabilities and non-functional characteristics, enabling consumers to invoke and use business services and intermediaries to repurpose services. USDL has been developed mainly by SAP Research, which is driving its standardization with other stakeholders. This paper gives an overview of the USDL language and presents an editor to define and serialize USDL service descriptions.

Design Overview of USDL

Enabling Web-based service networks and ecosystems requires a way of describing services by a “commercial envelope” as discussed in Chapter 1. A uniform conception of services across all walks of life (including technical services) is required capturing business, operational and technical aspects. Therefore, our proposed Unified Service Description Language (USDL) particularly draws from and generalizes the best-of-breed approaches presented in Part I. The following chapter presents the design rationale of USDL where the different aspects are put in a framework of descriptions requirements. This is followed by the subsequent chapters of this part that provide details on specific aspects such as pricing or legal issues.

Service Functionality and Behavior

One of the most essential parts of every service description language is to provide suitable means for describing the following three aspects of services: (1) what the service does, i.e., which functionality it provides, (2) where the service resides, i.e., where it can be accessed and via which means it can be consumed, and (3) how the service behaves, i.e., how to interact with the service in order to properly consume it. These are subject to various existing and well established standards. In order to capture these aspects in an all-embracing manner, USDL defines three separate modules —the Functional, the Technical, and the Interaction Module — that each cover one aspect and together provide a holistic description of the functionality and behavior of services. The modules are commonly designed to provide a unifying description structure that abstracts from details and allows for the re-use and integration of existing as well as upcoming standards, thereby maintaining flexibility and extensibility of USDL. This chapter introduces the background and underlying design principles, and presents the USDL modules for functional, technical, and behavioral service descriptions in detail.