Handbook of Service Description

For some time, increasing importance is attached to services, both from an economical and a managerial perspective. First, the notion of “service as basic unit of exchange” emphasizes the application of specialized competencies for the benefit of someone else, while disregarding if a physical good or any other resource is used for exchanging value. Second, service-orientation allows enterprises to enter new markets by extending their existing portfolio of products by related services or realizing entire new offerings that are enabled by recent advances in information technology. Service description is a key challenge in developing and providing services to and with customers. Further it is a premise for coordinating several providers of an integrated customer solution. This chapter is an effort to explain how conceptual modeling can facilitate service description. We use Product-Service Systems (PSS) as an exemplary domain.We extract central concepts from several disciplines that are engaged in researching business aspects of PSS to develop a catalogue of modeling requirements to be accounted for in service description. Consecutively, these requirements are utilized to assess the current state of conceptual modeling languages for (product-related) service description. The review leads to the identification of further prospects to be accounted for by service description.

This chapter discusses several approaches to design, analyze, describe and compose service networks.We analyze the technical and business-related aspects of these approaches, their evolution, and the trends they will be likely to follow. We further suggest how the two major trends driving these approaches (i.e., business and process orientation) can converge. The chapter concludes with a discussion of future lines of research in this area.

As the service-oriented architecture paradigm has become ever more popular, different standardization efforts have been proposed by various consortia to enable interaction among heterogeneous environments through this paradigm. This chapter will overview the most prevalent of these SOA approaches. It will first show how technical services can be described, how they can interact with each other and be discovered by users. Next, the chapter will present different standards to facilitate service composition and to design service-oriented environments in light of a universal understanding of service orientation. The chapter will conclude with a summary and a discussion on the limitations of the reviewed standards along their ability to describe service properties. This paves the way to the next chapters where the USDL standard will be presented, which aims to lift such limitations.

The research area of Semantic Web Services investigates the annotation of services, typically in a SOA, with a precise mathematical meaning in a formal ontology. These annotations allow a higher degree of automation. The last decade has seen a wide proliferation of such approaches, proposing different ontology languages, and paradigms for employing these in practice. The next chapter gives an overview of these approaches. In the present chapter, we provide an understanding of the fundamental techniques, from Artificial Intelligence and Databases, on which they are built. We give a concise, ontology-language independent, overview of the techniques most frequently used to automate service discovery and composition.

Semantic Web Services aim to better support the life-cycle of Web services and service-based applications by exploiting semantic descriptions of services. Research in this field has been considerably active and has produced a large number of ontologies, representation languages, and integrated frameworks supporting the discovery, composition and invocation of services among other tasks. In this chapter we provide a thorough, albeit necessarily brief, overview of the conceptual models devised so far, giving the reader a perspective on the relationships, coverage and applicability of each of them together with pointers for gathering further insights and details about these solutions and related software.

The on-line discovery, trading and consumption of services as envisioned in the Internet of Services demand an advanced support of the business aspects. Pricing plays a fundamental role among such business facets on both sides of a service marketplace. This chapter discusses the scientific background of the USDL Pricing Module as a comprehensive, applicable, executable, and non-proprietary endeavor. As such, the chapter elicits what makes modeling and engineering the price of a service transaction less straightforward than in the case of a product sale. In addition, we review the state of the art with regard to price meta-models and give a detailed explanation of the most differentiating design choices in the meta-model we propose, including the interdependencies with other USDL modules.

Service marketplaces and service networks promote tradeable services on the Internet. With such business transactions the need for legal certainty and legal compliance arises. Two crucial aspects can be highlighted in this context: you need to know about what you are talking and under which jurisdiction a transaction is arranged. Both aspects are difficult to address in a machine-processable description for services. The subject matter–the what–is difficult to grasp: the service notion in USDL encompasses technical Web services to conventional business services. Furthermore, machine-processable legal attributes need to comply to the statutes of the respective country of the transaction in order to achieve enforceable legal expressions. Current models apply approaches which do not address the aforementioned aspects. We argue to overcome the difficulties by modeling legal description capabilities on the basis of the statutes. This chapter covers the modeling of licensing aspects according to two different jurisdictions. We use the copyright acts of Germany and the USA to illustrate the approach. The resulting model incorporates the terms of the statutes, for example, Work, which can be mapped to any licensable service artifact. Although certain notions such as Work have a common semantic understanding this approach requires a management of the different variants. Variants are discussed in Chapter 17.

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.

This chapter covers the scientific background for the Service Level Module of the Unified Service Description Language (USDL). In addition to general service level concepts, we expand on two specific service level fields: security and trust. For that end we first review the state of the art in service level modeling, then we explain the design of the Service Level Module and position it among the rest of USDL. For security, two possible perspectives, a high level business view and a low level engineering approach, are introduced. With regards to trust, USDL is suitable to specify how a service can be rated by its consumers and to ensure that ratings of competing services are comparable, and hence to determine trustworthiness. Additionally, we present a description of non-security-related elements that can be exploited for trust estimation.

One of the basic purposes of USDL is to provide a “commercial envelope” around a service for exposition in Web-based service networks (i.e., the Internet of Services). Besides the description of pricing, licensing, functionality, behavior, service levels, and security aspects, there remain the following fundamental facets: the interweaving of all the aspects, the modeling of basic concepts such as service, composite service, or bundles, and the information about participants in the delivery of the service. These concepts are reflected in the modules introduced in this chapter: the Service Module and the Participants Module. These two modules are complemented by the Foundation which covers aspects that are used in multiple other modules. This chapter presents the module design taking into account the influence of the state of the art and several of the general language requirements as well as the service concept formation requirements from Chapter 8.

This chapter deals with technical aspects of how USDL service descriptions can be read from and written to different representations for use by humans and tools. A combination of techniques for representing and exchanging USDL have been drawn from Model-Driven Engineering and Semantic Web technologies. The USDL language’s structural definition is specified as a MOF meta-model, but some modules were originally defined using the OWL language from the Semantic Web community and translated to the meta-model format. We begin with the important topic of serializing USDL descriptions into XML, so that they can be exchanged between editors, repositories, and other tools. The following topic is how USDL can be made available through the Semantic Web as a network of linked data, connected via URIs. Finally, consideration is given to human-readable representations of USDL descriptions, and how they can be generated, in large part, from the contents of a stored USDL model.

Fundamental tooling is required in order to apply USDL in practical settings. This chapter discusses three fundamental types of tools for USDL. First, USDL editors have been developed for expert and casual users, respectively. Second, several USDL repositories have been built to allow editors accessing and storing USDL descriptions. Third, our generic USDL marketplace allows providers to describe their services once and potentially trade them anywhere. In addition, the marketplace software can be customized to different settings and considers the idiosyncrasies of service trading as opposed to the simpler case of product trading. The chapter also presents several deployment scenarios of such tools to foster individual value chains and support new business models across organizational boundaries.We close the chapter with an application of USDL in the context of service engineering.

The previous chapter introduced service marketplaces as fundamental tool that enables and benefits service ecosystems. The application of service marketplaces for enterprise resource planning is a growing market. The operation of such an online marketplace requires a governance approach that lies adjacent to the requirements of a SOA and the more general governance of IT. It also has requirements of its own, especially when it comes to the description of services with languages such as USDL. In this chapter, we propose four building blocks as a basis for a governance framework that is capable of supporting the operation of a service marketplace. The research is based on existing frameworks and also takes into consideration the particularities of emerging SOA Governance approaches. We emphasize the processes required for the management of service descriptions.

Different variants of USDL are required for different contexts. This is already shown by the Legal Module which requires different contents depending on the jurisdiction of a country. The issue aggravates if more and more parameters are relevant to determine the correct variant. The chapter presents one possible solution for variant management consisting of a canonical data model, a context driver mechanism, governance processes, and appropriate tooling. Although the solution for variant management is targeted at existing business documents, such as a purchase order, it provides a powerful and adequate means for dealing with USDL variants as well.

Case studies play an important role for validations in general. In particular, they are the first step to a comprehensive validation of USDL, because they can create feedback regarding usability, feasibility, completeness etc. of certain aspects of USDL. This chapter contains the findings of executing four different case studies: services in the energy domain, services for mobile users, manual services for insurances, and services for B2B integration. Each case study originates from a different company and provides its own conclusion. In general, the case studies show that USDL can be used to realize the described scenarios. However, they identify also room for improvement: the scope of USDL should be limited (don’t try to be “universal”), semantic technologies should be used, and a simple API is necessary.

The Internet of Services promotes distributable, composable and tradeable services as first-class entities. Such services are assumed to encompass the full range from technical Web services to conventional business services delivered by humans. However, research and development of service models and platforms to realize the Internet of Services vision has largely been concentrating on pure technical services. With the introduction of the Unified Service Description Language (USDL), this is about to change. In a multiple-enterprise evaluation study performed in parallel to the ongoing USDL specification process, we have applied modeling and registration techniques to existing services with none or few technical components provided by businesses in a locality-constrained area with the purpose of determining suitability and acceptance aspects. We outline the results of our study and include an evaluation of USDL language facilities in the context of real-world service representation. This chapter connects evaluation results with early USDL drafts [16] with a discussion on recent USDL capability changes up to the specification milestone M5.

The USDL has been designed as a means to describe services so that they can be traded via the Internet. The previous parts outlined the status-quo of service description research and practice and highlighted by feature comparison that USDL outstands related approaches in various concerns. However, for evaluating the actual worthiness of a modeling language such as USDL, potential users will consider the fit of the language with the contingent influences their organizations have to deal with. To fill this gap, the purpose of this chapter is to identify requirements for a service description language from potential USDL users. The presented research takes a semiotic theory perspective to the design of modeling languages. Through a Delphi study approach, i.e., an anonymous, written multi-stage survey process, the chapter elaborates a set of requirements. The requirements can be used to ex-post test if the features of the USDL actually address the users’ needs and to recheck the underlying assumptions of the USDL design and development process. While finding broad consent with most requirements, we also observed differentiated needs related to the intended use of the USDL.

The USDL aims at providing comprehensive descriptions of business and software services which cover all aspects relevant to support their discovery and combination in the envisioned Internet of Services. In this chapter, we specifically evaluate the expressive power of USDL to specify software services. Based on an analysis of literature on software description requirements and related approaches, we derive a theoretically grounded evaluation framework. This framework is used as a benchmark to evaluate the constructs of the USDL. According to the presented evaluation framework, comprehensive descriptions of software services should cover commercial information, implemented business semantics, technical binding information, and service quality. The evaluation shows that the USDL provides the most detailed approach to date to comprehensively describe software services, which nevertheless should be harmonized in some aspects.