Information about non-functional properties (NFPs) is rarely explicitly described in Service Oriented Architecture (SOA) services. In particular, there is still no standardized solution addressing what service providers should expose or advertise as NFPs in service descriptions to empower service consumers to decide whether a given service suits best their needs or not. Our goal is to define a catalogue of generic (i.e., domain independent) nonfunctional properties to be considered when service descriptions are developed. This catalogue should be used to better characterize services and enable consumers to perform advanced applications such as NFP-aware service selection. We have identified an initial catalogue of SOA-related NFPs that are relevant from the perspective of consumers (as opposed to providers). Then, we have designed an online survey and invited international SOA experts in many application areas to criticize the relevance and definitions of the proposed NFPs and to enhance this catalogue. After analyzing the survey results to synthesize an improved catalogue, we have validated the new definitions a second time with a subset of the initial participants. We obtained a validated list of 17 NFP definitions for atomic SOA service descriptions relevant from a service consumer's perspective.

Service engineering is the process of service development from domain analysis and requirements capture, through specification, design and implementation, to deployment and adaptation on service delivery platforms. Ideally one would like to specify and analyse services on a high level of abstraction, using modelling concepts close to the user and problem domain rather than at the platform and implementation domain, and then be able to derive design components and implementations from service models with a high degree of automation. It is argued in this paper that this conception is approaching reality and so is worth while pursuing to face the challenges of service engineering in a NGN context. The basis for this is new approaches to model services precisely, to analyse goals and tradeoffs concerning variability and context, and to transform service models into platform independent models from which implementations are automatically generated. Interestingly, the service models can provide information and mechanisms that help dynamic composition and adaptation at runtime. The approach is illustrated using a multimedia call service with access control requirements.

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Non-functional properties (NFPs) represent an important facet of service descriptions, especially in a Service Oriented Architecture. Yet, they are seldom explicitly described, and their use in service selection and composition is still limited. This chapter presents the User Requirements Notation (URN) as a means to model and analyze functional and non-functional service requirements. Aspect-oriented extensions to URN (AoURN) enable the modeling and modularization of different concerns, including non-functional requirements, which can crosscut services or service components. The chapter also proposes a taxonomy of NFPs used to annotate services and service compositions modeled with AoURN. These annotations enable the specification of quantitative non-functional values for services, guide service selection, and support the computation of the NFP (e.g., the quality of service) of their composition. This approach is illustrated with a simple yet realistic composite service (BookItWell), with an emphasis on four types of NFPs, namely service cost, response time, reliability, and availability.