As Web Services development grew rapidly since 2002, the need for Quality of Services (QoS) has become a significant factor for building a trustworthy service application. There have been many proposals and frameworks which adds QoS to Web Services. However, few technologies have survived the race and forced their way to standardization. This paper will explore some of what has been done in Web Services QoS in the last decade. Some of the questions answered in this paper are: Where exactly do we stand now in supporting QoS attributes representing non-functional requirements for Web Services? What technologies as well as QoS attributes have proven themselves to be worthy for standardization? Three main models and two main technologies will be discussed, i.e., Web Services Publishing & Discovery, Web Services Description & Handling, and the combination of both. These models are combined with two technologies: Universal Description Discovery and Integration (UDDI) and WS-Policy. This paper will show that many approaches introducing non-functional characteristics to Web Services have mainly considered security, reliable messaging, transaction, accounting, availability and response time as major quality characteristics for Web Services. This paper will conclude that policies has found popularity and acceptance among industry vendors.

We present a new approach for checking the compatibility of policy descriptions. At present, policies are widely used for explicitly expressing non-functional properties, capabilities, constraints and requirements of Web services. Policies are crucial in the negotiation phase of service discovery and selection. Typically, a potential service consumer has its own policy that specifies the conditions the service has to fulfill. Ideally, an automatic negotiation process identifies a mutually agreeable policy for both the Web service consumer and provider. WS-Policy defines policy intersection as a "first approximation" for determining the compatibility of policies. However, policy intersection has a major weakness: It is a purely syntactic approach neglecting the semantics of the involved policy assertions. In addition, it is unspecific on how to include domain-specific processing. In this paper we present a new solution that overcomes these deficits by introducing an entailment relation that reflects the semantics of assertions and policies. This paper not only discusses the formal foundations but also introduces the required algorithms such as "semantic policy differencing".

Today, Web services play a dominant role in Enterprise Application Integration (EAI) and for realizing Service Oriented Architectures (SOA), which define the architectural foundation for various kinds of distributed applications. In many business domains, Web services must exhibit quality attributes such as robustness, security, and maintainability. As a consequence, there is a high demand to develop Web services with Quality of Service (QoS) properties. Several specifications of the WS-* family, e.g. WS-Security and WS-Reliable Messaging, aim at simplifying the development and deployment of QoS-aware Web services. Although these approaches cover some typical application scenarios, their expressivity and flexibility are limited by the underlying WS-Policy framework. This paper proposes the syntax and semantics of a new WS-Policy operator that enables the introduction of conditional assertions. Secondly, a framework for managing different types of custom assertions is presented. Finally, this paper describes a proof of concept implementation demonstrating the practical feasibility of both extensions.