Beyond Web Surfing— Content Services

Content-processing services (content services) are the functional components of content networks developed to solve the problem of customizing services. These processing services include creation, modification, conversion, or filtering of either content or requests for content. While such services have typically been provided at Web servers, newly defined elements called “service engines” allow these content-processing services to be provided on components within the network. Moving not only content closer to the user but also the services operating on it is a next logical step in the evolution of content networks. This chapter describes several approaches that are emerging to provide content-processing services. The chapter describes the technical and business forces that stimulate the creation of value-added service offerings in content networks, along with an overall architecture for distributing services, using intermediaries to steer selected requests and responses to service engines. Two examples of the distributed-services architectures—the Internet Content Adaptation Protocol (ICAP) and the Open Pluggable Edge Services (OPES)—are discussed in the chapter. The Web services approach to announcing, discovering, describing, and making use of Web services is introduced in the chapter. The Universal Description, Discovery & Integration (UDDI) specification, the Web Services Description Language (WSDL), the Simple Object Access Protocol (SOAP), and the Extensible Markup Language (XML) backplane they rely on are also described in the chapter.