 server as part of an HTTP (or other protocol) request, and it is up to the server to decide how to use the user agent profile to best meet the needs of the user agent client. The two primary ways in which a profile might be used are selection and transformation. Selection is the process by which the originating server chooses an appropriate representation of requested web content from a finite set of existing representations. Transformation, on the other hand, assumes that there is no finite set of representations, but that content is flexibly created based on the properties expressed by the user agent profile. The content would be stored in an XML-compatible format and then transformed into an appropriate language (or modules thereof) that could be understood and optimized for the user agent, such as XHTML or WML. Negotiation can include information on the user agent's capabilities (physical and pro- grammatic); the user's specified preferences within the user agent's set of options; and Understanding Changing Telecommunications - Building a Successful Telecom Business TE MT End-to-end bearer service Local bearer GPRS/UMTS bearer service External bearer Radio access bearer (RAB) Core network (CN) bearer Radio bearer lu bearer Backbone bearer Physical radio Physical bearer UMTS core Fixed UTRAN network network CN edge Remote gateway terminal equipment equipment Figure 7.20 Many bearer services are part of the UMTS system, provided there are choices, suitable bearers are negotiated, especially the RAB bearer across the radio access specific qualities about the user agent that can affect content processing and display, such as physical location. See Figure 7.20. CC/PP is designed to work with a wide variety of web-enabled devices, such as PDAs, desktop machines, laptops, WAP phones, phone browsers, web television units and spe- cialized browsers for users with disabilities. Proxies may also be used to provide markup transformation, transmission or caching services for CC/PP-enabled clients and servers. 7.7 IMPLEME