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Nokia Position Paper for W3C Workshop on Constraints and Capabilities for Web Services

Art Barstow
Frederick Hirsch
Michael Mahan
September 3, 2004

Nokia is interested in the issues regarding constrained devices given its position in the mobile industry. The separation between the expression of metadata and the mechanism of association with a particular interaction is an important one. Clarifying these facilities and forming an industry consensus on the driving requirements is essential in a networking world of heterogeneous processors, platforms, and communication networks. Furthermore, work on advancing an industry consensus on an overall framework to express and associate Web services constraints and capabilities is an endeavor that Nokia feels is worthwhile and worth participating in.

 - Nokia is interested in understanding different viewpoints regarding Web services policy mechanisms. For example, we recognize the advantages of a light-weight mechanism such as WS-Policy, yet also value open standards like XACML, which offers a general and powerful policy mechanism. We would like to understand other industry positions on these mechanisms and others.

 - Nokia is also interested in how description and extensibility relate to constrained devices, understanding WSDL approaches as well as others.

 - Nokia would like to learn of the performance studies others have done and the conclusions they have reached regarding deployed distributed systems featuring facilities to process constraints and capabilities during each messaging instance.

Nokia has been active in the domain of constraints and capabilities. Nokia has worked with the W3C to create CC/PP. CC/PP specifies a reasonable generic framework for describing “components” such as: a user's preferences, device physical capabilities, device software support, network characteristics, etc. If the Web service community needs such a framework, CC/PP should be considered. It is within the design center of CC/PP (via the extensibility of the RDF data model) for other communities to define their own domain-specific "components" which express their particular constraints and capabilities. Using such a CC/PP based framework, a new Web services based component could be added to a base profile  and thus the capabilities of the new component could be publicized (i.e. available to servers, intermediaries, etc.) without changing the initiator's software.

Nokia has also been instrumental in developing the Open Mobile Alliance’s User Agent Profile (UAProf) specification – an application of CC/PP. The core idea of the UAProf specification is to make device capability information available to different parties in order to get the best possible fit between content and the capabilities of a specific device.

Devices that support the UAProf architecture provide a URL in the WAP or HTTP session header. This URL points to an XML file that describes the profile of that device model. Nokia and other device vendors have their own public HTTP servers where service providers can download device profiles as standardized XML documents.

During the browsing session or MMS download, the device profile can be used to optimize presentation of the content. It can also be used in the dynamic service offering. For example, the user at a game site sees only the games that can be played with his device. The service provider can also adapt content by scaling a bitmap to fit the display size, for example, or reducing the size of an image or music file via resampling.

Most new Nokia devices support the UAProf architecture and Nokia has made their profiles publicly available. The Nokia Multimedia Messaging Solution and Nokia WAP Gateway can also make use of UAProf for content adaptation. Note that Nokia has shipped millions of phones that use UAProf and thus the W3C’s CC/PP based framework.

This use case, for maximal interoperability across device vendors and service providers, could instead use Web services technologies for associating capabilities and constraints to the services offered. Also, is a world of SOAP services rather than UI-oriented markup, providers will be serving SOAP messages rather than HTML. As mobile business realigns to this environment, the association of constraints and capabilities must use the extensibility mechanisms incipient with such Web services technologies such as SOAP and WSDL.