Device Description Repository
The Device Description Repository is a concept proposed by the World Wide Web Consortium (W3C) Device Description Working Group (DDWG). The proposed repository would contain information about Web-enabled devices (particularly mobile devices) so that content could be adapted to suit. Information would include the screen dimensions, input mechanisms, supported colors, known limitations, special capabilities etc.
The DDWG, operating as part of the W3C Mobile Web Initiative (MWI), was chartered to "foster the provision and access to device descriptions that can be used in support of Web-enabled applications that provide an appropriate user experience on mobile devices." Mobile devices exhibit the greatest diversity of capabilities, and therefore present the greatest challenge to content adaptation technologies. The group published several documents, including a list of requirements for an interface to a Device Description Repository.
The idea of implementing a Device Description Repository was discussed at an international workshop held by the DDWG in Madrid, Spain in July, 2006. This resulted in a proposal to re-charter DDWG to work on the formal design of the programming interfaces, and ways to populate the repository with data and make this available to anyone who wanted to build Web servers that could adapt content to suit the end user devices.
The architecture of the repository has not been clarified, but a distributed solution is likely. In general, the desirable characteristics of a Device Description Repository are:
- Relevance of data. The DDWG includes content adaptation specialists who have identified a core set of device properties that are useful for adaptation. Other groups are likely to refine this knowledge. Keeping the information up-to-date will also be a challenge.
- Ease of use. The interfaces should map easily to a variety of programming languages, and be as simple to use as other popular adaptation technologies (e.g. WURFL).
- Ease of deployment. Existing technologies like DNS show that global repositories can be deployed on a real-time basis. The W3C is unlikely to specify a particular server architecture. The DDWG has already identified a Web Services interface (e.g. SOAP) as a minimum requirement, and implementations are free to create the logic any way they wish (e.g. relational database queries) so long as the formal interface is supported.
- Assured interoperability. The varied nature of the Web requires that the repository interfaces and data formats can be supported by the largest number of Web technologies. Formal descriptions of APIs and Data Vocabularies will be necessary.
- Assured availability. If Web servers rely on device descriptions to provide adapted content, then these descriptions must be available at all times. Multiple repository hosts and support for data caching are likely to be part of the repository architecture.
- Efficiency. To ensure that the repository does not create unnecessary burden on scarce resources, the load should be distributed and data formats should be designed for simple processing.
- Industry support. The backing of organisations like W3C and the Open Mobile Alliance, and of vendors, service providers and device manufacturers will be critical.