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This is the High-level DDR functional requirements of the document. See the DeviceDescriptionRepositoryRequirements overview.

High-level DDR functional requirements


* The DDR API must, at a minimum, support

  1. identification of components of the delivery context
  2. the retrieval of device descriptions


The following are motivated by the use cases:

[DDR API] The DDR MUST expose an API through which device descriptions can be retrieved.

[DDR-MEASUREMENT] If a value returned by the DDR is an indication of measurement (such as width or resolution) then the units of measurement are expected to be unambiguous to the requesting party: i.e. either the vlaue returned explicitly declares the measurement unit, or the requesting party specifically asked for the value in a particular unit ('screen width in cm').

[DDR-CONTEXT-KEY] The DDR is expected to attempt to return a device description (or element thereof) based on identification of the hardware and/or software that the description relates to (the 'context key').

[DDR-INSUFFICIENT-CONTEXT-EXCEPTION] The DDR is expected to follow exception handling requirements as detailed in the DDRAPI document.

[DDR-VALUE-RANGE] The DDR is expected to return a range of all known values of a particular device capability for a given context key if requested to do so.

[DDR-CONTEXT-AMBIGUITY] Should the DDR not receive enough information to accurately determine the context key, then it is expected to either (a) make a 'best effort' guess based on the evidence available, (b) return all possible values for the aspects of the description queried, or (c) return an exception as detailed in the DDR-API document

The following requirement is a goal of the DDWG:

[DDR-TECHNOLOGY] It MUST be possible to realize the DDR and its exposed interfaces through different technologies including but not limited to Web services.