Expression language for accessing the delivery context

Contributors: José Manuel Cantera Fonseca, Telefónica I+D

Date: July 2008

Antecedents

The Delivery Context: XPath Access Functions 1.0 [1] CR defines a set of concrete functions intended to access certain Delivery Context properties using XPATH Expressions. Such functions can be used from XSLT sheets to adapt pages for multiple devices.

The DDR Simple API [2] is a Proposed Recommendation (it will be very soon) that defines an API for getting property values for different Delivery Context Aspects.

In addition there is an upcoming proposal about Device Groups ready to be published by the DDWG [3].

Proposal

To deprecate [1] in favour of a more generic function to retrieve any property value in accordance with [1] and aligned with the expression language defined in [3].

Examples

     dcn:evaluate('[webBrowser,supportedImageformats]')

     dcn:evaluate('[device,displayWidth]')

Issues

• How to indicate vocabulary prefixes
• How to indicate units (although the DDR Simple API does not support units)
• Sometimes the function returns an enumeration while others it returns a single value, do we need only a function or do we need more?

[1] http://www.w3.org/TR/cselection-xaf

[2] http://www.w3.org/TR/DDR-Simple-API/

[3] http://www.w3.org/2005/MWI/DDWG/drafts/structures/DDR-Structures.html