Device Independent Authoring Language (DIAL) Part 0: Primer

W3C announced that the Ubiquitous Web Applications Working Group has
published a Working Draft for DIAL Part 0: Primer, updating the earlier
document of 2006-10-10. This document provides an introduction to, and
the benefits of, DIAL (the Device Independent Authoring Language). The
most recent DIAL specification Working Draft (2007-07) defines a
markup language for the filtering and presentation of Web page content
available across different delivery contexts. This will facilitate an
optimal user experience following adaptation of the DIAL instance document.
DIAL is a language profile based on existing W3C XML vocabularies and
CSS modules. These provide standard mechanisms for representing Web page
structure, presentation and form interaction. The DIAL also makes use of
the DISelect metadata vocabulary ("Content Selection for Device
Independence -- DISelect") for overcoming the authoring challenges
("Authoring Challenges for Device Independence") inherent in authoring
for multiple delivery contexts. The DIAL Primer summarizes the concept
of device independence, the scenarios in which it could be used, and
the considerations in order to achieve that goal. It then describes the
role of DIAL in ensuring the delivery of content suitable for the user,
device and inherent circumstances in which it was requested. DIAL
facilitates writing a Web page that can be presented by a range of
devices, with differing capabilities and states; and consumed by users
with differing preferences and entitlements (such varying conditions
are illustrated in 'Delivery context characteristics'). This is achieved
by allowing authors to declare authorial intent as to the conditions
under which content should be chosen or filtered. When a request is made
for a DIAL document, it must pass through at least one DIAL processor
before being presented to the requesting user. DIAL processors may exist
at any of the server, optional intermediary adaptation, or client layers.
Their role is to determine whether to select or filter out blocks of
content marked up with DISelect expressions. The evaluation of these
expressions requires the processor to query the Delivery Context so
that the decision to select or filter content involves the specific
conditions under which the request was made. After all DIAL processing
is complete, all content selections will have been resolved. Since
DIAL implements XHTML 2.0 metadata extensions, it allows other metadata
standards to be plugged in to allow content to be selected or excluded
for rendering based on variable business rules. These could include
flagging the nature of the content (such as erotic or violent), or by
indicating that it should only be shown in a certain location or time
of day. W3C's Ubiquitous Web Applications Working Group was chartered
through March 31, 2009, seeking to simplify the creation of distributed
Web applications involving a wide diversity of devices, including
desktop computers, office equipment, home media appliances, mobile
devices (phones), physical sensors and effectors (including RFID and
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