New standard for mobile web
W3C's new standard aids in delivering Web content
to broad range of devices
16 January 2004
The World Wide Web Consortium (W3C) announces the release of
the Composite
Capability/Preference Profiles (CC/PP): Structure and Vocabularies
1.0 Recommendation.
CC/PP 1.0 is a system for expressing device capabilities and
user preferences, using the Resource Description Framework (RDF).
Used to guide the adaptation of content, a CC/PP profile describes
device capabilities and user preferences.
A W3C
Recommendation is the equivalent of a Web standard, indicating
that this W3C-developed specification is stable, contributes to
Web interoperability, and has been reviewed by the W3C Membership,
who favor its adoption by the industry.
Device-independent Web needs better communication
between user devices and Web servers
One of the W3C's primary goals is Universal Access.
Users must be able to use their choice of devices to access Web
content, in ways that are appropriate for their hardware capabilities,
software, network infrastructure, native language, culture, geographical
location, or physical abilities. CC/PP provides a standardized
format of the description of information that will allow Web-enabled
devices to effectively communicate their capabilities to the desired
server.
In simple terms, it's been clear that there needed
to be a standard way for a cellphone or a personal digital assistant
with Web access to be able to say to a Web server, "I am
a cellphone. My display size will not allow me to see a framed
site. Please deliver the content in detailed lists instead."
This is an example of what is known as a "delivery context,"
where the device characteristics, user preferences, and constraints
put requirements on how content can be effectively displayed on
the device for the user.
This is precisely the purpose of CC/PP. CC/PP is an extensible
framework that can be used for communicating the delivery context
from a device to a Web server, resulting in the delivery of Web
content that is usable on a given device.
"CC/PP plays a vital role in supporting the ability of people
to access the Web from an increasingly diverse range of devices,"
explained Rhys Lewis, Chair of the W3C Device Independence Working
Group (DIWG) where CC/PP is being developed.
"There is now a huge variation in capability between, on
the one hand, the smallest, most portable, Web-enabled devices
and, on the other, the typical personal computers and workstations
that we've traditionally used. Between these extremes are many
other types of devices that can access the Web, including interactive
television systems, personal digital assistants, smart phones
and domestic appliances."
"By providing a stable framework for devices and Web servers
to optimize content delivery, CC/PP provides a foundation for
a device independent Web, and actual device empowerment,"
explained Lewis. "As CC/PP uses RDF for the actual descriptions,
we can foresee ease in sharing existing profiles, and more easily
combining and creating new ones as new devices appear on the market."
CC/PP Resolves Web Content Negotiation Problems
Content negotiation has been part of the Web for a long time
as part of the HTTP protocol. Its practical uses in content adaptation
have often been limited because HTTP was designed for browser
descriptions and not user, context and device descriptions. By
allowing complex and complete descriptions of all aspects of the
delivery context, CC/PP provides comprehensive information for
the process of customizing Web content to user needs.
CC/PP was designed at a time when mobile phones were emerging.
The specification takes into account their specific features,
particularly in bandwidth restriction. Thus, clients have the
choice of providing their CC/PP information as a link (URI) to
a description available on the Web, instead of providing the information
itself.
CC/PP Leverages the Semantic Web
CC/PP uses RDF, one of the key specifications of
the Semantic Web. It is the first W3C Recommendation that is also
an RDF application. The use of RDF for CC/PP has many advantages,
including
- Extensible vocabularies: In previous efforts to develop global
vocabularies it was very difficult to fix a set of terms that
could be used to describe all possible devices in advance -
there is always a device with capabilities that the language
designer cannot foresee. CC/PP solves exactly this sort of problem
through the use of the Semantic Web and RDF. With the CC/PP
framework, any device manufacturer can define a vocabulary description
that can be reused and extended easily.
- Non-centralized vocabularies: Another problem with traditional
device description languages is the need for central registries
for vocabularies - a device manufacturer has to go through a
registry to be able to use new device capabilities in device
descriptions. This may include a lengthy registration and standardization
process. With CC/PP and the Semantic Web, there is no need for
a central registry. New device capabilities can be defined by
anyone, and work seamlessly with existing capability definitions.
- Simple integration of information from different sources:
When adapting Web content for a specific user, the information
that is needed for the adaptation can come from different sources
- the network, the device, the environment or the user's preferences.
The server receives these different pieces of information separately,
and needs to merge the information into one model before doing
content adaptation. Based on the Semantic Web and RDF, CC/PP
makes this data integration easy.
CC/PP already playing a crucial role in the mobile Web
The User Agent Profile (UAProf) specification developed by the
Open Mobile Alliance (and formerly by the WAP Forum) is a CC/PP
vocabulary dedicated to mobile phone description. Today, mobile
phones complying with the UAProf specification provide CC/PP descriptions
of their capabilities to servers - literally millions of devices
are already using CC/PP.
JCP (the Java Community Process) has developed, in their JSR
188 expert group, a Java API for CC/PP which allows a Java Web
server to access and use CC/PP information provided by a client
device. With the release of this work in October 2003, one can
safely forecast a significant increase in the number of content
servers understanding and using CC/PP information.
Next steps include building protocol and processing rules, and
updating to include new RDF datatyping
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