W3C Workshop on
Device Independent Authoring Techniques
Developing Device Independent
Java Applications with JSR 188
Luu Tran
Sun Microsystems, Inc.
luu.tran@sun.com
Abstract
The Java Community ProcessSM (JCP) [1] is the way the Java platform evolves. Java
Specification Request (JSR) 188 [2] was recently
submitted to the JCP [1] to enable interoperability
between web servers and access mechanisms, and to facilitate development
of device independent web applications. The World Wide Web Consortium
(W3C) [3] defines a standard known as Composite
Capabilities/Preferences Profile (CC/PP) [4]
to describe device capabilities and user preferences that can be used
to guide the adaptation of content presented to that device. JSR
188 [2] will define a set of APIs for accessing
CC/PP [4] information. This information
can be used by developers to build device independent web applications
or web content adaptation systems.
Device Independence
The W3C [3] document Device Independence
Principles [5] describes device independence
as content and applications authored, generated or adapted for a better
user experience when interacting with presentations via many different
access mechanisms. An access mechanism is a combination of hardware
(including one or more devices and network connections) and software (including
one or more user agents) that allows a user to perceive and interact with
the Web using one or more interaction modalities (sight, sound, keyboard,
voice etc.). The general phrase "device independence" is used for
this, although the access mechanisms may include a diversity of devices,
user agents, channels, modalities, formats etc.
Delivery Context
The Device Independence Principles [5]
document also defines delivery context as a set of attributes that characterizes
the capabilities of the access mechanism and the preferences of the user.
Web servers and applications that hope to achieve device independence
must be sensitive to delivery context.
Composite Capability/Preference Profiles (CC/PP) [4] has been established as the industry standard
for describing delivery context. The Open Mobile Alliance (OMA) [6] defines a standard known as User Agent Profile
(UAProf) [7] which is based on CC/PP [4] and has been embraced by the WAP community including
gateway vendors and handset manufacturers who have embedded UAProf [7] into their products.
JSR 188
JSR 188 [2] will provide the Java community
with a standard set of APIs for accessing delivery context information
that is compatible with the vast majority of web access mechanisms that
participate in delivery context negotiation. This will allow Java developers
to write device independent code that can deliver content to a multitude
of web access mechanisms while reducing development costs, and will help
to avoid a proliferation of proprietary and potentially incompatible implementations.
Web servers and applications will be able to use this API to optimally
adapt content for individual access mechanisms. J2EETM Client
Provisioning servers will be able to use this API to help determine the
appropriate client application to provision. Portal servers will be able
to use this API to adapt content and pass on delivery context information
to portlets that would adapt their behavior accordingly.
Every device independent application will need access to delivery context
information. One of the goals of JSR 188 [2] is to make this as easy as possible for the application
developer. The complexities of the transfer, representation, and resolution
of delivery context information is hidden from developers. They can
depend on any JSR 188 [2] compliant implementation
to provide requested profile attribute values in a convenient and standard
way. Use of the JSR 188 [2] API will eventually
become the preferred authoring technique for developing Java code for device
independent web applications.
JSR 188 [2] is currently in the early stages
of the JCP [1]. The expert group is collecting
requirements and refining the scope of the specification and API. The
expert group is very interested in considering current Java related authoring
techniques to ensure that the API meets the needs of developers writing device
independent Java code.
References
[1] JCP: "The Java Community Process(SM) Program", http://www.jcp.org/
[2] JCP: "JSR 188 CC/PP Processing", http://www.jcp.org/jsr/detail/188.jsp
[3] W3C: "The World Wide Web Consortium", http://www.w3.org/
[4] W3C: "Composite Capabilities/Preferences Profile Working Group",
http://www.w3.org/Mobile/CCPP/
[5] W3C: "Device Independence Principles", http://www.w3.org/TR/2001/WD-di-princ-20010918/
[6] OMA: "Open Mobile Alliance", http://www.openmobilealliance.org/
[7] OMA: "User Agent Profile (UAProf)",
http://www1.wapforum.org/tech/documents/WAP-248-UAProf-20011020-a.pdf