W3C WIDGETS

A Solution for Implementing Platform-independent Mobile Applications

Stefan Schäfer, Stefan Christmann

Application Systems and e-Business, University of Göttingen, Platz der Göttinger Sieben 5, Göttingen, Germany

Svenja Hagenhoff

Institute of Media Management, University of Applied Sciences St. Poelten, St. Poelten, Austria

Keywords: Widget, Mobile application, Platform-independency.

Abstract: The mobile internet is very heterogeneous at all levels - this is true for end devices as well as for operating

systems and runtime environments of mobile applications. Therefore all software providers face the

challenge of developing platform-independent applications and making them usable on a maximum number

of end devices. One possible way of doing this is provided by Widgets - small software programs with a

limited functional scope that are executed by a Widget-engine. This article looks at the state of development

of the most important W3C Widget-standards and analyses their prospects of success.

1 INTRODUCTION

The mobile internet poses great challenges for

software providers as well as for customers, because

it is a strongly fragmented market with a multitude

of different producers of end devices and platforms

for the production and supply of software (Gartner,

2010; Admob, 2010, p.6). Customers who change to

a new device often find it difficult or even

impossible to use their former applications on the

new end device and to transfer their data. This is

also a problem for the producers of software, as they

have to provide a great variety of software for

different platforms in order to retain customers. This

leads to a high demand on development resources

and subsequently to increased software production

costs.

Solutions for this are projects like PhoneGAP or

Appcelerator, which translate web applications

written in (X)HTML, CSS and JavaScript into native

applications for mobile devices (PhoneGap, 2010).

J2ME Polish – as an alternative – is an open source

extension for Java Micro Edition (JavaME) which

makes it possible to design the user interface of

JavaME-based applications through CSS. It also

includes a database of devices providing an easy

way for developers to adapt applications to several

hundreds of mobile phone types (Müller & Reiprich,

2008, p.2). Both products are mainly solutions for

the existing variety of different platforms. W3C, on

the other hand, tries to counterbalance the great

variety of software development solutions by its

Widget-standard and to find platform-independent

solutions for applications with a low functional

scope in order to access a maximum number of end

users.

Jaokar and Fish (2006, p.99) define a Widget as

a "downloadable, interactive software object that

provides a single service such as a map, news feed

etc". "Widget" is an artificial word combining

window and gadget. This goes back to the use of

Widgets in the MIT Athena Project, where a window

was associated with an object and called Widget

(McCormack, et al., 1989, p.4). The W3C defines

Widgets as applications executed on the client side,

but developed using web standards. Widgets are

usually downloaded and installed on an end device

where they run as independent applications. They

may also be integrated into web sites and accessed

through a web browser (Cáceres & Priestley, 2009).

Therefore, a great variety of runtime environments is

available. According to the W3C definition of

Widgets they may be called mobile applications if

they are executed independently on a mobile end

device or in a web browser. Such a runtime

environment is called a Widget-engine. It is software

that can execute small applications (Widgets) in

115

Schäfer S., Christmann S. and Hagenhoff S..

W3C WIDGETS - A Solution for Implementing Platform-independent Mobile Applications.

DOI: 10.5220/0003196101150118

In Proceedings of the 7th International Conference on Web Information Systems and Technologies (WEBIST-2011), pages 115-118

ISBN: 978-989-8425-51-5

 2011 SCITEPRESS (Science and Technology Publications, Lda.)

their context and present them to the user (Sachse,

2010, p.7).

2 W3C WIDGET-STANDARD

In August 2006 W3C published a document called

Web Applications Packaging Format Requirements,

defining the requirements towards a uniform

packaging format for web applications (Cáceres,

2006a). This working group further specified the

requirements, leading to the final requirement

document Widgets 1.0 Requirements. Also the

elements for the execution of Widgets were

identified (cf. Figure 1).

Technologies such as XMLHttpRequest or

ECMAScript (also called JavaScript) are well-

established and need no further standardization in

the process of Widget-specifications. However, the

packaging format for Widgets, a uniform MIME-

type (media type), content and construction of the

configuration document, and an API for Widgets

need to be standardized. This Widget-API does not

aim at providing access for device-specific

functions, but only access to the Widget and its meta

data. Over time, different working groups were

established for the development of device-specific

functions.

In 2008 the Web Application Formats Working

Group of W3C was merged with the Web API

Working Group to form the Web Applications

Working Group. Its task is to further develop the

specifications on APIs and Widgets. This working

group has developed the following specifications on

Widgets, which can be regarded as the main content

of the standard (W3C, 2010).

Widget Packaging and Configuration (P&C):

This specification stipulates, among other things, the

structure of configuration files, the packaging, the

inner structure and the possibilities for the

internationalization of Widgets.

The Widget Interface (TWI): An API that

facilitates the access to metadata of the Widget such

as author or name in a simple way and provides a

DOM-method to access URLs within Widgets.

Widget Access Request Policy (WARP): WARP is

a safety model that regulates the access to network

resources through settings of the configuration file

and through providing methods that provide a wider

access of Widgets to network resources.

Digital Signatures for Widgets: This specification

describes how Widget packages may be digitally

signed using XML signature syntax in order to

guarantee the reliability of the Widget's source.

Widget URIs: This specifies the addresses through

which resources within Widgets may be identified

and accessed.

View Mode Media Feature: This Feature describes

how Widgets behave in certain views. As Widgets

are executed on a great variety of end devices, the

space available on the screen varies greatly. On the

other hand, they may be executed for example as

full-screen applications but also as minimized

applications taking only a small part of the screen.

Widget Updates: This specification describes the

update mechanism that is needed in order to

distribute new versions of Widgets to users.

3 IMPLEMENTATION AND USE

When the requirements towards a Widget-standard

were stipulated, the existing Widget-landscape was

analyzed and a multitude of Widget-platforms was

identified (Cáceres, 2008). The existing implementa-

tions are described in the following chapter.

Figure 1: Required elements for running Widgets (cf. Cáceres 2008).

Packaging,

Distribution,

Deployment

Meta data,

Configuration

Scripting,

Network

Access

User Interface,

Accessibility

Presentation,

Behavior

Packing Format &

Digital Signature

Media Typ

XML

Configuration

Document

DOM

HTTP + URI + Unicode

ECMAScript

XMLHttpRequest Widgets API

CSS

Resources

(images, sounds, etc.)

(X)HTML or proprietary XML

Widget User Agent

Widget

Resource

Instantiated

Widget

light blue areas require standardization

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3.1 Implementations

Currently, implementation experiences are gathered

for the Widget specifications P&C, TWI and

WARP. For each implementation there is a number

of test cases and an implementation report (Cáceres,

et al., 2010). BONDI's Widget-engine was the first

to fulfill all test cases of the Widget-standard 100%.

Aplix Web Runtime and the Wookie-Project of

Apache were the next to fulfill the standard 100%

(W3C, 2009). Moreover, there are other

implementations with expanded functionalities.

Table 1 gives an overview.

BONDI is an initiative started by Open Mobile

Terminal Platform (OMTP) in 2008. OMTP is a

forum created by network providers with a total of

38 participants from phone producers to chip

providers and software/operating systems developers

(OMTP, 2010). BONDI is not an acronym but is

named after the Bondi Beach in Sydney. In addition

to implementing the Widget standard, BONDI

provides new interfaces to access the functions of

mobile phones. These are functions such as

localization, start of programs and access to the

address book in a secure manner. The platforms

currently supported include Windows Mobile,

Android, BREW, iOS, WebOS, BlackBerryOS and

Symbian. BONDI belongs to the mobile sector.

Aplix Web Runtime is a runtime environment for

Widgets for the systems Android (Google) and

Maemo (Nokia). It supports the JavaScript-APIs by

BONDI and JIL (Judge, 2010). Aplix Web Runtime

also belongs to the mobile sector.

Wookie is a server application providing an

opportunity to upload and provide Widgets. The

Wookie-project was supported by the IST-program

of the European Union as a part of the

TENCompetence project and was exclusively

developed by developers from the University of

Bolton. The Wookie-server is an application

developed in Java with a Widget-engine and other

plug-ins that can integrate Widgets into web

applications such as Wordpress or the course

management system Moodle (Wilson, et al., 2009).

Wookie is an implementation for web applications

that facilitates the embedding of Widgets into web

sites.

3.2 Dissemination and Acceptance

When the first document with requirements towards

Widgets was published, it triggered very mixed

reactions. They ranged from enthusiasm about the

possibility to write a single application and use it on

several platforms to doubts whether platform-

independent standards would be acceptable to total

rejection. In general, however, the first attempt at

overcoming the fragmentation in Widget-

development was favourably received (Cáceres,

2006b). Many of the important platforms for mobile

end devices appreciate and support the Widget-

standard, as shown by a great number of

implementations. However, there are not yet any

implementations for Apple devices. Besides the

Aplix Web Runtime, there is no other

implementation for the Android-platform. Very

probably, Aplix Web Runtime will not be available

as open source, but will be licensed to network

providers (Wilson, 2010). Provided a wider

acceptance and distribution of the Widget-standard,

Apple and Google may well yield to the public

pressure and develop more Widget-engines

implementing the W3C standard for Apple as well

as for Android platforms.

4 CONCLUSIONS

The clear advantage of W3C Widgets is that they are

platform-independent and therefore universally

applicable. They can be used as small desktop

applications, as mini-applications integrated into

web sites or as part of a Widget-engine running on

mobile end devices. Meanwhile, developers from

Table 1: Available Implementations of W3C Widget Standard.

Implementation Implementation of

standard

Area Runtime Environment

BONDI 100% compatible Mobile E.g. Windows Mobile, Android, BREW, iOS, webOS,

BlackberryOS.

Applix Web Runtime 100% compatible Mobile Android, Maemo.

Wookie 100% compatible Web Java-based operating systems,

web browsers.

Palette-Portal divergent/extended Web Web browsers; integrated into learning portal.

Opera divergent/extended Mobile

& Web

Stationary operating systems with Opera browser

starting from version 9.0, Windows Mobile, S60.

W3C WIDGETS - A Solution for Implementing Platform-independent Mobile Applications

117

many areas and companies are involved in the

development of the standard. One of the great

disadvantages of the Widget-standard is the lack of

device APIs. The Device APIs and Policy Working

Group is working on a specification, but there have

been no tangible results yet. Although Widgets are

supposed to be mini-applications with just a small

scope of functions, they have the disadvantage of not

including any code that is executable on the server

side and can therefore not generate dynamic content

without using JavaScript. This disadvantage can be

compensated partly by providing JavaScript within

the Widget-engine.

The implementation and use of the W3C

Widget-standard by major companies and consortia

is of vital importance for its success. Furthermore, a

generally accepted specification of device APIs is an

indispensable condition for the harmonization of

mobile applications. The markets for mobile

operating systems and browsers currently undergo

diverging developments. While in the area of

browsers, systems based on the rendering engine

WebKit develop into the dominant platform and

fragmentation is decreasing, in the area of operating

systems the publishing of a growing number of new

systems leads to more and more fragmentation in

this area. The lower level of fragmentation in the

browser area could promote a development trend

competing with W3C Widgets: the use of web

browsers as runtime environment. The new standard

HTML5 makes it possible to continue using web

applications offline using local SQL databases

(W3C, 2008). The future of the W3C Widget-

standard remains open. If it is consistently

developed and supported by the producers of

operating systems, it may become a runtime

environment for mobile applications to be reckoned

with.

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