Scope of Mobile Web Best Practices

W3C Working Draft 1 September 2005

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Phil Archer, ICRA
Ed Mitukiewicz, France Telecom


Web access from mobile devices suffers from problems that make the Web unattractive for most mobile users. W3C's Mobile Web Initiative (MWI ) proposes to address these issues through a concerted effort of key players in the mobile value chain, including authoring tool vendors, content providers, handset manufacturers, browser vendors and mobile operators.

To help frame the development of "best practices" for the mobile Web this document - created by the members of the Mobile Web Initiative Best Practices Working Group (BPWG) as an elaboration of its charter - identifies the nature of problems to be solved, outlines the scope of work to be undertaken and specifies the assumptions regarding the target audience and the anticipated deliverables.

Status of this Document

This section describes the status of this document at the time of its publication. Other documents may supersede this document. A list of current W3C publications and the latest revision of this technical report can be found in the W3C technical reports index at http://www.w3.org/TR/.

This is the first public Working Draft of the scope document for the mobile Web Best Practices published by the Mobile Web Best Practices Working Group for review by interested parties. Publication as a Working Draft does not imply endorsement by the W3C Membership. This is a draft document and may be updated, replaced or obsoleted by other documents at any time. It is inappropriate to cite this document as other than work in progress.

This document has been produced as part of the W3C Mobile Web Initiative, following the procedures set out for the W3C Process.

With this publication, the Working Group is seeking feedback on its general approach, especially regarding the open issues identified in this document. Please send comments to the public mailing list (public-bpwg@w3.org), an archived mailing list dedicated to discussion associated with the Best Practice Working Group. See W3C mailing list and archive usage guidelines.

As of this publication, the Working Group does not expect this document to become a W3C Recommendation, and therefore it has no associated W3C Patent Policy licensing obligations. If this expectation changes, the Working Group will have an opportunity to fulfill the associated patent policy requirements with respect to a future draft.

Table of Contents

1. Introduction

As a result of widespread use of World Wide Web technologies over the Internet, a variety of content and services are now easily accessible from desktop and notebook computing platforms. Web technologies have the potential to play the same role for Internet access from mobile devices. However, today, mobile Web access suffers from problems that make the Web unattractive to use for most mobile subscribers.

The intent of the W3C Mobile Web Initiative is to make Web access from a mobile device as simple, easy and convenient as Web access from a desktop device and facilitate advancement towards the ultimate goal of "one web". In many respects the mobile web provides a new medium with new and exciting possibilities. It is in the interests of all the mobile value chain participants, from content author to end user, to minimize the impact of any fixed vs. mobile differences and maximize the benefits of all the similarities.

The mission of the Mobile Web Initiative Best Practices Working Group (BPWG) is to enable the reach of the Web to be easily extended onto mobile devices. The BPWG intends to specify and publish a set of technical best practices and develop a "mobileOK" trustmark for Web sites that support such practices and provide an appropriate user experience on mobile devices. The BPWG best practice guidelines - along with related testability checklists, where appropriate - should improve the delivery and display of content to mobile and other portable small-screen devices.

This document establishes the framework for the Best Practices guidelines, as an elaboration of the scope presented within the scope of the BPWG Charter.

The BPWG does not intend to force content authors to limit the scope of their content delivery only to those mechanisms which are currently available on mobile devices. Rather, the guidelines produced are meant to enable content to be displayed as correctly as possible on a range of devices - either directly or, if and where necessary, assisted by some server, client or third-party adaptation mechanism which is transparent to the end user.

The BPWG does not intend to develop new technology, such as markup languages. However if, during its work, the need for new technologies is identified, the group may raise requirements with other W3C groups or groups within other standards organizations.

2. Best Practice Dimensions and Scope

As the Mobile Web Initiative is primarily concerned with accessing content that would normally be rendered in a browser, the BPWG will focus initially on best practices that are most pertinent to "traditional" browsing. However, in the future phases the BPWG may broaden the scope of its work in order to take into account other content presentation options that may be available on mobile devices - e.g., using the emerging multimodal technologies.

Also, whilst many mobile applications - such as Multimedia Messaging (MMS), ringtones or podcasting - remain beyond the scope of the Mobile Web Initiative scope, the BPWG should take account of the underlying service or device features, as mobile users are not likely to differentiate between similar types of content and services.

The exact requirements for best practices - including the in-scope and out-of-scope specifics and the types of guidelines applicable to different target audiences will be addressed in detail in the BPWG recommendations, drawing, in particular, on a review of the applicable experiences from the W3C Web Accessibility Initiative (WAI).

3. Assumptions

3.1 Mobile User Experience Considerations

Most of the fixed vs. mobile user experience differences stem from

An example of content issues involved is a large bitmap which contains a sports photo. The bitmap may be unsuitable for use on a mobile device and it would need to be resized or cropped, while maintaining the relevant information, such as the position of the ball.

Examples of device and access network capabilities that need to be considered because of possible technical, ergonomic or economic implications for a mobile user include:

Wireless access offers often lower bandwidth than a fixed connection
Battery capacity is very constrained in mobile devices - certain activities tend to increase power consumption and shorten battery life
Predominantly proprietary platforms from multiple vendors - based on highly integrated hardware and relatively differentiated software (e.g., operating systems) - increase capability divergences between mobile devices. Consequently, alignment of browsing capabilities becomes quite difficult, especially when transcending the existing Open Mobile Alliance (OMA) Browsing baselines.
Cellular network connectivity is commonly charged per data volume
Mobile device input capabilities tend to differ, but are usually more constrained than in desktop terminals - four-way navigation and softkeys are most common, but touchscreen-, stylus- and keyboard-based capabilities are improving. While many mobile devices offer predictive text input, data input tends to be relatively slow and cumbersome. Many mobile devices also do not offer as wide a character repertoire as desktop devices.
Significantly less working memory and storage is available on mobile devices than in desktop terminals
processing power
Significantly less processing power is available on mobile devices than in desktop terminals - hence stringent efficiency and optimization requirements that often lead to highly integrated and differentiated solutions
Small screen is a major constraint for mobile devices - screen width, height, resolution, aspect ratio, color characteristics and performance under adverse viewing conditions (e.g., in sunlight) tend to vary and introduce additional content presentation and navigation complexities. Also, as currently only a few mobile devices are capable of multi-tasking, screen is typically "owned" by one application at a time and the user interface does not support multiple windows that are common on a desktop.
Text input tends to be very slow and cumbersome on a mobile device
voice and multimodality
Voice and multimodal technologies might supplement or enhance mobile device input and output capabilities, but currently multimodality is not commonly supported and should be viewed as an emerging technology.
Given highly differentiated capabilities and constraints of various mobile devices, making the user interface reasonably standardized, simple and efficient remains the main challenge.

Similarly, illustrative context characteristics that need to be considered because of possible usage implications include:

partial attention
Mobile devices are often used in situations when the users are unable to give their full attention to the content. A user will typically be distracted within a few seconds. If there is no activity on their mobile browser for longer than that seconds, they will be lost as a user. They will often be easily distracted from what happens to be displayed at a time on their screens. Information must be concise and easily accessible.
social situation or physical environment
In direct contrast to a desktop user typically sitting alone at a desk in the office or at home, a mobile user might often be in a number of very different situations and environments - e.g., indoor or outdoor, at a party, in a meeting, on a beach, on a train etc.
The connection between a mobile device and the internet may involve a public mobile network. Such connection may drop out from time to time as the user moves into a poor reception area. Connections may also involve non-cellular networks and other wireless technologies - e.g., Wi-Fi, Bluetooth, etc.
There are already many more mobile phones in the world than there are desktop computers and increasingly these devices are equipped with Web browsing capabilities. The phone may be the only way of accessing the Web that is available to some people, who may have no experience of accessing the Web using a desktop computer.

In the light of the above examples, assumptions made by content authors about mobile users, their devices and usage contexts may have to reflect some awareness of possible constraints and their technical, ergonomic, economic and environmental implications.

3.2 "One Web"

The social value of the Web is that it enables human communication, commerce, and opportunities to share knowledge. One of W3C's primary goals is to make these benefits available to all people, whatever their hardware, software, network infrastructure, native language, culture, geographical location, or physical or mental ability.

-from About the World Wide Web Consortium [W3C]

The number and nature of devices through which the Web may be accessed continues to grow. At one extreme, web content may be displayed on enormous plasma screens in public places with stadium-filling sound systems. However, the Mobile Web Initiative is primarily concerned with the opposite end of the spectrum — small, mobile devices. Given their proliferation and increasing diversity, making any general assumptions about specific device capabilities and/or particular circumstances of their use are, at best, unwise.

It is often in the commercial interests of content providers to maximize the reach of their materials. It is axiomatic therefore that all web resources should be equally accessible, in that they should be made available using standard communication and formatting mechanisms. It is good practice to create user experiences that do not depend upon the particular implementation of standards or the end-user's choice of a particular browser.

That said, it is legitimate for content providers to target particular classes of user or to provide material and services that are tailored to particular situations. What is appropriate and desirable in one environment might be inappropriate or impractical in another.

This leads us to characterize "One Web" by postulating that:

3.3 Adaptation Layer

Due to increasing diversity of terminal devices the BPWG's working assumption is that multiple versions of content representation or adaptation of content to a particular set of device capabilities will be commonly used for the foreseeable future. For example, adherence to XHTML-MP can lead to different results on different devices running the same browser software. The context in which a web resource is to be displayed must therefore be addressed and hence the concept of an "adaptation layer".

As discussed above, "One Web" does not mean that precisely the same information must always be available in precisely the same way from a given URI. The context in which a web resource is to be displayed must therefore be addressed — hence the concept of an "adaptation layer" becomes an integral, if transparent, element of the web.

In order for the adaptation layer to do its job, content must be created in a way that makes adaptation relatively simple and, critically, makes the results predictable.

The BPWG will therefore strive to develop Best Practice Guidelines that will:

3.4 "mobileOK" Trustmark

Development of a "mobileOK" trustmark is a key objective of the Mobile Web Initiative. The intention is to establish a set of validation tests to which content resources can be subjected. If passed - possibly subject to some content adaptation - a particular resource will be deemed to be mobileOK. This information will be presented in a visual form by means of a logo and in a machine processable form - e.g., for use by content aggregators.

The development of a "mobileOK" trustmark implies two work areas for the BPWG: defining the criteria a resource must meet to be mobileOK - based on the best practice guidelines - and defining the process and platform through which the trustmark is to be delivered.

Given the necessity of an adaptation layer in certain circumstances and the plethora of conflicting demands made by the "real world", the BPWG will have to define the interdependencies between the Best Practice Guidelines and the "mobileOK" trustmark. The two need to be coupled in some way, but the exact details remain to be specified.

The "mobileOK" trustmark is intended not only to help authors to create content that will render correctly on mobile devices, but also encourage software manufacturers to develop a range of compatible tools, including authoring tools and clients. The "mobileOK" trustmark is envisaged to have relevance across the entire content production chain.

3.5 "mobileOK" Conformance and Best Practices

Levels of "mobileOK" conformance in relation to different dimensions of the specified best practices - as applicable in certain target contexts - will be addressed in detail by the Best Practice Recommendations.

For example, different sets "mobileOK" conformance requirements could be applicable to different categories of browsers - e.g., "full" browsers, WAP browsers, voice browsers, etc

Also, specifications of "mobileOK" conformance criteria could be based on the "state of the art" practices prevailing at a particular point in time - e.g., MobileOK2005, MobileOK2007, etc.

Another option could be to specify some "backward compatible" levels of "mobileOK" conformance criteria - e.g., MobileOK, MobileGood, MobileExcellent - based on meeting a number of increasingly stringent best practices or their subsets or supersets.

Another option would be to consider different content profiles - e.g., MobileOK HTML/CSS/PNG or MobileOK XHTML/CSS/SVG/ECMAscript - or some similar compound document profile variations.

As some of these options are not mutually exclusive in nature, certain combinations of "mobileOK" conformance criteria could also be considered.

3.6 Open Issues

The BPWG anticipates that it will be necessary to structure the work on the Best Practice Recommendations into two or more phases, with the initial focus on best practices that are most pertinent to "traditional" browsing. However, no specific decisions have been taken yet by the group with regards to which particular issues might be deferred to Phase 2 in the interest of accelerating the completion of the Phase 1 work. The exact scope of work in these two phases remains an open issue.

4. "mobileOK" Validation and Delivery Requirements

The exact requirements for the methods and platforms for "mobileOK" validation as well as types of the underlying validation criteria will be addressed in detail by the Best Practice Recommendations.

5. Internal and External Liaisons

The principles developed by the W3C Device Independence Working Group (DIWG) are recognized as being highly relevant to the Mobile Web Initiative. In particular concepts such as authoring units, delivery units and display units are important. The BPWG may have to extend this into a broader conceptual architecture. It is anticipated, for instance, that the group's best practice guidelines will include conditional statements in the form "if feature X is supported by the target device then a delivery unit must/should be used in this way (else in some other way)."

The BPWG will try to coordinate their work with the related efforts within the W3C, including:

The BPWG will also try to establish working relationships - based on formal liaisons, if and where appropriate - with certain organizations outside of the W3C, whose activities might impact the Mobile Web Initiative and/or be influenced by it, including:

6. Resources

The BPWG recognizes the existence of many resources that represent a considerable amount of work already done in this area - for example, the Web Accessibility Initiative (WAI) guidelines and content authoring guidelines from various companies such as [Opera].

The Mobile Web Initiative homepage provides links to several of these resources and more would be added in the near future.

7. References

"Making Small Devices Look Great - Opera Authoring Guide for Devices ", see: http://my.opera.com/community/dev/device/
" About the World Wide Web Consortium", see: http://www.w3.org/Consortium/about-w3c.html#universal-access1

8. Acknowledgements

The editors would like to recognize the contributions of the following members of the W3C Mobile Web Initiative Best Practices Working Group (listed in alphabetical order):