A Framework for Web Content Adaptation
From mobile phones, PDA to WebPad or even TV, the diversity of future web access devices will continue to increase. Current methods of Web content adaptation use style sheets as separate profiles that correspond to a documents appearance. However, only text-mode document-style re-formatting is supported by either of the two current standards, the Cascading Style Sheet (CSS) and the Extensible Stylesheet Language (XSL) . As indicated in , more categories of style re-formatting are even in a stronger demand, e.g., mathematical characters with graphic-rich boxes, animated text/cartoon, graphic-rich advertisement, etc. Due to different capabilities of mobile terminals, it is even required to adapt web contents not only to different styles, but also to different modes.
2. Multi-modal Content Adaptation for Universal Access
A single-modal content reformatting is not sufficient to support the universal access of a web content. A multi-modal content adaptation represents not just the increase or decrease of display quality, e.g., font size and color. Even a text can have more than one mode of presentation, for instance, the mode of fixed text and the mode of animated text (a text with animation feature). Multi-modal content is usually easier to be identified when the content contains multimedia. For example, a video clip may contain raw data from video, audio in two or more languages, and closed text caption. Neither current W3C nor WAP standard is able to handle such content. In , a transcoding framework was proposed to adapt multimedia content into various types of terminals. In multimedia one can also think of transcoding the presentation axes of Spatial, Temporal, and Hyperlinking layout. On a large screen, images can be placed side a side, while at a small screen they may be better off in a time sequence. Scrolling is not always the optimal solution, for both the user interface and the content presentation.
Even a single text can have more than one mode of presentation. The following example illustrates a text in a multi-modal presentation.
Original content: Right Arrow
Normal text mode: Right Arrow
Animated text mode: <text>Right Arrow <animate from ="0px" to="10px" dur="1"/></text>
Pictogram mode: →
Graphic mode:Animated graphic mode:
Speech mode: <speak xml:lang="en-US"><para>Right Arrow</para></speak>
3. The Content Adaptation Framework
To support a multi-modal content adaptation, an architecture or a framework is necessary. However, it is not the purpose of this paper to propose a new architecture. Instead, we would like to address our interests on how content relates to users, i.e., the personalization. Sometimes We are using 'customization' to indicate adaptation to the machine, which is a kind of static adaptation, while 'personalization' is to the user, which is a dynamic process. In particular, our main interest on content adaptation is to ensure a proper content delivery according to
These are further explained in the following subsections.
3.1 Terminal Capability
Not all mobile terminals are made equal. Knowing a terminals capability, the content can be properly adjusted for a better presentation. This is important especially when the variation of mobile terminals is expected to be very high. One can imagine that future personal information appliances can range from basic mobile phones with a black-and-white 4-line ASCII display, to more advanced PDAs with an SVGA 4-inch color display. Next to display, there is the user feedback interface. Mouse and keyboard can be suboptimal for smallscreen and mobile devices. Speech orientation appears natural on phones.
3.2 User Characteristics/Preference
The terminal capability is not the only factor to determine the content adaptation. A users preference can also be a very important aspect. Just like a personalized Web page, the content can be customized to each user. Currently, the efforts for Web accessibility to universal users have been conducted at W3C's WAI (Web Accessibility Initiative). However, it requires other optimizations such as the transcoding of a content to meet a user's preference or capability.
3.3 User Location/Context
Due to the terminal mobility, it is also good to consider content adaptation based on the user location and/or context. For example, a user in a meeting may switch his handset from the speech mode to visual mode, in favor of silent content delivery. Technically, this can be handled at the composition layer using SMIL.
4. The Issues
We are interested in the following issues regarding content adaptation frameworks and would like to discuss them in this workshop.
Location of the transcoding engine: To adapt contents to a variety of devices, a transcoding engine or a reformulation mechanism is needed before the contents are delivered to the users. Is there an optimal way to locate such engine ? For example, this engine can reside together with the content server, the browser (the client), or some machine (gateway) in between the two ?
Content categorization: Some contents are sometimes not suitable or unpreferred to be reformatted or reformulated, while some others are created just for adaptation among a subset of devices. Is there a way to categorize the contents such that the automatic content adaptation/reformating can be optimized ? For example, the adaptability level can be defined such that users know how much distortion the reformatted content is from the original version. A rough idea is as follows. Level 0 represents that a content is universal and can be trans-formulated to adapt to any device without losing the original meaning of the content. Level 1 can be defined as a content that is created with the knowledge of device capability. And level 2 can represent a content that is created with detailed knowledge of some subset of devices. ... et al.
Accessibility guidelines: Can tools be implemented to aid/enforce those guidelines? It will be impossible to stop authors for abusing markups and being poor authors, e.g. poor document structure, poor alternate text information for images, etc. Therefore, accessibility guidelines will be critical even with advanced technologies and not necessary to be a short term solution. However, we need device-independent guideline as well as device-depedent guideline. The first one deals with document semantics and the second with the syntax and presentation.
Market concern: most content developers are market-sensitive. basically, they will just focus on a small number of devices which take the most market shares and ignore the rest. the complexity and cost involved in adaptation across different devices must justify the effort.
Cost and layout control: Adaptation results might not be optimal to certain device. however, most of the content providers want the best presentation they can get and therefore, like to have strong control on the final presentation. will this be a dilemma ?
Todays Web technology is not sufficient for multi-modal content adaptation, although some of the issues can be solved or being taken care of. For example, there are issues on the need for interoperability to various terminal/user profiles, and the adaptation to layout a content with different presentation axes of Spatial, Temporal, and Hyperlinking. It is up to future discussions in related working groups whether we need a new standard or to make use of current methods and enhance them. However, as indicated in , the Webs continuing development brings more incompatibility problems to the browser. When achieving a multi-modal scenario, it is worth to spend a little effort such that the above mentioned problems are minimized.