Introduction to Document Type Supported by Mobile Devices
A key device characteristic is the set of supported document types. A number of different file types are supported by various mobile devices. This section provides a brief overview of these document types and some of the features and history associated with each.
HDML was originally developed by Unwired Planet which later became Phone.com and then Openwave. The only real deployment of HDML was in Japan on KDDI's Tu-ka and au. HDML consisted mainly of basic text and links and was optimized for devices with very low processing capabilities. Later OpenWave joined with Nokia and other mobile manufacturers to form a standardisation body the WAP (Wireless Application Protocol) Forum where HDML was recast and evolved into WML.
Was an interim format on the development of WML - perhaps as few as 1 or 2 phones only ever implemented support for this document type.
Was the principle document format supported by the first generation of mobile internet phones in the rest of the world except for Japan. Key features of the WML format included:
- Card/deck metaphor
- XML based
- Associated binary compressed format WBXML for optimization of bandwidth
- Abstract user control elements (the "do" element)
Unfortunately initial implementation were buggy and in reality the abstract user control elements proved too flexible meaning a content author was unable to guarantee a consistent user experience across different devices because handsets differed substantially in their implementation
WML 1.1 was still very simple in terms of the user experience it allowed. WML 1.2 added more user control elements allowing for a richer user experience.
cHTML(compact HTML) was developed by DoCoMo and is based on a subset of elements from HTML 3.2 with a few additional attributes/elements (MARQUEE, BLINK, accesskey) and emoji (a set of characters displayed as pictograms/small icons to efficiently represent commonly used images e.g. sports/weather symbols.) Subsequent versions of cHTML were refered to as i-Mode HTML (this was sometimes abbreviated to iHTML.)
HTML is the lingua franca of the World Wide Web and was invented around 1990 by Tim Berners Lee. As mobile devices became more sophicated and powerful gradually more and more User Agents have attempted to permit access to the whole of the web by attempting as full an implementation of HTML as possible. Although these implementations have become increasingly sophisticated over time, never the less, reduced device capabilities still limit the user experience one is able to achieve on such browsers.
XHTML 1.1 Basic/ XHTML MP 1.1/ XHTML MP 1.2
XHTML is the next generation of HTML and is a hybrid between HTML and XML. XHTML Basic is a subset of XHTML intended for limited capability devices such as mobile phones. XHTML MP is an extention to XHTML Basic specified by the successor to the WAP forum, the Open Mobile Alliance (OMA), with some mobile specific additions. Since XHTML MP is a superset of XHTML Basic - any device that supports XHTML MP therefore also supports XHTML Basic. In practice XHTML Basic only implementation are relatively rare with XHTML MP achieving broad support from handset manufacturers. Currently the W3C plans to harmonize XHTML Basic with XHTML MP (i.e. it is planned to extend XHTML Basic to include the additional features of XHTML MP)
XHTML Others (Strict/Transitional/Frameset)
These represent the "full" versions of XHTML. As described above in the HTML section these formats may be supported by devices attempting to permit access to as much of the whole web as possible.
This chart illustrates the evolution of the various markup languages for mobile devices.