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DVB-HTML


Notes:


DVB-HTML is a XHTML implementation using European characters and the Document Type Description (DTD) at "http://www.dvb.org/mhp/dtd/dvbhtml-1-0.dtd". Web browsers traditionally attempt to display web pages which do not fully conform to HTML standards, by ignoring unsupported features. MHP attempts to formalize this behaviour with rules to support "Invalid but conformant documents". However, the application of these rules is unclear to this author. DVB-HTML uses XHTML modules: Structure, Text, Hypertext, List, Presentation, Bi-directional Text, Forms, Basic Tables, Image, Client side Image map, Object, Frames, Target, Iframe, DVB Intrinsic events, Metainformation Module, Scripting, Style sheet, Style Attribute, Link and Base Omitted: Applet, Edit, Basic Forms, Server side image map, Intrinsic events, Name Identification and Legacy. The strict use of XHTML would limit the use of some legacy HTML features. One explicitly mentioned in the standard is that the id attribute has replaced the name attribute in specifying a target frame. The result could be that links to target frames will not work, if they use the name attribute. The alternate text for disabled users is supported. An obvious way to implement this would be with text displayed over, or in place of an image. A talking browser could read text to a blind user, but the details are implementation dependent. The accesskey attribute of HTML 4 is implemented. This could be important to TV devices as it allows hypertext to be navigated with a few keys on a TV remote control. Implementations are not required to provide a scrolling mechanism for frames. However it is likely any practical implementation will need to do so. A major limitation of the MHP standard is that it does not define referencing of video segments of finite duration. MHP is not a true multimedia format, in the style of the Synchronized Multimedia Integration Language (SMIL). It provides triggers (discussed below) for synchronization.