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DVB-HTML a new standard? Part 2

Posted on July 14, 2002

in Code

by Mark Bolton (mark_bolton)

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Mark Bolton

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User since: March 07, 2002

Last login: September 17, 2007

Articles written: 3

Continuing from Part 1, we start to look in further detail at the Standard and its effect on web development.

Document Type Definition and XML Namespace Requirements

As the DVB-HTML specification requires content to be validated against a specific DTD then any content to be displayed will have to provide the doctype declaration at the head of the document. This doctype is shown below:

<! DOCTYPE html PUBLIC "-// DVB//DTD XHTML DVB-HTML 1.0//EN" 
"http://www.dvb.org/mhp/dvb/dvbhtml-1-0.dtd">

Also as the namespace policies set down by the W3C are respected for XHTML the namespace link should also be included in the header information. Your document should now look like this:

<! DOCTYPE html PUBLIC "-// DVB//DTD XHTML DVB-HTML 1.0//EN" "http://www.dvb.org/mhp/dvb/dvbhtml-1-0.dtd"> <html xmlns="http://www.w3.org/xhtml"> <head> </head> <body> &lt/body> &lt/html&gt

DVB-HTML uses modules from the W3C XHTML Modularisation Recommendation and also adds a module to handle the specialist Intrinsic Events required for event handling.

Supported Modules

  • Structure
  • Text
  • Hypertext
  • List
  • Presentation
  • Bidirectional text
  • Forms
  • Basic Tables
  • Image
  • Client-side image map
  • Object
  • Frames
  • Target
  • Iframe
  • Meta Information
  • Scripting
  • Style Sheets
  • Style attribute
  • Link
  • Base
  • DVB Intrinsic Events (defined by DVB)

    • Un-supported Modules

  • Applet
  • Edit
  • Basic Forms
  • Tables
  • Server-side image map
  • Intrinsic events
  • Name Identification
  • Legacy

    • The only module added is the DVB intrinsic events, this has been done to include three event handlers to the body and frame elements which are:

  • dvbdomstable - ensures the DVB-HTML document has been fully received and parsed
  • load - when all parts of an embedded Object element have been received
  • unload - when the document is removed from the window or frame

    • the additional module has been produced in accordance with the XML namespace defined by the DVB. These additional events have been added so that MHP can trigger other events.

    In order to use the additional module and remove any potential conflicts with the W3C XML namespace a separate XML namespace is used by DVB-HTML and all commands are prefixed by dvbhtml:. An example of this is shown below:

    <! DOCTYPE html PUBLIC "-// DVB//DTD XHTML DVB-HTML 1.0//EN" "http://www.dvb.org/mhp/dvb/dvbhtml-1-0.dtd"> <html xmlns="http://www.w3.org/xhtml"> <head> <script type="text/ecmascript" src="scriptname.js"> </head> <body xmlns:dvbhtml="http://www.dvb.org/mhp" dvbhtml:ondvbdomstable="startevent()"> <!-- content here --> &lt/body> &lt/html&gt

    Comment

    Our browser sniffing previously described in part 1 also enabled us to identify which modules would be supported, so at this stage we are ready to produce a document or application using the DVB-HTML standard.

    In Part 3 of this series we take a look at the supported MIME media types and CSS for a DVB-MHP system.

    References

    Mark Bolton is an engineer working on the development of Hi-Definition-Television (HDTV), who also has an active interest in the development of the internet through his company Boltonmedia

    Currently based in Shanghai, China and actively developing websites in both English and Chinese whilst designing and developing new methods of viewing these websites

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    cool article, typo warning

    Submitted by skunk on July 16, 2002 - 05:18.

    This is shaping up to be an excellent series - thanks Mark! However, there's a small typo in one of the samples above.

    &lt;script type="text/ecmascript" src="scriptname.js"&gt; should be &lt;script type="text/ecmascript" src="scriptname.js" /&gt;

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    typo warning

    Submitted by mark_bolton on July 16, 2002 - 06:51.

    LOL caught me: the standards police are dammed quick around here,
     
    Funny thing is the same typo exists in the DVB-MHP specification, but there are no reader comments for that!

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