82 lines
3.4 KiB
Markdown
82 lines
3.4 KiB
Markdown
---
|
|
title: Channel Definition Format
|
|
---
|
|
|
|
The Channel Definition Format was a Microsoft file format for syndication
|
|
based on XML. It was designed for its *Active Channels* technology and got
|
|
extended for *Active Desktop* integration or for [OSD][osd].
|
|
|
|
## Specification (or lack thereof)
|
|
|
|
CDF does not have a standardized specification: [a note][w3c] was sent to the
|
|
W3C in 1997 with a very early draft of the format, with the intention of later
|
|
making it into a standard, but there were no further updates.
|
|
The [Microsoft docs][docs-970314] of that time are the same as this draft.
|
|
|
|
The [latest documentation][docs], from 2002, describes a format that varies a
|
|
lot from that W3C note.
|
|
|
|
There is no official <abbr title="Document Type Definition">DTD</abbr> or
|
|
<abbr title="XML Schema Definition">XSD</abbr>. Someone wrote a [DTD][dtd]
|
|
with support for the *Active Desktop* and [OSD][osd] extensions.
|
|
|
|
I wrote my own XSD files to help me use this format in [ITSB][itsb]:
|
|
|
|
* [W3C draft](./xsd/cdf-w3c.xsd)
|
|
* [CDF 0.4](./xsd/cdf.xsd) (latest)
|
|
|
|
The CDF 0.4 XSD includes the
|
|
[CDF Extensions for Active Desktop Items][active-desktop-ext].
|
|
|
|
## Support
|
|
|
|
CDF was supported by Internet Explorer 4 to 7, and no other software is known
|
|
to have supported this format.
|
|
|
|
The format was created and implemented in IE4 while XML was still a draft,
|
|
causing some valid XML documents to not be understood properly by IE4, and all
|
|
the sample CDF files provided with IE4 to make XML parsers scream.
|
|
|
|
Support was dropped in 2009 with the release of IE8 as it lost against RSS,
|
|
and as Microsoft's dedicated RSS team implemented RSS support in IE7.
|
|
|
|
## Notable features
|
|
|
|
* Scheduling options to avoid useless synchronizations
|
|
* Nested channels (merge multiple feeds into one)
|
|
* Custom icons in the IE favorites sidebar
|
|
* Customization of IE's crawling behavior when making a website available
|
|
offline, using `<LINK REL="OFFLINE" HREF="...cdf">`
|
|
* *Active Desktop* integration to display articles on the desktop
|
|
* Integration with [Open Software Description][osd] to send software updates
|
|
|
|
## Usage
|
|
|
|
I use this format in [ITSB][itsb] to provide separate channels generated from
|
|
each RSS feed, or channels that group channels together. This second form
|
|
usually causes Internet Explorer to lag heavily due to the few megabytes of
|
|
items it is downloading in a single file. All of those CDF files have been
|
|
tested and confirmed to be working with Internet Explorer 6 SP1 on Windows
|
|
2000 SP4.
|
|
|
|
## Links
|
|
|
|
* [March 10th 1997 specification][docs-970314]
|
|
* [March 21st 1997 specification][docs-970321]
|
|
* [Latest documentation][docs] (CDF 0.4)
|
|
* [Extensions for Active Desktop items][active-desktop-ext]
|
|
* [Unofficial DTD][dtd]
|
|
* [W3C draft][w3c]
|
|
* Special Edition Using HTML 4, [Building Channels with CDF][building],
|
|
Jerry Honeycutt
|
|
|
|
[active-desktop-ext]: https://docs.microsoft.com/en-us/previous-versions/windows/internet-explorer/ie-developer/platform-apis/aa768141%28v=vs.85%29
|
|
[building]: https://www.rigacci.org/docs/biblio/online/html4/ch30/ch30.htm
|
|
[docs]: https://docs.microsoft.com/en-us/previous-versions/windows/internet-explorer/ie-developer/platform-apis/aa768139(v=vs.85)
|
|
[docs-970314]: http://xml.coverpages.org/cdf970314.html
|
|
[docs-970321]: http://xml.coverpages.org/cdf970321.html
|
|
[dtd]: http://www2.cmp.uea.ac.uk/~jrwg/JAXP/examples/cdf/cdf.dtd
|
|
[itsb]: https://tilde.town/~lucidiot/itsb/
|
|
[osd]: ./osd.html
|
|
[w3c]: https://www.w3.org/TR/NOTE-CDFsubmit.html
|