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Channel Definition Format (CDF) was a Microsoft-proposed XML specification for describing frequently updated collections of web content. A CDF file organized a publisher’s channel into items and optional subchannels so compatible client software could display the collection and retrieve updates on a schedule. Microsoft submitted the proposal to the W3C in 1997; it was a proposal for consideration, not a W3C Recommendation.
What did Channel Definition Format describe?
CDF described a publisher’s content collection as a channel. A channel could contain items—often references to web pages—and could also contain nested channels. The specification envisioned a user selecting a channel in compatible software, which would use the downloaded CDF file as a local index and retrieve channel content according to a schedule. The publisher could serve the file from an ordinary HTTP-capable web server.
In other words, CDF described how to organize and point to channel content; the file was not itself necessarily the content being delivered. The 1997 specification describes automatic delivery by compatible receiver programs, not a guarantee that every client could interpret or act on a CDF file.
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What information could a CDF file contain?
The proposal used XML and supplied a DTD defining its elements and attributes. Its vocabulary included fields for describing channels and their contents, as well as schedule and presentation information.
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| CDF element or field | Purpose in the proposal |
|---|---|
| Channel | A named collection that could contain items and subchannels. |
| Item | A unit of channel information, commonly associated with a web page through a URI and descriptive metadata. |
| Schedule and UserSchedule | Represented schedule information and references to schedules specified by a client or user. |
| Logo | Provided imagery representing a channel or item. |
| CategoryDef | Defined categories, with the option of child categories. |
| Descriptive metadata | Could include a title, abstract, author, publisher, publication date, keywords, category, and rating. |
| Other channel data | Could include a URI for an introductory page and a minimum-storage value; the vocabulary also included tracking parameters. |
These are capabilities described in the historical proposal, not a description of current web-feed conventions.
What is the history and standards status of CDF?
The W3C submission registry records Microsoft’s CDF submission on March 9, 1997. The specification is dated March 10, 1997, and names Castedo Ellerman of Microsoft as its author. The submission asked the W3C to consider the specification and proposed that the Consortium work on it and ultimately adopt it as a Recommendation. That request documents a proposed path, not adoption: CDF should be described as a Microsoft proposal submitted to the W3C, not as a W3C Recommendation.
The W3C-hosted specification calls CDF “an open specification” for publishers to offer frequently updated collections from a web server to compatible receiver programs. That is the proposal’s own description in its 1997 context, not a current W3C endorsement. Read the CDF specification hosted by the W3C and the W3C submission record.
What does “CDF file” mean in this context?
In this topic, a CDF file is a file written in the proposed Channel Definition Format: an XML description a compatible client could use as an index for a channel’s structure and content references. The term alone does not establish that a file is a current feed, that a modern application supports it, or that the format became a W3C standard.
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