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Appcast Brainstorming

The purpose of this page is to capture software updates practices in the wild, as one effort to codify practices currently used in the automatic update system called Sparkle.




Sites like,, and among others should be investigated and documented for object names and attributes.

Among common data in a software update changelog are changes or fixes, completed bugs, new features or modified behavior, and known issues. A version number is also typically supplied, but takes on many forms and is not always numeric.

Lastly, this work should be seen as compatible with hAtom, possibly as a prelude to a format that could be embedded as the payload of an hfeed object.

Work should be carried out on the Appcast Examples page.

Related Work

Sparkle-specific Appcast enhancements

Sparkle adds a few extra features to appcasts:

The appcast microformat should probably support these features as well.

The MD5 sum and DSA signature is specific for an enclosure. It is, however, not possible to add these extra attributes to a rel-enclosure link; a larger "enclosure" microformat may be necessary.


This proposal is mostly inspired by appcasts with Sparkle extensions.


		<div class="hentry">
			<h2 class="entry-title">Adium <span class="version">1.0.4</span></h2>
			<p>Updated on <abbr class="updated" title="2007-06-20T18:00+01:00">24 June</abbr>.</p>
			<div class="entry-content">
					<li>Fixed a crash introduced in 1.0.3 which could occur when accounts disconnected or status changed</li>
					<li>Fixed group chat when message history is enabled</li>

				<a href="" rel="enclosure">Download</a>.
				<span class="checksum">The <span class="type">MD5</span> checksum of this download is <span class="value">e0d123e5f316bef78bfdf5a008837577</span>.</span>.

The hash microformat used in this proposal is likely to change.

Multi-app/arch/OS/... appcasts

A single downloads page can have downloads for different applications, different versions, different architectures, different operating systems, etc (for example, the MySQL downloads page).

Here's a probably incomplete list of different download properties:

However, multi-* appcasts are hard to do right, and therefore probably not worth supporting. An appcast HTML page should therefore only contain updates for one application, one OS, one architecture, etc.

Software using appcasts

This is a list of programs and frameworks that use appcasts or appcast-like data.

Related Pages

appcast-brainstorming was last modified: Wednesday, December 31st, 1969