downloads-brainstorming
Downloads Brainstorming
The purpose of this page is to capture software download and sofware update practices in the wild, as one effort to codify practices currently used in the automatic update system called Sparkle.
This page was recently merged from appcast-brainstorming, and may therefore still have references to an "appcast microformat".
Authors
Context
Sites like iusethis.com, versiontracker.com, macupdate.com and download.com, among others, provide software downloads, both new releases and updates.
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.
Related Work
- hash-brainstorming has a section about hAtom integration. The example uses a "download" class, which contains a rel-enclosure link as well as a span with "md5" and "checksum" classes.
Sparkle-specific Appcast enhancements
Sparkle adds a few extra features to appcasts:
- External release notes URL: used when the release notes are not included in the appcast itself
- MD5 sums and DSA signatures: used for some extra security
- Version strings: Sparkle will try to determine the application version from the enclosure name, which is assumed to be APPNAME_VERSION.zip. If this is not possible, the
sparkle:versionattribute will be used. Thesparkle:shortVersionStringattribute contains the version string that will be displayed to the user (useful when the actual version number is an internal build number, for example).
The downloads 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 hentry in an downloads microformat can only have one enclosure, so the MD5 sum and DSA signature should be part of the hentry.
Proposal
This proposal is mostly inspired by appcasts with Sparkle extensions.
- Each hentry has one enclosure, and possibly checksums and digital signatures.
- Each hentry has one
versionwhich holds the application version.
Example:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
<html>
<head>
<title>Version History</title>
</head>
<body>
<h1>Version History</h1>
<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">
<ul>
<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>
</ul>
</div>
<p>
<a href="http://adiumx.cachefly.net/Adium_1.0.4.dmg" rel="enclosure">Download</a>.
<span class="checksum">
The <span class="type">MD5</span> checksum of this download is
<span class="value">e0d123e5f316bef78bfdf5a008837577</span>.
</span>.
</p>
</div>
</body>
</html>
The hash microformat used in this proposal is likely to change.
Multi-app/arch/OS/... download pages
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:
- Architecture: PPC, x86, 68k, architecture-independent, …
- OS: Mac OS X, Windows XP, OS-independent, …
- Download type: Ruby Gem, gzipped tarball, Mac OS X DMG, …
However, multi-* download pages are hard to do right, and therefore probably not worth supporting. A single HTML page should therefore only contain downloads for one application, one OS, one architecture, etc.
It's been suggested that tags could be used to mark up OSes and architectures.
Issues
Signatures
How should DSA signatures be handled? Should a simple <span class="dsa-signature">...</span> work? Should DSA signatures be part of the hash microformat (see hash-brainstorming)?
- digital-signatures seems to be useful, but only for signing microformat data, not enclosures.
- Is it really worth supporting DSA signatures in downloads? How many people use these DSA signatures anyway?
- Sparkle 2.0 will likely make DSA signatures a requirement. There will also be a tool that auto-signs updates. Something to keep in mind. DenisDefreyne 13:21, 12 Aug 2007 (PDT)
Smaller Download Microformat
Merging the appcast and the downloads microformat might not have been a smart idea, for the following reasons:
- The name "downloads" is very general and very vague.
- Marking up a single download with hAtom doesn't make much sense.
A simpler download microformat, which is basically a rel-enclosure with some extra data (MD5 sum, DSA signature) may be useful.
Naming
What name should this microformat have?
- "appcast": too specific? appcast shouldn't be limited to applications, and the term may be too jargony. Tantek doesn't like it.
- "downloads": too general? Chris doesn't like it.
- "software-updates": is "software" too general?
Version Numbers
Each entry needs a version number, so software update frameworks can figure out which version number to display. (Sparkle can actually figure out the version number from the download URL, but not always.)
In the proposal above, the "version" class name is used, but I'm not happy about it. In other microformats, "version" is used to indicate the version of the microformat, not the version of something that is described using the microformat. "revision" is probably a better name.
Overlap with Changesets
Changesets are very similar to downloads, with the exception that there are no downloads (another reason why the "downloads" name sucks?). Each changeset entry (hentry) usually has a short description (entry-title), a list of changes (entry-description), and a revision number.
To Do
- Create a hash microformat (see hash-brainstorming).
- Figure out how to include DSA signatures for enclosures.
- Figure out whether hListing could be used instead of hAtom.
- Figure out whether changesets can benefit from this microformat.
Software using appcasts
This is a list of programs and frameworks that use appcasts or appcast-like data.
- Sparkle uses Sparkle-enhanced RSS appcasts.
- AppFresh uses Sparkle-enhanced appcasts, including those generated by iusethis (e.g. the iGTD appcast).
- Spangle (formerly known as Perrier) uses Sparkle-enhanced RSS appcasts.
Implementations
The hatom-sparkle project on Google Code (project page, repository) is a fork of Sparkle that adds hAtom support. It is functional, but lacks support for shortVersionString as well as MD5 sums and DSA signatures.