Adopting AppData in KDE?

[John Layt]

Hi,

I've been asked by Richard Hughes from Gnome and Fedora to raise the
profile of using AppData metadata within KDE.  I know very little
about this area myself, but thought it was worthwhile raising on the
list for discussion.  If you have any questions about AppData then
Richard would be happy to answer them, so please cc him on replies.

The AppData justification, file format and tools are documented at
[1].  AppData and AppStream are slowly being adopted by various
distros for use in their software installers and app stores.  The
AppData metadata file supplements the .desktop file by having a long
description of an app, links to some screenshots, and the app home
page, which get dispalyed in the app installer.  The description can
also be localized.  While distro's could generate and maintain this
data for themselves, to do so would be very time consuming for them,
may not present the app in the best way possible, and would quickly
get outdated.  It makes a lot of sense for apps to create and maintain
this metadata for themselves, presenting themselves in the best way
possible, which all the distros can then reuse in their installer
applications.

As far as I'm aware, AppData and/or AppStream is either used or
scheduled to be used by default in Gnome Software Centre, Apper,
Fedora, and OpenSuse, and optionally in several other distros, so is
not a distro specific intiative.  I think there's even OBS integration
happening.  If anyone knows more or thinks differently please let us
know.

Some recent developments make this a fairly high priority for apps
that wish to target a cross-desktop audience.  The new Gnome Software
Centre in Gnome 3.12 which uses AppData will become the default
installer in Fedora 20 for Gnome (Fedora KDE will use Apper).
Currently apps that don't provide AppData are ranked lower in search
results in Gnome Software, but from Gnome 3.14 such apps will not be
listed at all [2].  This means that without an AppData file KDE apps
will eventually not be visible to Gnome users in their default app
installer.  Currently Gnome has 50% of apps covered and is
coordinating an effort for full coverage [3], but KDE has only 1%.

Obviously individual apps are free to add these files [4], but from a
KDE-wide perspective we need to discuss if we want to officially adopt
this as a requirement, and if we want to provide a more coordinated
and standardized solution.  What do people think?

If we do adopt it, the two obvious issues to me are localization and
screenshots.  Ideally scripty would be hooked up to generate the
translation files, but as they are an XML format it may need a bit of
work.  Scripty would also need the AppData file to be in a standard
location in each repo.  The screenshots need to be hosted by the app
(at least initially, Fedora copy the screenshots to their own server
later to save load), so we may want to have somewhere common on the
KDE infrastructure for that.  I'd also suggest defining a file naming
standard including the app name and version number in the screenshot
name.

Taking a slight step-back, I wonder if there is a need for a more
generic KDE metadata file in each KDE repo that describes even more
useful info, like module, maintainer, reviewboard, bugzilla, last
stable release number, frameworks tier, forums, irc channel, userbase,
mailing list, etc, that AppData and projects.xml and inqlude and any
other required metadata files could all be automatically generated
from?

One obvious question is how this might relate to Bodega if KDE chooses
to switch to that?  What does Gnome shipping their own official "App
Store" mean for cross-distro/cross-desktop app store efforts and do we
need to start working on our own now, or will Bodega fill that need
for us?

Cheers!

John.

[1] http://people.freedesktop.org/~hughsient/appdata/
[2] http://blogs.gnome.org/hughsie/
[3] https://wiki.gnome.org/GnomeGoals/AppDataGnomeSoftware
[4] https://git.reviewboard.kde.org/r/113531/