Every software center that exists allows the user to look at
screenshots and a long description of the application before it is
installed. For most users it allows them to answer the question Do
I want to install this application?

Traditionally in Linux distributions, we have none of this data
for the vast majority of our desktop user-installable applications.
To solve this, we have defined a new data file, which the upstream
project can optionally translate using the same technique as GSetting
schemas or Desktop files. Rather than create a new schema from
scratch, we'll be using a subset of the AppStream metadata proposal.
