[virt-tools-list] Re: libosinfo - another try

[Daniel P. Berrange]

On Thu, Oct 22, 2009 at 02:42:02PM -0400, Arjun Roy wrote:
> >> This would effectively force our view of the data as a graph, where the set of
> >> nodes are the set of distros and the edges are described by the structure
> >> attribute tags. (With a different graph resulting depending on attribute)
> >>
> >> 2. Informative Attributes
> >> This could refer to things such as name, kernel-type, architecture, or anything
> >> else that would be useful to track. I suspect that it would be alright to limit
> >> the kind of data to strings (kernel : linux) and version numbers 
> >> (kernel-version: 2.6.30).
> >>
> >
> > I kind of wonder if the 'version' distinction is even necessary, but I
> > don't think I could say for certain until we start trying to use the code.
> 
> The idea here was that you could search for distros with a kernel type exactly
> equaling linux (a string attribute) with kernel version *less than* 2.6.30,
> which implies special handling. But the more I think about it, I realize
> projects will have versioning methods that are wildly different enough that a
> one size fits all solution would be hard to implement. I'm looking for a good
> solution on this one.

> I mean, we need to be able to express that we are interested in a distro with
> a property foo that has version number bigger/smaller than a given version,
> right?

Version number comparisons are a really bad way to determine whether
functionality is available. RHEL-5 has 2.6.18 kernel, but has VirtIO
support which didn't appear until 2.6.20-something. 

If we need to determine if a particular item is available, we should
have an explicit piece for metadata for it. eg to determine if virtio
block is supported we should be checking a 'supported block devices'
tag of some kind, rather comparing version numbers. Version numbers 
should be purely informative, not used for any functional purpose

Regards,
Daniel
-- 
|: Red Hat, Engineering, London   -o-   http://people.redhat.com/berrange/ :|
|: http://libvirt.org  -o-  http://virt-manager.org  -o-  http://ovirt.org :|
|: http://autobuild.org       -o-         http://search.cpan.org/~danberr/ :|
|: GnuPG: 7D3B9505  -o-  F3C9 553F A1DA 4AC2 5648 23C1 B3DF F742 7D3B 9505 :|