Re: [libvirt] [PATCH 1/2] Trivial fix: in dhcp-host the name is optional

On 02/15/2013 12:02 PM, Gene Czarcinski wrote: > Although in IPv4 one must pick either mac or name, either > can be omitted. Similarly, for IPv6, the name > can be optionally omitted. > Signed-off-by: Gene Czarcinski <gene(a)czarc.net&gt; > --- > docs/schemas/network.rng | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/docs/schemas/network.rng b/docs/schemas/network.rng > index 09d7c73..a479453 100644 > --- a/docs/schemas/network.rng > +++ b/docs/schemas/network.rng > @@ -281,7 +281,9 @@ > <optional> > <attribute name="mac"><ref name="uniMacAddr"/></attribute> > </optional> > - <attribute name="name"><text/></attribute> > + <optional> > + <attribute name="name"><text/></attribute> > + </optional> Hmm. This says that I can omit both name and mac, and still validate. Better would be this RelaxNG construct, which says that I must supply at least one, but can also supply both; the difference is that failure to supply either will cause a (desired) validation failure. <choice> <group> <attribute name="mac"><ref name="uniMacAddr"/></attribute> <optional> <attribute name="name"><text/></attribute> </optional> </group> <attribute name="name"><text/></attribute> </choice> I know Laine already ack'd but since we haven't pushed yet, I'm wondering if it is worth tightening the grammar.

The schemas are intended to provide a simple "syntax check" for XML documents that an app has created. eg detect typos in element/attribute names, or use of elements which don't use or incorrect nesting of elements. Even for syntax checks though, the schemas a not going to provide 100% coverage - todo so would make the schemas far more complicated and it is just not worth the effort. The XML parser is the ultimate place where 100% complete syntax checks are performed. What they generally do not do, is provide any kind of "semantic check" about whether the configuration actually makes sense. For example, the schema won't tell you that requesting virtio disks with a vmware guest is semantically invalid. This is left to the virt driver.