[Libvir] [RFC] Host and guest capabilities
Richard W.M. Jones
rjones at redhat.com
Wed Mar 7 14:56:47 UTC 2007
Daniel Veillard wrote:
> This sounds too variable, adding an entry point per capability of
> some of the hypervisor available will lead to just too many entry points
> once the set of virtualization engines and associated benefits increase.
> That's one of the places where I feel wy more comfortable returning an
> XML description which can then be augmented as more features are added.
But this API is _precisely_ designed to be extensible. The
virCapabilities structure is not accessible to callers (unlike, say,
virNodeInfo), except through accessor functions. We can add accessor
functions in future.
Returning XML just punts the problem elsewhere. Now clients need to
worry about parsing the XML, and there's no real guarantee that the XML
won't change in a way which is incompatible with the clients. Whereas
by using ordinary functions we have that guarantee.
Emerging Technologies, Red Hat http://et.redhat.com/~rjones/
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"[Negative numbers] darken the very whole doctrines of the equations
and make dark of the things which are in their nature excessively
obvious and simple" (Francis Maseres FRS, mathematician, 1759)
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