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Re: [Xen-API] New API Document and C Bindings

To: Ronald Perez <ronpz@xxxxxxxxxx>
Subject: Re: [Xen-API] New API Document and C Bindings
From: "Daniel P. Berrange" <berrange@xxxxxxxxxx>
Date: Fri, 15 Sep 2006 16:00:07 +0100
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On Fri, Sep 15, 2006 at 10:48:53AM -0400, Ronald Perez wrote:
> "Daniel P. Berrange" <berrange@xxxxxxxxxx> wrote on 09/15/2006 10:32:33 
> AM:
> > 
> > We are primarily talking about how to express things in the Xen API - 
> this
> > does not have to match how its expressed in CIM (provided we expose 
> enough
> > information in Xen API for CIM to doing a suitable re-mapping). For 
> example
> > in the Xen API we can express all domains the same way, but that doesn't
> > stop CIM expressing Domain-0 in a special Host class, seprate from other
> > guest VMs if that's appropriate for the CIM model.
> > 
> > Dan.
> 
> Thanks. So if John's "class hierarchy" were really a recursive 
> representation (as mentioned previously), that would be equivalent to your 
> "overlapping sets"? e.g., host_CPUs == VCPUs on a domU.

No they are not equivalent. There are scenarios you can represent with
overlapping sets which you can't represent in a hierarchy.  Consider
three sets  A, B, C.  A overlaps with B, B overlaps with C, and C overlaps
with A - there's no way to represent that as a hierarchy - hierarchies
can only represent directed, a-cyclic graphs - overlapping sets are 
non-directional cyclic graphs.

> How do you envision capabilities being represented? By the presence or 
> absence of a field/feature/method or a bitmap or ???

A set of flags perhaps. Depending on the type of capability was want to
represent, they're not all going to be associated directly with a domain.
Some like lifecycle states may be scoped to a domain object. Others
may be associated with sub-objects - for example a domain having privileged
access to a piece of hardware may be flags on their hardware specific object.

Dan.
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