[glue-wg] Comparison with CIM

[Laurence Field]

Hi Paul,

I think that Open Pegasus is actually a CIMOM and to be classified as a 
WBEM it has to use CIM-XML over HTTP, but I this is a minor detail which 
depends on the version. Implementations of the CIMOM have been around or 
a long time, I think you could even get it as a download for Windows 95! 
Some time ago I conducted an investigation on the potential for using 
this to replace the GRIS. The results are documented here if you are 
interested.

http://twiki.cern.ch/twiki/bin/view/EGEE/ProviderSpecification

There are a few features that were missing at the time, the main one 
being a caching mechanism to avoid to many queries throttling the resource.

It is important to understand the different in between aim of the DMTF 
and our aims. The DMTF is primarily concerned about management and this 
is the view from a service providers perspective, we are interested in 
the service from a consumers perspective. Paul Strong keeps showing a 
slide when talking about the reference model group of an "e-bookstore". 
This shows all the things that it takes to provide an e-bookstore such 
as database services, web servers, load balancers etc. This is what he 
wants to model, his data center,  so that the management can be 
automated.  For me this slide is only half the story, as users and 
higher level services, we are wanting to automate the use of the 
e-bookstore. We don't care how the services is provided, what we care 
about is things like; what kind of store is this?, what is the URL I use 
to interact with it?, can I pay with Pay Pal?, How long will it take to 
ship?, etc. It might be useful if we agreed on main entities such as 
books and payment :) however, the information model for these entities 
could be significantly different.

We have had a few discussions with people who are involved in SNIA but 
it hasn't really been very fruitful. I think it might just be that we 
are working in slightly different problems domains, provider vs 
consumer, and we don't really have spare capacity (sorry for the pun), 
to investigate further. Last year we did discuss the possibility of 
Felix going to a SNIA meeting in Germany but for some reason it didn't 
work out. Do you know if any of the dcache team have are involved with 
SNIA at any level?
>  My view is GLUE simply shouldn't publish any ACL information: a simple link from UserDomain to the objects that UserDomain might interact with should be sufficient, 
> right?  At worse, people try a service and find out they're not authorised  (which is an inevitable possibility, as GLUE can never publish all ACEs).
>   
I kind of agree with this but it is such a huge architectural change 
that it can't be done on a short timescale.
> Also, just as a general comment, I think GLUE's doing reasonably well at 
> keeping things simple, when compared to CIM's schema :-)
>   
People usually get scared with CIM as they see the whole schema. What 
usually happens is that you take a profile which only uses the bits you  
really need.  I guess the provider vs consumer differences means that 
the consumer schema should always be simpler.

Laurence