[ogsa-wg] Fw: info model XML representation

Mon Jul 10 16:13:43 CDT 2006

Feedback from the GLUE schema person I've been working with...to factor 
into our info model discussions.
Appears additional collaboration with Sergio is welcome.
Ellen

Ellen Stokes
STSM, Grid Computing
TC Member, IBM Academy of Technology
Austin, Texas
tl 678 0552   outside +1 512 838 0552
stokese at us.ibm.com

----- Forwarded by Ellen Stokes/Austin/IBM on 07/10/2006 04:11 PM -----

Sergio Andreozzi <sergio.andreozzi at cnaf.infn.it> 
06/20/2006 08:16 AM

To
Ellen Stokes/Austin/IBM at IBMUS
cc
Laurence Field <Laurence.Field at cern.ch>
Subject
Re: info model XML representation

Dear Ellen,

I read the document and found it interesting. As regards the main 
question (which of the two proposal is preferred), I have not a clear 
answer yet since this depends on the final goal of the paper. Below you 
can find my considerations:

Some preliminary statement:

1. the GLUE Schema models Grid resource characteristics
2. the JDL is used to describe a job request; requirements on resources 
can be expressed based on GLUE Schema-related attributes
3. JSDL models a job description, hence it contains requirements on 
resource characteristics; the requirements are expressed over a set of 
characteristics inspired by CIM; this set of attributes can be 
"isolated" in a Resource Requirement Language (RRL)

so the proportion: JSD : JSDL = GLUE Schema : RRL

The document describes a solution to both model resource characteristics 
and requirements on resources. In order to better position the paper, it 
would be useful to state:

1. relationship between the proposal for describing resource 
requirements and the JSDL Resources Elements; Figure 1 can help in 
understanding, nevertheless it would be better to write it more explicitly

2. better state the goal of the modeling, in the sense that it should be 
more clear if the purpose of the document is to describe a modeling for 
enabling a resource selection process; (also in the abstract);
a possible discussion on the matchmaking approaches using this modeling 
could also fit the paper;

3. it is generally more acceptable to write about "a Grid" or "the 
Grids" instead of "the grid", since there is no a unique Grid as it was 
envisioned in the early years of this paradigm

4. about the two possible approaches, at a first glance, I do not lean 
to a particular approach; some comments below:

Proposal I - Using XML typing and extensibility

pro:
* enables better data quality enforcement since it relies on XML Schema 
data model
* characteristics modeled as XML elements (instead of attributes) give 
more flexibility in defining complex type

neutral: there is no a symmetric approach in the description of 
resources and activities

consideration about the node entity; considering the GLUE Schema 
experience:
- resources are managed by batch systems and are organized in pools 
exposed to the Grid layer
- for scalability reasons, there is no description of single nodes, but 
description of homogeneous set of nodes, i.e., homogeneous execution 
environments for applications; this implies that only static 
characteristics are modeled and advertised (e.g., TotalMainMemory is ok, 
FreeMainMemory is ko); dynamic attributes can be added if they refer to 
aggregation (e.g., MaxFreeMainMemory, that is the highest free main 
memory among the nodes present)
- an important aspect is the service differentiation, that is, do all 
Grid users have the same possibility to access a resource or not? this 
is currently a hot topic and the solutions being investigated adopt the 
creation of different shares/priorities assignable to different 
groups/roles hold by users; this means that the resources are the same, 
but the selection process should be able to consider the QoS aspect;
these aspects are important in a resource selection process

Proposal II - Using typing outside of XML

this approach is schema-free and symmetric (a la ClassAd);

One more general comment. An important requirement for a selection 
system is to be able to express preferences that are used to choose the 
best resource among the available ones that matched the 
hard-constraints. This topic was the core of my PhD thesis that you 
might be interested looking at:
(
http://www.cs.unibo.it/pub/TR/UBLCS/ABSTRACTS/2006.bib?ncstrl.cabernet//BOLOGNA-UBLCS-2006-02
)

For resource description, the undertaken approach is close to your 
proposal I; for requirements and preferences, I've defined a tailored 
language inspired by XQuery (it is called XMatch).

I would like to have your feedback about these considerations. Consider 
also the possibility of writing a joint paper.

Cheers, Sergio

Laurence Field wrote:
> Hi Ellen,
> 
> I think that Sergio is the correct person to comment on this.  I have 
> cc'd him,
> 
> Laurence
> 
> Ellen Stokes wrote:
> 
>>
>> Laurence,
>>
>> As part of the information model direction that the resource 
>> management design team is pulling together (part of the GGF OGSA 
>> workgroup), we are considering 2 alternatives for the XML 
>> representation of an information model.  We've discussed the pros and 
>> cons of each proposal, but have come to no conclusions or 
>> recommendations.  So, we've decided to solicit the opinions of groups 
>> that use information models and have an XML representation.  And the 
>> EGEE's G-lite work is one such group. 
>> I'm not sure if you're the right person to work with to solicit an 
>> opinion on XML representation.  If not, please let me know who I 
>> should talk with.
>>
>> I've attached the document.  Section 3 proposes the overall direction 
>> for modeling resources in the grid.  Section 4 provides an example 
>> (take the example at face value - it's just an example so don't worry 
>> about details of the reousrces modeled) and proposes 2 alternative XML 
>> representations.  I'd like to understand G-lite's opinion on which 
>> representation should be used to model resources in the grid and why.
>>
>>
>>
>> Thanks.
>> Ellen
>>
>> Ellen Stokes
>> STSM, Grid Computing
>> TC Member, IBM Academy of Technology
>> Austin, Texas
>> tl 678 0552   outside +1 512 838 0552
>> stokese at us.ibm.com
> 
> 

-- 
Sergio Andreozzi
INFN-CNAF,                    Tel: +39 051 609 2860
Viale Berti Pichat, 6/2       Fax: +39 051 609 2746
40126 Bologna (Italy)         Web: http://www.cnaf.infn.it/~andreozzi

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