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@us.ibm.com ----- Forwarded by Ellen Stokes/Austin/IBM on 07/10/2006 04:11 PM ----- Sergio Andreozzi <sergio.andreozzi@cnaf.infn.it> 06/20/2006 08:16 AM To Ellen Stokes/Austin/IBM@IBMUS cc Laurence Field <Laurence.Field@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//BOLO... ) 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@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