[ogsa-wg] Nov 29 - Info Model call minutes

[Sergio Andreozzi]

Donal K. Fellows ha scritto:
> Sergio Andreozzi wrote:
>> Ellen Stokes ha scritto:
>>> One observation on your modified diagram....what do you mean by 
>>> 'Resource Model'?
>>>
>>> In OGSA, we use the terms information model (abstract) and data 
>>> model (concrete)....we do not use or define resource model since it 
>>> is an ambiguous term.
>>
>> yes, Information Model is a better term in that case. GLUE is a 
>> possible instance. I attach the modified version.
>
> I think you need to be careful with GLUE since that's very close to
> defining both an information model and a data model, making it easy to
> get confused. For example of how they differ, an information model might
> say that a particular class supports an extensible list of properties
> (other than the standard set it defines) and the data model would say
> what format that list of properties must take (e.g. XML document, Java
> properties format, comma-separated list, etc.) It's the information
> model that it is important to standardize at the architectural level,
> since it is fairly easy to code up data model transformations (though
> those matter much more for specific protocols).
GLUE is an information model of Grid resources. This is the main goal 
and nature.

The aspect of extensibility is secondary to this and is present because 
is a requirement from many parties. The fact that the abstract GLUE 
Information Model (represented using the object-oriented constructs of 
UML Class diagrams) is rendered on different concrete data models (XML 
Schema, relational and LDAP) makes it difficult to delegate at the 
concrete data model level the extensibility aspects. "Hooks" are 
currently present at the information model level and can be used to 
advertise information that is not currently captured by the 
specification without waiting for a new spec version. The GLUE Spec is 
deliberately not rigorous in defining the format of the content of the 
extensibility points.


Cheers, Sergio







-- 
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