[ogsa-d-wg] RE: Data federation definition

[Allen Luniewski]

Neil,

I understand the definitions you used in your note.  But I still can not 
see how a federation service and an integration service are, in practice, 
any different.  Consider:

To do federation, a federation service is going to have to do schema 
integration.  Thus it acts as, or at least uses in your terms, an 
integration service.  If it does not do this, I do not see how it can 
perform its federation function.

In the definition of an integration service, I ask myself: what are the 
operations I can ask an integration service to do?  The only interesting 
answer I can come up with is: access data using the integrated schema. But 
this is just what a federation service does.

So I end  up where I started: the terms "federation" and "integration" 
are, in practice, indistinguishable.  I am willing to believe that the two 
are different but I am still looking for a way to tell them apart.

Allen




"neil p chue hong" <N.ChueHong at epcc.ed.ac.uk> 
Sent by: owner-ogsa-d-wg at ggf.org
01/27/2006 04:44 AM
Please respond to
N.ChueHong


To
"'Dave Berry'" <daveb at nesc.ac.uk>, "'Treadwell, Jem'" 
<jem.treadwell at hp.com>, <ogsa-d-wg at gridforum.org>
cc

Subject
RE: [ogsa-d-wg] RE: Data federation definition







Hi All,

I dredged up a response to a similar question I asked someone doing 
research
in the area a while back:

---
Federation means data sources that are autonomously managed and are
generally heterogeneous. It is also logical to say that the sources are
distributed (as a good cause for their autonomy and heterogeneity - but it
doesn't have to be the case as you can run multiple data servers on your
laptop.) 

Integration targets local and centralized managed data sources. 

There is also a difference between a global schema, federated schema, and 
an
integrated schema.
 - Global schema: result of integrating local schema into one global view
 - Federated schema: result of federating distributed schemas into one
global view
 - Integrated schema: integration of schemas "in preparation" to build a
global/federated schema. The main difference between integrated schema and
(global/federated) schema is in the integrated schema the elements "are 
NOT
YET" being mapped to their original data sources using (LaV, GaV, etc).

Check papers by Maurizio Lenzerini - "Data Integration: A theoretical
perspective" and others.
---

In general, I think we could say that a "data federation" service presents 
a
single consistent front end to a number of autonomously managed data
sources, whilst a "data integration" service uses some schema integration
tactic to map between data sources.

In that sense, the phrasing that Allen uses sounds like a data federation
service.

My 2p,
neil 


> -----Original Message-----
> From: owner-ogsa-d-wg at ggf.org 
> [mailto:owner-ogsa-d-wg at ggf.org] On Behalf Of Dave Berry
> Sent: 26 January 2006 10:11
> To: Treadwell, Jem; ogsa-d-wg at gridforum.org
> Subject: [ogsa-d-wg] RE: Data federation definition
> 
> Folks,
> 
> We need a definition of how we are using the term "data 
> federation", for the OGSA glossary.  Fortunately we don';t 
> have to find a definition that covers all the ways the term 
> is used in the world, just how we use it in our document. 
> Following a short discussion at the OGSA F2F, Jem (who is 
> keeper of the glossary) suggested the following;
> 
> The integration of multiple data resources so that they can 
> be accessed as if they were a single resource.
> 
> Allen suggested that as we are accessing data via services, 
> this would be better phrased as follows (see the attached 
> message for Allen's explanation in his own words):
> 
> The integration of multiple services or data resources so 
> that they can be accessed as if they were a single service.
> 
> We discussed this on yesterday's call and the consensus was 
> that I should post to the list and ask for your comments.
> 
> We briefly discussed whether we should separately define 
> "data federation" and "data integration".  One view was that 
> "integration"
> didn't necessarily involve distributed resources while "federation"
> didn't necessarily involve integrating the resources into a 
> single view.
> The contrasting view was that integration almost always 
> involves distributed data in practice, and especially so in a 
> Grid context, while federation typically requires some way of 
> accessing the distributed data as a whole.  So I'm leaning 
> towards treated the terms as synonyms within our documents.
> 
> What do you think?
> 
> Dave.
> 
> 
> 
>   _____ 
> 
>                From: Treadwell, Jem [mailto:jem.treadwell at hp.com] 
>                Sent: 19 January 2006 23:17
>                To: Dave Berry
>                Subject: Data federation definition
> 
> 
>                Dave: This is (very slightly) modified from your 
> document - though you don't have the glossary entry filled in :0)
> 
>                The integration of multiple data resources to so that 
> they can be accessed as if they were a single resource.
> 
>                - Jem
> 
>   _____ 
> 
> Jem Treadwell
> Hewlett-Packard Company
> 6000 Irwin Road
> Mount Laurel, NJ 08054 
> Phone:                 856-638-6021 
> Fax:           856-638-6190 
> E-mail:                 Jem.Treadwell at hp.com <
mailto:Jem.Treadwell at hp.com> 
> 
> 
> 


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