[ogsa-wg] [OGSA-D-WG] Definition of "data service"

[Subramaniam, Ravi]

Hi,

I would think that data is neither a resource, capability nor service. It is a unique entity/concept/essence. Thinking of data as a capability, resource or service can be problematic. 

Data is 'manipulated' by resources (could not think of a more appropriate word to represent the concept that I am thinking so I put it in quotes). To clarify data can be stored on a resource (storage), distributed by a resource (network), organised by or as a resource (file), operated on by a resource (CPU). Note: the items in parenthesis in the earlier sentence are resources (or more precisely resource types).  A service provides access to or a view of a resource (i.e. a *portal* into one or a set of resources) - this latter part is congruent with the WSRF approach. 

By this thought process, a 'data service' or 'data resource' is a misnomer. A service is a portal into or the external manifestation of a resource which in turn 'operates' (in a wide sense) on data. Part of the confusion appears on where in this 'concept chain' we are. So if we are at the resource level we introduce terms like 'data resource' or at the service level 'data service'.  

In the example on files in the earlier part of the thread: The file is a resource used to organise data. The operations performed on a file is the service that is the external manifestations of the resource (i.e. the file)

By this definition, we manage resources and not data. Actually data management is only achieved by managing the resources that 'operate' on data.

Ravi




Ravi Subramaniam

 -----Original Message-----
From: 	guru prasad [mailto:guru_bn at yahoo.com]
Sent:	Monday, July 09, 2007 07:55 AM Pacific Standard Time
To:	Donal K. Fellows
Cc:	ogsa-d-wg at ogf.org; ogsa-wg; Allen Luniewski
Subject:	Re: [ogsa-wg] [OGSA-D-WG] Definition of "data service"

> Thank you for your comments Allen.
> 
> In that case I vote for Dave Berry's definition:
> 
> "A service that provides interfaces to the capabilities and data of one 
> or more data resources within a service-oriented architecture."

There is a separate question as to whether the data *is* a capability; I
suspect it is, at least in some abstract sense. On the other hand, you
might wish to distinguish the data as a special kind of capability that
needs non-generic handling.


So can you suggest the modification to the definition that will incorporate what you just above?

"Donal K. Fellows" <donal.k.fellows at manchester.ac.uk> wrote: guru prasad wrote:
> Thank you for your comments Allen.
> 
> In that case I vote for Dave Berry's definition:
> 
> "A service that provides interfaces to the capabilities and data of one 
> or more data resources within a service-oriented architecture."

There is a separate question as to whether the data *is* a capability; I
suspect it is, at least in some abstract sense. On the other hand, you
might wish to distinguish the data as a special kind of capability that
needs non-generic handling.

> and the Data Resource is .....

A data resource is an abstraction of a file, so I'd imagine that you'd
want to describe it as a resource that is an ordered collection of
organized information. (The idea is that it doesn't have to be in a
file, but it does have many file-like characteristics.) It's strongly
beneficial to the overall OGSA if you can have data resources being a
subclass of resources (by referencing the OGSA glossary).

Donal.



       
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