[OGSA-D-WG] Stab at Glossary Terms

[Dave Berry]

I think it's vital that we define these terms, because there has been a
lack of clarity for a while about the difference between data access and
data transfer.  The existing definition of data resource (originally
from DAIS) doesn't distinguish between these two modes in the way that
we do, using source and sink to implicitly refer to both.
 
Comments inline =>

	-----Original Message-----
	From: ogsa-d-wg-bounces at ogf.org
[mailto:ogsa-d-wg-bounces at ogf.org] On Behalf Of Allen Luniewski
	Sent: 13 April 2007 20:22
	To: ogsa-d-wg at ggf.org
	Subject: [OGSA-D-WG] Stab at Glossary Terms
	
	

	At today's teleconference we agreed that we needed to firm up
the definitions in our glossary of the terms Data Resource, Data Access,
Data Transfer, Source and Sink.  Currently only Data Resource has a
definition taken from the OGSA Glossary) as: 
	        An entity that can act as a source or sink of data
together with its associated framework. 
	
	The confusion that was identified centered on the use of the
terms "source" and "sink".  The above definition is using them in a
fairly generic way while the Data Architecture document uses them to
mean the source and sink of data transfers.  Here is stab at defining
all 5 of these terms.  Once we have agreed on the definitions, we may
need to do some minor edits to the architecture document as a result. 
	
	Data Access: Data access is any mechanism that allows an entity
to identify data held by a data resource and receive that data from the
data resource.  

Can I suggest changing "identify data" to "identify a subset of the
data"? 
 
I'm also not sure about saying "receive that data", as it may not be the
requestor that receives the data (i.e. the data may be sent to a third
party).  Would it work to say "and either return that data to the
requestor or to make it available for transfer elsewhere"?  I think
Mario had a suggestion for some phrasing that might be better than my
attempt here.

	Data Resource: An entity that can act as a source or sink of
data together with its associated framework.  By source we simply mean
an entity that can originate data.  And by sink we simply mean an entity
that receives data.  

I'm not comfortable with using source and sink in a generic fashion here
and in a more restrictive fashion elsewhere in the document (if this is
what you are suggesting).  I'd rather just refer readers to the glossary
definitions of these terms and make sure that all the entries are
consistent.
 
An alternative definition that I suggested was, "An entity (and its
associated framework) that supports a data access interface, or that can
act as a source or sink for data transfer", although I'm not strongly
wedded to that.

	Data Transfer: A mechanism to move data from a source of data to
a sink of data.  

Should we say "copy" rather than "move"?   Should we also say
"physically copy" or some such phrasing to distinguish this from a mere
renaming within a global namespace?

	Source: A data resource that contains that data to be copied to
a sink via a data transfer mechanism. 
	
	Sink: A data resource that receives the data copied by a data
transfer mechanism from a source.  

Currently we use "source" and "sink" to mean interfaces on a data
resource.  I think we should make this clear.  We could use the terms to
mean both the resource and the interface, provided that we are clear
about what we are doing. 

Allen Luniewski
IBM Cross Brand Services
IBM Silicon Valley Laboratory
555 Bailey Ave.
San Jose, CA 95141

408-463-2255
408-930-1844 (mobile)

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