[ogsa-wg] Glossary terms for Thursday's call (state definition)

[Strong, Paul]

I think we need to modify Jem's definition slightly.  A component has to
be manageable before it can be configured.  Thus it exists before it is
configured :o)  This is the goal of the Ref Model life cycle where we
have the notion of -
 
Extant - the component is manageable, i.e. it can be configured
Configured - the component has been configured sufficently to allow it
to be started
Active - the component is serving the purpose for which it was intended,
i.e. responding to requests, doing a calculation etc.
 
I find a useful way of thinking about this is that state is really
reflected by attributes that cannot typically be set externally.  Whilst
configuration parameters may be.  Clearly state may be changed by
applying verb externally to a managed component, such as start or stop,
but this is not the same.
 
Paul
 
 

________________________________

From: Michael Behrens [mailto:michael.behrens at r2ad.com] 
Sent: Tuesday, May 01, 2007 1:54 AM
To: Treadwell, Jem
Cc: Donal K. Fellows; Strong, Paul; ogsa-wg; rm-wg at ogf.org
Subject: Re: [ogsa-wg] Glossary terms for Thursday's call (state
definition)


Most insightful.  Would the available attributes vary directly with the
lifecycle state of the resource?  Or would there  simply be a  way to
categorize attributes and might this affect future resource
specifications?

Treadwell, Jem wrote: 

	Paul/Donal/All,
	Thanks for the comments, and sorry to be slow in responding -
I'm not
	able to work on this quite as much these days :(
	Now that I've taken time to read Paul's comment and Donal's
response a
	little more carefully, I think Donal makes an excellent point -
I would
	expect that an entity would exist only after it has been
configured. Its
	configuration attributes would *contribute* to its state, but
would not
	be a part of it unless the details are associated with (*maybe*
	contained within) the entity, are visible to some external
observer
	(possibly a debugger), and might change.
	I'm happy to add a little more explanation in the definition if
anyone
	thinks it would be helpful. For example, at the end of Para 1 I
could
	add: 
	  Configuration attributes typically affect an entity's initial
state,
	  but would not be considered to be part of the state unless
they
	  can be changed during the entity's lifetime, and thus affect
its
	  behavior.
	Other suggestions welcome!
	- Jem
	
	
	  

		-----Original Message-----
		From: ogsa-wg-bounces at ogf.org
[mailto:ogsa-wg-bounces at ogf.org] On
		    

	Behalf
	  

		Of Donal K. Fellows
		Sent: Friday, April 13, 2007 4:38 AM
		To: Strong, Paul
		Cc: ogsa-wg; rm-wg at ogf.org
		Subject: Re: [ogsa-wg] Glossary terms for Thursday's
call
		
		Strong, Paul wrote:
		    

			Within the RM-WG we have split attributes into
configuration
			      

	attributes
	  

			and state attributes.  Configuration attributes
to some degree
			      

	define
	  

			behavior, defining or constraining the set of
allowed states, as
			      

	well as
	  

			the possible values of state attributes and
allowed transitions
			      

	between
	  

			states.  Clearly configuration attributes are
"interesting", and
			      

	thus
	  

			according to the definition below they would be
considered part of
			      

	the
	  

			state.  I'm not sure that this is the case.
			      

		An argument that I made during the call (and which it
might have been
		nice to have delved into in more detail if we'd had a
few days instead
		of 15 minutes!) is that an altered configuration creates
a different
		resource/stateful entity[*], but an altered state is
something that is
		expected during the normal working lifetime of a
resource and does not
		change the fundamental nature of that resource. That is,
a change of
		config is qualitatively different to a change of state,
even if both
		    

	are
	  

		(represented as) attributes.
		
		In general, there are loads of definitions of state
(I've got a
		background which leads me to regard it as really a
partial function
		whose domain is the cartesian product of time and names
for "stateful"
		things) but they're just different ways of looking at
the same thing.
		The good aspects of the current definition are that it
is observable
		    

	and
	  

		changes in it are events, things which are not implicit
in the
		    

	standard
	  

		CS definitions of the term and yet are very useful for
grids.
		
		Donal.
		[* As you can tell, I've lost track of what kind of
thing contains
		    

	such
	  

		    attributes. I know *I* think of them as resources,
but that
		    

	doesn't
	  

		    make me right. :-) ]
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-- 
Michael Behrens
R2AD, LLC
(571) 594-3008 (cell)
(703) 714-0442 (land)
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