[OGSA-D-WG] Fw: Definition of data consistency

Allen Luniewski luniew at us.ibm.com
Tue Oct 9 11:50:18 CDT 2007





Please see Jem's note below - he can not post to this DL.

I think that his suggestion is a good one.

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

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

----- Forwarded by Allen Luniewski/Almaden/IBM on 10/09/2007 09:49 AM -----
                                                                           
             "Treadwell, Jem"                                              
             <jem.treadwell at hp                                             
             .com>                                                      To 
                                       Dave Berry <daveb at nesc.ac.uk>,      
             10/09/2007 09:40          Allen Luniewski                     
             AM                        <luniew at almaden.ibm.com>            
                                                                        cc 
                                                                           
                                                                   Subject 
                                       FW: [OGSA-D-WG] ***SPAM***          
                                       Definition of data consistency      
                                                                           
                                                                           
                                                                           
                                                                           
                                                                           
                                                                           




Allen/Dave, I can’t mail the data mailing list, so please feel free to pass
this on if you think it’s worthwhile.

I agree with Allen about sounding specific, and this is a hard thing to
turn into a direct definition without using some term such as “indication.”
You might think about using an indirect form:

      Data consistency: An instance of data is said to be “consistent” with
      one or more other instances of that data if it is up-to-date with
      respect to those instances.

That may be enough, but you could also add something like:

      In a given system a policy may define the rules for determining
      whether data is up-to-date, and for maintaining consistency.

- Jem



Jem Treadwell
Software Engineer


HP ESS Software
856.638.6021 office | 856.638.6190 fax | jem.treadwell at hp.com
6000 Irwin Road | Mount Laurel | NJ 08054
http://www.hp.com/go/vse


hp

From: Allen Luniewski [mailto:luniew at us.ibm.com]
Sent: Monday, October 08, 2007 5:20 PM
To: Dave Berry
Cc: Treadwell, Jem; ogsa-d-wg at ogf.org
Subject: Re: [OGSA-D-WG] ***SPAM*** Definition of data consistency



Dave,

I think that I am okay with that suggested change. I am a little bit
worried about using the word "measure" as it can be taken to imply things
that we really do not want to address (e.g., a means to measure and a
quantifiable scale for measurement). I thought about suggesting changing "A
measure" to "An indication" but that seems just a bit too vague to me. I
don't have a better suggestion right now.

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

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

Inactive hide details for "Dave Berry" <daveb at nesc.ac.uk>"Dave Berry"
<daveb at nesc.ac.uk>


                                                                           
                         "Dave Berry"                                      
                         <daveb at nesc.a                                     
                         c.uk>                                             
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                         02:11 PM                                          
                                                   "Treadwell, Jem"        
                                                   <jem.treadwell at hp.com>  
                                                                           
                                                                   Subject 
                                                                           
                                                   [OGSA-D-WG] ***SPAM***  
                                                   Definition of data      
                                                   consistency             
                                                                           
                                                                           
                                                                           
                                                                           
                                                                           
                                                                           
                                                                           
                                                                           
                                                                           
                                                                           





Jem queried our definition of data consistency, which is currently:


|--------------------------------------------------------------------------|
| A policy that specifies or describes how up-to-date an instance of data  |
| is in one service of a distributed system, with respect to one or more   |
| instances of that data elsewhere in the system.                          |
|--------------------------------------------------------------------------|





Jem said (in e-mail):


my thought was that data consistency would be a state of the data - it's
consistent w.r.t. some other set of data or it isn't; the policy would be
the rules that determine whether it is, and what the requirements are.


I've had a look through our document and I agree. We refer to data
consistency policies but also to data consistency requirements, mechanisms
and strategies.

So, how about this as a revised definntion:

"A measure of how up-to-date an instance of data is in one service of a
distributed system, with respect to one or more instances of that data
elsewhere in the system."


Best wishes,

Dave Berry
Deputy Director, Research & E-infrastructure Development
National e-Science Centre
15 South College Street, Edinburgh, EH8 9AA
+44 131 651 4039 www.nesc.ac.uk
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