I like this approach. Is it worth embellishing it as follows: Data consistency: An instance of data in one resource in a distributed system is said to be "consistent" with one or more other instances of that data elsewhere in the system if it is up-to-date with respect to those instances. In a given system a policy may define the rules for determining the extent to which data is up-to-date, and for maintaining that degree of consistency. The changes are: paragraph 1 - to talk about different resources in a distributed system (putting some context on "data instances", which is not a term we define). paragraph 2 - to introduce the notion of a degree of consistency rather than simply consistent/inconsistent. I don't feel strongly about either of these - what do others think? Dave. _____ From: ogsa-d-wg-bounces@ogf.org [mailto:ogsa-d-wg-bounces@ogf.org] On Behalf Of Allen Luniewski Sent: 09 October 2007 17:50 To: ogsa-d-wg@ggf.org Subject: [OGSA-D-WG] Fw: Definition of data consistency 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@hp.com> 10/09/2007 09:40 AM To Dave Berry <daveb@nesc.ac.uk>, Allen Luniewski <luniew@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@hp.com <mailto:jem.treadwell@hp.com> 6000 Irwin Road | Mount Laurel | NJ 08054 http://www.hp.com/go/vse <http://www.hp.com/go/vse> <http://www.hp.com/go/software> _____ From: Allen Luniewski [mailto:luniew@us.ibm.com] Sent: Monday, October 08, 2007 5:20 PM To: Dave Berry Cc: Treadwell, Jem; ogsa-d-wg@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) "Dave Berry" <daveb@nesc.ac.uk> "Dave Berry" <daveb@nesc.ac.uk> Sent by: ogsa-d-wg-bounces@ogf.org 10/08/2007 02:11 PM To <ogsa-d-wg@ogf.org> cc "Treadwell, Jem" <jem.treadwell@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 <http://www.nesc.ac.uk/> -- ogsa-d-wg mailing list ogsa-d-wg@ogf.org http://www.ogf.org/mailman/listinfo/ogsa-d-wg <http://www.ogf.org/mailman/listinfo/ogsa-d-wg>
