[OGSA-D-WG] Fw: Definition of data consistency
Allen Luniewski
luniew at us.ibm.com
Wed Oct 10 10:47:37 CDT 2007
Dave,
I like your enhancements. I vote for moving forward with this new
definition.
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 at nesc.ac.uk
> To
Allen Luniewski/Almaden/IBM at IBMUS,
10/10/2007 01:47 <ogsa-d-wg at ggf.org>
AM cc
"Treadwell, Jem"
<jem.treadwell at hp.com>
Subject
RE: [OGSA-D-WG] Fw: Definition of
data consistency
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 at ogf.org [mailto:ogsa-d-wg-bounces at ogf.org] On
Behalf Of Allen Luniewski
Sent: 09 October 2007 17:50
To: ogsa-d-wg at 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.tread
well at hp.co
m> To
Dave Berry
10/09/2007 <daveb at nesc.ac.uk>, Allen
09:40 AM Luniewski
<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.ac.uk>
Sent by: ogsa-d-wg-bounces at ogf.org
10/08/2007 02:11 PM To
<ogsa-d-wg at ogf.org>
cc
"Treadwell, Jem"
<jem.treadwell at hp.co
m>
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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