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