On 3/30/09 11:40 PM, Curtis King wrote: > > On 30-Mar-09, at 7:12 PM, Peter Saint-Andre wrote: > >> As far as I can see, nothing in XEP-0237 (Roster Versioning) prevents a >> server from using timestamps (e.g., seconds in the Unix era) as >> version/sequence numbers. Would that be a popular approach? If so, we >> might want to add a note about it in the spec. > > time makes a bad counter as it can go backwards and there are resolution > issues ;-) > > Instead follow rfc4551 for version number, > > An IMAP server that supports this extension MUST associate a positive > unsigned 64-bit value called a modification sequence (mod-sequence) > with every IMAP message. This is an opaque value updated by the > server whenever a metadata item is modified. The server MUST > guarantee that each STORE command performed on the same mailbox > (including simultaneous stores to different metadata items from > different connections) will get a different mod-sequence value. > Also, for any two successful STORE operations performed in the same > session on the same mailbox, the mod-sequence of the second completed > operation MUST be greater than the mod-sequence of the first > completed. Note that the latter rule disallows the use of the system > clock as a mod-sequence, because if system time changes (e.g., an NTP > [NTP] client adjusting the time), the next generated value might be > less than the previous one.
Thanks for the text. That looks helpful. I'll borrow accordingly. Peter -- Peter Saint-Andre https://stpeter.im/
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