Why does Lotus Notes change the UID of a calendar entry

My wife uses Lotus Notes at her current employer. It was a bit of a sick twist of fate as she'd left IBM for this new employer only to find that they too used Notes, a release or more behind IBM.

Anyway, I'd noticed while she was at IBM that any meeting notices which I'd sent her, would come back after she'd accepted as "meeting not on the Outlook Calendar". Finally tonight I got annoyed enough to look into it.

Now, it would not surprise me if Outlook was misbehaving, or Notes, or both, but it appears that Notes is at fault here.

See, there's a field called "UID" which gets sent in the meeting notice (I think it's vcal, but on inspecting a vcal entry and an ical format of the same entry I can't see much difference). Anyway, it's supposed to be a globally unique identifier:

Property Name: UID
Purpose: This property defines the persistent, globally unique identifier for the calendar component.

Outlook creates a very long string hex string like this:

UID:040000008200E00074C5B7101A82E00800000000D004EA628248C601000000000000
=20000010000000AB2E961CCB617F4BA1BE4C9882D938C9

That =20 in the second line is a vcal/ical encoding for a space which I believe is intended to indicate that it's a continuation from the preceding line, regardless of the field.

When the accepted notice returns from my wife's Notes system, it has a UID like this:

UID:A68A6A10CF9073EEADB18FFD5CC6EE4B-Lotus_Notes_Generated

Different, so Outlook reasonable replies that it knows nothing about this meeting (and since it's a METHOD:REPLY it's a bit confused as well).

Now, I don't have my own Notes setup and have no interest in setting one up just to debug this, but I did do a quick double check with Apple's iCal and the meeting acceptance response it returns does use the original UID value.

Now, there are many things I do not know, for example is this a Notes feature or a configuration option on the part of whoever's installed Lotus Notes? My interpretation of the RFC is that the value is supposed to be set by the requestor and not changed by any of the receivers.

And please, don't go down the path of why we send meeting notices to each other, it's an old ibm.com thing.

Further reading: Internet Calendaring and Scheduling Core Object Specification

Posted in Problems