Tuesday, September 30, 2008

iCalendar, CalDAV...then what? Part 2

After I received Alex Pline's email (posted here yesterday) I wrote to Lisa Dusseault, co-creator of CalDAV, and asked her for her thoughts. Here is her reply:

"Hi Scott,

"Alex is not wrong! iCalendar has interoperability issues and it's outmoded. However, those two issues aren't related. An XML-ized version of iCalendar risks having the same interoperability issues unless it's better specified. And even if it is, introducing xCal creates interoperability issues with the big deployed base of iCalendar users. Personally, I'm pretty pessimistic about changes like this being positive unless we have participation by Microsoft. However, if people want to push it forward, they can.

"Standards are made by the people who show up and do work. I hope Alex joins the CALSIFY mailing list or a similar list. He would be most welcome to endorse xCal and that might be part of moving xCal forward. The IETF is always extremely short of the type of contributors who manage issues lists and keep discussions on track."

Today while I was meeting with some other developers, another shortcoming of today's calendar-sharing technology became clear to me. Today, calendar-sharing usually involves email as a transport mechanism. For sending invitations, and RSVPs, these systems usually rely upon the store-and-forward protocol SMTP that underlies email.

Here's why that's a problem. I don't really care if my email takes a minute or two (or even longer) to arrive at its destination. But when I confirm that I've just accepted an invitation to enter a meeting, and if that meeting begins now or in a few minutes, I want that acceptance to appear everywhere it needs to right away, not in a few minutes.

This suggests to me that calendar sharing needs a more real-time protocol underneath it than SMTP. Maybe it needs to be based on something more akin to XMPP, the protocol underneath instant messaging.

Now it may be that iCalendar and CalDAV have all this thought through. Or, maybe not. I'm not an engineer. But put it together with Alex and Lisa's thoughts above, and you can see some of the places where calendar-sharing standards work needs to go next.

As for participation by Microsoft, there is at last some movement on that front. Check out Cameron Stillion's newly-posted comment on a post I made back on March 8. It speaks of Microsoft's "increased involvement" in CalConnect. I suspect I'll see more evidence of that at CalConnect XIII Oct. 6-10 in Santa Clara, California.

Got your own ideas of how to proceed? Send me your comments and emails.

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