Sunday, 31 May 2009
Pushing it with HTTP...
a protocol and reference implementation for doing publish-subscribe
using web hooks, polling in feeds triggered by a ping from the
publisher, and POSTing Atom entries to notify subscribers. The
notification part is similar to what I've been working on for the
publish-subscribe stuff at Mediamatic Lab, where we spiced up Idavoll with an HTTP interface
to bridge the gap between XMPP Publish-Subscribe and HTTP speaking
Although I spend a lot of time working on XMPP based
publish-subscribe, I understand the reasons for going for a full
HTTP-based approach. XMPP can be intimidating for developers of web
applications. While the differences between XMPP and HTTP are
important (stateful connections, asynchronous processing, etc), the
fact that it is different is reason often enough. Hosting
facilities don't always offer ways to do XMPP, and there is not
nearly enough running code out there to make it easier for people
to play with these technologies to spice up their web application
with non-IM XMPP functionality. Having platforms like Google App
Engine provide sending and handling raw XMPP stanzas as part of the
API would surely help.
That said, PubSubHubbub has two separate sides to it, the
publishing part and the notification part. There's nothing that
prevents a hub to do the publishing part
using regular XMPP publish-subscribe. Instead of fetching the Atom
Feed over HTTP every time, it could use autodiscovery to find out
the publish-subscribe node and upgrade by subscribing to it
instead. Similarly, the notification part could send out XMPP
notifications. Combined with existing HTTP aggregator, that
combination is very similar to how the aggregator for Mimír works.
I'm still not convinced that PubSubHubbub is the answer to the
efficient exchange of updates on social objects, but I do think it is a
good way to make smaller entities be part of a federation of social
networking sites. Likely, we'll see a hybrid approach, to begin
The stuff we did besides throwing Frisbees...
Last month I was fortunate enough to attend Social Web FooCamp at
O'Reilly HQ in Sebastopol, CA, a follow up to Social Graph FooCamp in
2008. I can't express how inspiring such events are, being able to have
a continuous, in-depth conversation with so many bright minds about so
many topics that keep you busy on regular days,
and more. I'll give a quick overview of the whole trip, and then go
into depth in a series of posts.
My trip started with a visit to friend and former Jaiku colleague Andy
Smith, who was kind enough to take me in at Houseku.
As soon as I landed on SFO, I got an SMS from him to make a detour to
his office. Besides meeting a bunch of Andy's fellow googlers, I got to
spend some time with Brett Slatkin talking about
The next day I got a ride to Sebastopol from Edwin
Aoki. After a trip full of interesting conversation, we
arrived at the O'Reilly offices. Sebastopol was a lot warmer than San
Francisco, perfect for camping. Lots of familiar faces, but also a lot
of new ones. During the Friday evening, apart from the general
introduction, I didn't get to any sessions, but instead spent talking
to a bunch of people on XMPP,
and the work I am doing on federating social networks under that name
The next two days were filled with sessions and hallway talk on
OpenID, OAuth, different approaches to Publish-Subscribe and inter-site
communication, resource and service discovery and service scalability.
While most of the topics were similar to last year, I was glad to share
what we've done at Mediamatic Lab over the past year, while learning
how others have fared. We used these technologies to
make a true federation of social networking sites where you can make
cross-site relations between people and their social objects. Some of
our discoveries there we're shared among the participants, while others
had interesting other approaches.
Especially interesting to me was a session on OAuth and OpenID
where I could explain how we tried to improve upon the user experience.
Both technologies have a bad reputation in this area. With some smart
defaults and trust between sites, we could eliminate some of the
screens. There was talk about using pop-ups in some situations, either
as lightboxes or as new (small) windows. In our experience the former
can't be used if you want to do SSL (since you can't validate the
address and certificate). The latter was deemed confusing in our user
tests. Research is still ongoing, I suppose. The other issue had to do
with presenting OpenID providers. We currently use a drop down, but
that doesn't scale up very nicely. Logos might work, but in the end has
the same issue.
I also got to show Blaine Cook the code I wrote
recently to make it easier to write XMPP publish-subscribe enabled
services (code-as-a-node), that has been included in the recent Wokkel release. In turn, Blaine shared his thoughts on
addressing on the web and we got to hash it out with a bunch
of people like Brad Fitzpatrick, who also organized
the pubsub shootout session. Finally, Eran
Hammer-Lahav showed his work on XRD.
I'm pretty sure I forgot to mention a lot of things, but when it
comes back to me, I'll write about it some other time.