Dancing About Architecture

Over at FeedBurner we've started to offer publishers the ability to include links to Amazon.com items and (on a limited trial basis) advertisements in their feed. While this is sure to be a contentious issue, I personally think it's great to give publishers the option if they are looking for ways to monetize their hard work and effort. But that's neither here nor there -- I want to talk about some of the technical issues we've worked through to associate dynamic content within the unique constraints of feeds.

The number one big concern when you're dealing with feeds is: don't modify old items! There are few things more annoying than having an old entry show up as modified in your newsreader only to discover that the reason it's modified is that now there's an ad in the item. Lame. That said, we still give publishers the option to put ads in old items, but they are strongly discouraged from doing so:

Hmm ... maybe that should be stronger. Let me go talk to creative.

So that's the primary consideration. The next consideration is to remember that ads can get stale. But we quickly bump into the "don't modify items after the fact" rules again: if we need to change an ad because it's stale, how do we do that without modifying the entry? That's why we use images to display the ad. We generate an img src link once, attach it to the item, and then (with careful cache directive management) can change the image that gets returned from that constant URL over time. If the ad had been static text, the item would have been flagged as modified every time we refreshed the ad. If the ad was JavaScript, then it only would have shown up for 2% of the readers out there.

There's of course a bunch more stuff that goes into managing all of this, but I just wanted to let everyone know that we're really trying to respect the nature of this wonderful medium of feeds and not screw things up. There are going to be the people out there that cry "you've ruined feeds", but I really view this as filling a need that publishers have. It's been said before but I feel I need to reiterate: FeedBurner NEVER puts anything in the feed that the publisher doesn't want. If you see an ad in a feed, that's at the request of the publisher. We're going to be doing quite a bit of tweaking and tuning over the next few weeks before we open up some of the capabilities to a wider audience, but we all value your feedback.