At the time, Forstall promised that the system would be available for developers come September.
Nor did it make an appearance during January's Macworld Expo keynote. In fact, it pretty much just .
"You know, we're late on this one," said Forstall as he announced push notifications again during Tuesday's iPhone 3.0 preview. According to the Apple VP, the response from developers to last year's announcement had been so enthusiastic that Apple started to think that maybe it had underestimated just how popular the notification system would be. So, said Forstall, the company decided to "rearchitect" the system from the ground up. "Now we're good to go," he concluded.
Despite that seemingly massive task, the capabilities and operation of the push notification system seem to be exactly the same as promised last year. Here's how it works: The iPhone keeps a persistent network connection via the cellular network to Apple's server, through which developers can send three types of notification: a badge update (à la the built-in Mail client), a text dialog (like when you receive an SMS message), or a sound alert. You can also combine multiple types of alert, as demonstrated by ESPN's Oke Okaro showed off a sports application that popped up a text dialog box while playing the familiar ESPN tone.
And that's it.
Obviously, it'll be a while before we can actually see the system in action, but the push notification system promises a modest improvement in the way that we interact with many of our iPhone applications. Instant-messaging programs, for example, will become more useful, since you can get messages without having to be running the application in the foreground (or resorting to workarounds like mail or SMS notification). News apps can now grab your attention when an update comes in. Social networking applications could let you know if you've received messages you might want to read.
But push notifications are hardly a panacea. Applications still can't run in the background, which hurts applications like third-party Internet radio applications, since you can't listen to audio from those apps while performing other tasks on the device. And as nice as notifications will be for instant messaging, in many ways it's a poor substitute for a true background-capable application.
According to Forstall, the reason Apple chose not to do background processes is primarily due to concerns for battery life and standby time--the company's tests showed that background processes gobbled up power like at a hot-dog-eating contest.
There are other usability questions about the notification system, too. For example, there's the matter of notification overload: Getting a text dialog box every time you get a new Twitter update would try the patience of even the most devoted Twitter user. Will the slew of notification-capable applications turn all of our iPhones into incessantly-chiming, dialog-box-spewing annoyances? When I'm on instant messenger, I'm often carrying on a few conversations at the same time; I could see notifications for each of those messages quickly becoming overwhelming.
It seems likely Apple or the third-party developers will provide a way to control the level of notifications on an application-by-application basis, or at least the ability to turn them on and off, but at least a portion of that responsibility will probably fall to the developer. That means all it takes is one poorly thought-out application to ruin your iPhone experience.
And despite the fact that Forstall stressed that today's iPhone push notifications are brought to us by the word "scalable," there remains the question of just how much Apple's system can handle. Could millions of Twitter updates--say, at an Apple event--bring the entire service to its knees? If there were , how does that bode for the notification system?
The amount of time Apple spent at last year's WWDC and on Tuesday's event explaining why push notifications are superior to background processes suggests to me that the latter is in fact what Apple would prefer to be doing, but the hardware just isn't there yet. The push notification system is a stopgap solution, just like Steve Jobs's claim that web applications were "a pretty sweet solution" for third-party developers who wanted to write software for the iPhone. Over 800 million App Store downloads later, we all know how well that turned out.
The real question is: are push notifications good enough to keep iPhone users happy until a more capable solution is possible? We'll have to wait until this summer to find out--well, assuming it actually ships this time.