From the time Steve Jobs first aired the iPhone at MacWorld, software developers have asked, "Where's the Apple software development kit to produce independent applications?" Apple's answer so far is: No development kit.

But the iPhone desperately needs third-party applications. And some third parties are talking about the tools they can use to produce them.

One of the changes that the iPhone brings to the cell phone market is an ability to pull down data from Internet servers and display it in a suitably sized Safari browser window. Apple needs third parties to develop applications that work with that data. It's unlikely Apple can produce lots of customized, localized, and niche applications itself to suit all customer needs and tastes.

If no third-party applications materialize, then it's possible the current wave of enthusiasm for the iPhone will play itself out without building long-term customer satisfaction. The iPhone is geared to work with AT&T's Edge network, which is slow and underpowered as a service for the modern Internet consumer. It will be too slow for video downloads and can't sustain much in the way of fancy graphics. But what it can do is support bursty exchanges of data between Internet servers and mobile devices.

That's where Ajax development tools come in. Ajax-based applications reduce exchanges between client and server to a quick burst of data. Users get the new data they need; the network is engaged only for an instant. The Ajax style of programming may save the iPhone from being an overpriced gadget on an underpowered network.

An early example of potential third-party applications can be seen at izoho.com, where iZoho Writer, Sheet, and Show can be activated in the iPhone's Safari browser.

The iPhone's Safari browser can run HTML and JavaScript, one of the main components of Ajax. But building Ajax applications is time-consuming, if you don't have tools that recognize how JavaScript behaves in different browsers. And many developers have never produced a Safari application before.

That's why the developer blogger community is speculating that a handful of Ajax tools may emerge as the only entre for third parties to the iPhone, via the Safari browser window.

A leading candidate is Google's Web Toolkit, which includes cross browser capabilities with a substantial set of user interface components and JavaScript code libraries. Google is eager for developers to use its open-source toolkit for applications on the iPhone, which is already tuned to make use of Google Maps.