iPhone SDK restrictions "troubling" to some

Apple yesterday unveiled its forthcoming iPhone Software Development Kit (SDK) during a town-hall meeting on its campus in Cupertino, but developers who read the company's own iPhone Human Interface Guidelines say the SDK comes with several troubling restrictions. TechCrunch reports that VoIP services are "basically out of luck," and developers can only use published APIs (Application Programming Interfaces) according to Apple's rules. The most significant limitation, however, is the fact that third-party iPhone applications can never run in the background and will immediately quit when users 'leave' the application to perform another action -- such as making a call.

Apple states in its iPhone Human Interface Guidelines that "Only one iPhone application can run at a time, and third-party applications never run in the background. This means that when users switch to another application, answer the phone, or check their email, the application they were using quits."

The afore-mentioned restriction severely limits the usefulness of some applications, such as instant messenger clients that should remain running in the background to collect instant messages from peers while users are busy performing other tasks. The limitation effectively renders useless a wide range of potential software for the iPhone.

iPhone applications also cannot write data to any location outside of their designated area, according to the report, which prevents developers from modifying data belonging to other applications. The latter restriction boosts security significantly and will severely hinder efforts by malicious users looking to write viruses or other harmful software for Apple's cellular handset, but will also prevent applications from working intimately with one another in various ways.