 The file system was fast and efficient, but was later replaced by Dominic Giampaolo's Be File System.Schillings also developed the graphics system for BeOS (known as the App Server), as well as programming frameworks such as the Interface Kit and Application Kit that are used by software developers to write software for the operating system.Before joining Trolltech in October 2005, Schillings worked as a "Distinguished Engineer" and CTO at OpenWave where, with Mike Reed, he led a team that developed Version 7 of the Openwave Phone Suite mobile phone applications.