John Chen, CEO of Sybase, has left his position after staying on to aid it in its integration into SAP. Chen had been with Sybase since August 1997 when he joined as chief operating officer and served as Co-CEO from February through November 1998 and had held the CEP position since then. Before that, Chen was CEO of the Open Enterprise Consulting Division of Siemens Nixdorf from 1995 through 1997