The Common Pipeline Library - a silver bullet for standardising pipelines?

The data from instruments of the VLT are automatically processed for standard basic data-reductions and artefact removal. Currently, such pipelines are operational for seven instruments and have been written on the basis of three different software packages. Since 2001, the Data Flow System group of ESO has been working on a Common Pipeline Library (CFL) which is based on code already developed and used at ESO and shall serve as the basis for all future instrument pipelines of the VLT. The main goals for the CPL are to streamline the code for different pipelines, to provide templates for standard algorithms, to support reuse of code, and to ease the maintenance and portability of the code. We describe the roots of the CPL code, the development process of the CPL and the problems we had to overcome to reach the current stable beta-release of CPL.