The ECLiPSe system is to a large extent compatible with Prolog systems of the Edinburgh family, and one of the requirements during the development of ECLiPSe was to minimise the effort required to port programs written in other dialects to ECLiPSe. However, there are some differences. When you want to run an existing Prolog application on the ECLiPSe system, you have basically two choices: Using a compatibility language dialect, or modifying your program.