Abstract. HECATAEUS is an open-source software tool for enabling impact prediction, what-if analysis, and regulation of relational database schema evolution. Our tool works seamlessly with a fairly large set of existing RDBMSs for parsing database schemata and workload definitions. We follow a graph theoretic approach and represent database schemas and database constructs, like queries and views, as graphs. Our tool enables the user to create hypothetical evolution events and examine their impact over the overall graph before these are actually enforced on it. It also allows definition of rules for regulating the impact of evolution and automates the adaptation to evolution events. Finally, it uses a metric suite for evaluating the impact of evolution events and detecting crucial and vulnerable parts of the system.