'Foundation for object/relational databases' is a proposal for the future direction of data and database management systems (DBMSs). It consists of a precise, formal definition of an abstract model of data, to be considered as a blueprint for the design of a DBMS and a database language. In particular, it provides a rock-solid foundation for integrating relational and object technologies, a foundation conspicuously lacking in current approaches to such integration.The proposed foundation represents an evolutionary step, not a revolutionary one. It builds on Codd's relational model of data and on the research that resulted from that work. It also incorporates a precise and comprehensive specification for a method of defining data types, including a comprehensive model of type inheritance, to address a lack that has been observed by many authorities; thus, it also builds on research in the field of object orientation. With a sound footing in both camps of the object/relational divide, the Manifesto is offered as a firm foundation for true object/relational DBMSs.