Feature Analysis of Business System 12 Ghica van Emde Boas-Lubsen Abstract: Business System 12 is the name of a Relational database system developed by IBM, in the Netherlands, in the early 1980-ies, building on the work of a group at Peterlee, UK. A first version of BS12 became operational in 1983. The system was never installed at a client; users accessed the system in a time shared environment. After IBM management had decided in the late 1980-ies no longer to support the system, it remained in use on behalf of a major application until 1996. In the database literature extremely little has been written about this system. The present report is a facsimile version of an unpublished internal memorandum at IBM Uithoorn; it describes the functionality of the system in the style as advocated in the book by Schmidt and Brody, {\em Relational Database Systems, Analysis and Comparison\/}, published in 1983. BS12 has a number of features which are rather unique for the Relational Database Systems, at least for those available in the 1980-ies. Its properties made the system particularly suitable for performing experiments in the field of deductive databases. This facsimile edition primarily has the purpose of making this information bibliographically traceable.