db/journals/jacm/AbiteboulV89.html Serge Abiteboul Victor Vianu A transaction-based approach to relational database specification. 758-789 1989 36 J. ACM 4 http://doi.acm.org/10.1145/76359.76363 db/journals/jacm/jacm36.html#AbiteboulV89 JACM/36/P0758.pdf