Well I guess it's written from a US perspective, where ER modelling caught on rather later than in the UK (using Chen notation rather than crow's foot notation, and other differences like allowing relationships to have attributes). But I think it was the ANSI-SPARC 1975 report that stimulated interest in "conceptual modelling", it wasn't the move to relational database technology. Very few people outside academia were interested in relational databases in 1975.

Michael Kay

Saxonica