"

 Conceptual, logical and physical schemas
This paragraph opens with ""In 1975 ANSI described three kinds of data-model instance"".  They did but in 1975 it wasn't Conceptual/Logical/Physical as the para claims.  It was External/Conceptual/Physical, see the wiki article http://en.wikipedia.org/wiki/Three_schema_approach or look at the diagram alongside!
80.254.147.164  "