1. There should be only one generic metamodel.

 To be the clue for interoperability, one part should have only one generic
 metamodel.

 This is also true for the information model part.



2. Object Role Models (NIAM) are better included if possible

 If it is possible, NIAM also should be included because practically the
 interoperability between a NIAM model and a usual E/R model is useful.

 But, even if NIAM is included, the information model part should only have
 one unified generic metanodel applicable for usual E/R model and NIAM.

 I do not think it is impossible, but if it is impossible, NIAM should be out
 of the scope.

OKABE, Masao



3. Bachman diagram and ISO 1033 Part11 Express (TC184) should be included as
  a kind of usual E/R model.

 The former is very famous (Is it almost the same as Ellis-Barker ?) and the
 latter is an international standard.