A normal form object-oriented entity relationship (OOER) diagram is presented to address a set of 00 data modelling issues, viz. the inability to judge the quality of an 00 schema, the presence of inheritance conflicts in ISA hierarchies, the lack of explicit support for different relationship types (m;n, n-ary, recursive etc.) in some 00 data models and the lack of general and flexible support for views. Three approaches are described to translate good quality 00 schemas from a normal form

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... diagram. The first approach translates 00 schemas whoee underlying 00 data models support the notion of relationship. Thereare no undesirable redundancies in the translated schemes. The second approach provides for 00 data models that do not support the notion of relationship. Some redundancies may arise because of m-n, n-ary rek tionships, but these can be controlled. The third approach treats each 00 schema as au external schema of a conceptual schema represented by a normal form OOER diagram. Redundancies may' exist at the external schema level, but no redundancies exist at the conceptual echema level.