MOF26 — org.omg.emof.oppositeRoleName

The oppositeRoleName tag was introduced to support inverse navigation by OCL expressions since an OCL navigation needs to know the name to be navigated. An OCL navigation also needs to know whether the far end is a collection or not, and, if it is a collection, whether it is ordered and/or has unique values.The vast majority of opposite end characteristics can be reconstructed by assuming [0..1] !ordered, unique. However for the UML 2.5 model, this erroneously characterizes one ordered collection as not-ordered, about 10 lower bounds as 0 rather than 1, and about 100 upper bounds as 1 rather than 2 or *.

If EMOF is to be useable by OCL and related tools, additional
org.omg.emof.oppositeLower
org.omg.emof.oppositeUpper
org.omg.emof.oppositeOrdered
org.omg.emof.oppositeUnique

tags are need to avoid corruption of metamodel relationships.

(The discussion on Issue 12800 that introduced oppositeRoleName suggested that the above might be necessary. Experience has shown that they are necessary. For instance for QVTr, a QVTc middle metamodel is synthesized with unidirectional navigation to the user metamodels. These unidirectional relationships are navigated in reverse as part of the trace and must have correct multiplicities.)