Returns a collection containing all the elements contained in self on which we applied the OclExpression expr. The results won't be flattened. The type of the resulting collection depends on the type of self.

For the purpose of these examples we'll assume here that we have a Class *Person* with a reference *children*. Our model contains two persons such as *person1.children = {James, Jane}* and *person2.children = {John}*.