How to generate test data using the OCL operation allInstances()

[killxin]

I have a problem when generating test data using the following model and OCL, which means "there are two instances c1, c2 of MyCollection, and the number of objects in c1 equals to that of c2 plus 1".

context MyCollection inv initial:
    MyCollection.allInstances()->collect(x|x.id)->includesAll(Set{1,2}) 
    and MyCollection.allInstances()->any(x|x.id=1).myobject->size() = 
        MyCollection.allInstances()->any(x|x.id=2).myobject->size() + 1 

Here is my code,

String UMLModelPath = "../EsOCLUsage/MyTest2.uml";
String constraint = "context MyCollection inv initial:"
	+ "MyCollection.allInstances()->collect(x|x.id)->includesAll(Set{1,2})"
 	+ " and MyCollection.allInstances()->any(x|x.id=1).myobject->size() = MyCollection.allInstances()->any(x|x.id=2).myobject->size() + 1"
        ;
OCLSolver oclSolver = new OCLSolver();
Result result = oclSolver.solveConstraint(UMLModelPath, constraint, new int[]{OCLSolver.OpOEA}, 5000);
oclSolver.printResults(result);

It fails to generate the target model and prints the error information:
no.simula.esocl.ocl.distance.FitnessCalculator ERROR: Instance not interpreted
If I use the simplified OCL as follows, it also returns false.

context MyCollection inv initial:
    MyCollection.allInstances()->collect(x|x.id)->includesAll(Set{1,2}) 

Since the OCL is very similar to

let c = Set{-1,87,19,88} in X.allInstances()->collect(b|b.y)->includesAll(c)

, A11 of TABLE 21 in the paper "Generating Test Data from OCL Constraints with Search Techniques"(TSE'2013), maybe there are some suggestions to solve the problem?

Thanks for your help!