ObjectGen is a tool for generating test objectives from use cases. ValueGen is a tool for generating operational variables and combination of values from use cases. Although ValueGen needs the artefacts generated by ObjectGen, both tools are independent.
The article illustrates a formal method of deriving functional test cases from use cases, including how to create a use case, derive all scenarios, and create reasonable test cases, as well as use IBM® Rational® RequisitePro for traceability from use cases to scenarios and test cases.