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.
C. Ardito, R. Lanzilotti, P. Buono, und A. Piccinno. Proceedings of the working conference on Advanced visual interfaces, Seite 278--281. Venezia, Italy, ACM, (2006)