Correction: It is currently not possible to have a class belong to two facet-groups.
Another question is if perhaps it is better to let the compiler always create the facet group object when it first encounters the facet keyword, and by implication having the object group "argument" be a program instead of an object. If so, is it possible to have the facet group definition and the facet users in the same file, if the facet is "updated" on the second compiler pass.