I think the issue is that Guillaume and I are viewing the group sequence as a simple, ordered set of instructions, whereas you, Gunnar, are viewing it more as a dependency graph. I will confess that I am having difficulty rising to your challenge of providing an example that would be indisputably cyclical without having sat down at a computer or with pen and paper to postulate one. In the meantime I wonder if there is anything in the spec to encourage this "dependency graph" interpretation of what a group sequence is. Having said that, it is probably true that a user who had set up such a situation as this had done so unintentionally. OTOH, the second attempt at validating the time consuming checks would be a noop in any case.