We have seen that the interleave pattern associates two different features and is both an unordered group and something that alters the way subgroups can be combined. These two features aren't totally independent because mixing child nodes is meaningful only when the order of the subgroups isn't maintained, but they aren't totally dependent either. In theory, it's possible to define a pattern with a meaning of "unordered group" that doesn't interleave child nodes and keeps groups unaltered.

This pattern doesn't exist in RELAX NG for two reasons. First, it helps keep the language as simple as possible. Also, although it is built on top of an abstract mathematical model, RELAX NG is also built on top of the experience of its authors who have wanted to focus on general usages and best practices amongst the XML community. The lack of a "unordered group with no interleaving" hasn't been reported as a real-world limitation so far.