No, you're right -- I had the same thought as 'Anon84 before I realized I was thinking of a different kind of language. The language 'Anon84 is thinking of is

No, you're right -- I had the same thought as 'Anon84 before I realized I was thinking of a different kind of language. The language 'Anon84 is thinking of is useful for thinking about concurrent systems, where each kind of bracket is associated with a particular agent. What's important is not that the brackets are mutually well-nested, but only that each kind of bracket is independently well-nested. This independence property means that "({)}" is a well-formed string, since ignoring everything but round parentheses gives "()", and ignoring everything but curly braces gives "{}". The Dyck language family is different. The entanglement between types of brackets means that you can't do a simple tensor like we'd like to.