> if one uses streams (monoids) instead of lists (trees) as the basic semantics, one has associativity for free I'm pretty sure that Krishnamurthi in particula

> if one uses streams (monoids) instead of lists (trees) as the basic semantics, one has associativity for free I'm pretty sure that Krishnamurthi in particular is very well aware of monoids. (I'm less familiar with the other author.) Are you thinking that the document's primary structure should be monoidal? That doesn't seem viable in the general case. You can, of course, represent documents in two different ways: a tree-structured index over a monoid or a monoidal representation over a tree - but that has a cost.