Scoping Out-of-Context Attributes as Invalid?

[tajmone]

Currently, any attribute which is shared by more than one node is handled via the generic includes shared by all nodes.

Once all nodes and attributes are implemented, it might be worth to include an attribute only by the nodes which support it, and then in the generic includes shared by all nodes add a similar version which leads to invalid scoping of the attribute, due to it being out of context.

Since every node will first look for the supported attributes, the invalid variant should only match with those node that don't contemplate the attribute — although I'm not 100% sure of this, since I need to check if a non-specific attribute will pop-out of the valid node-attributes context, which would mean that any successive valid attributes would be treated as invalid.

If this could be implemented without too many problems, it might be worth considering it, otherwise the current method of just accepting any attribute in any node will do just fine (it's not the syntax's job to validate contexts, but if this can be achieved effortlessly, why not?).