Here's a question about the combinatorics of conceptual structure in WG which I've been wanting to ask for a while but hadn't wanted to send forth into a discoursal void.

In WG conceptual structure is formed from 'blobs', 'arrows' and 'isa-relations (IRs)'. 

1. IRs can connect arrows, but arrow X can isa arrow Y only if Y does not connect blobs. Why is this?

2. Arrows connect blobs, but cannot connect arrows. Why not?

3. A blob cannot isa an arrow that connects blobs. Why not?

In my work/thinking, arrows can connect both blobs and arrows. Or, more exactly, arrows connect only blobs, but such a blob can isa an arrow that connects blobs. This allows for, say, the dependent of X to isa a dependency between Y and Z. Dependencies are like headed binary branching phrases.

This is how Shaumyan's Categorial Grammar-like version of DG worked, as I recall, and also is similar to the way dependency is used in Dependency Phonology. It also tends to yield binary branching trees and the version of the basic combinatorics of syntax ('Merge') that is used in Minimalism.

--And.