Latest core taxonomy changes are breaking rdf_taxonomy

I would think that we can use a different way of handling this.
Your solution works but semantically, the http://www.w3.org/2004/02/skos/core#broaderTransitive predicate (which is the inverse predicate of http://www.w3.org/2004/02/skos/core#narrowerTransitive) should point to a resource.
That means that for the skos vocabulary, the '0' is not a valid value. This might create problems for us.

What we could use instead, is the base URI of the vocabulary, or the graph name or something. Explaining:
Usually, the vocabularies have a Scheme URI. Meaning that not only terms are having a URI, but the vocabulary as well.
For example, if a vocabulary has a base URL http://example.com/voc# then its terms should be

http://example.com/voc#term1
http://example.com/voc#term2
http://example.com/voc#term3

then we could use the http://example.com/voc# as the <root> term.

Otherwise, we could use some graph name, anyway, it is going to be a pseudo term.

Thanks for the work.