Let's say
Taxonomy_A is associated to Node_Type_A
Taxonomy_B is associated to Node_Type_B.AND
Both Taxonomy_A and Taxonomy_B have a term called 'yellow'.
Is it possible to make terms 'yellow' synonymous, so that if I'm looking at a list of 'yellow' stuff, I'm seeing content of both types (Node_Type_A, and Node_Type_B)?
Progress:
Unfortunately it is not possible for taxonomy terms to behave in Drupal as described in my question (at least not without forcing it):
It is clear by taking a look at the terms_related table that it would be possible to create paths that forced related terms together using the taxonomy_get_related
function regardless of what vocabulary the term belongs to:
However, the way to get to these terms is through the taxonomy_get_related
function in the taxonomy module. This function is not used at all in drupal-6 core except to define it. (I did find it once in the ctools module).