Does pydelphin support any kind of interactive unification similar to LKB? For example, is there a way to easily see why a particular lexical item is failing to go through a lexical rule (when parsing with ace)?
PyDelphin doesn’t currently do unification at all. It can compute whether two types are compatible or if one subsumes the other, but it does not compute the result of unifying two feature structures. There are some other things it needs to do before this could be implemented, such as computing GLBs.
If you’re parsing with ACE and want to do interactive unification, you might try using LUI mode. The linked wiki isn’t very informative about interactive unification, but I think once you’ve popped up a parse in LUI mode, doing interactive unification is similar to how it’s done in the LKB. There’s a bit of information here, too.