Best way to refer from one entity span to another?

[kinghuang]

Given an entity Span object from Doc.ents, what's the best way to make a reference to another entity span for describing relationships between entities? My first inclination is to just declare an extension, and assign a span to it. But, the entity span objects are ephemeral, and it feels like doing it that way isn't correct. Is there a better way to store relationships between entity spans?

[polm]

It's true Spans are ephemeral, but they're tied to the Doc they come from, so I don't think putting a Span under its parent Doc should be a problem. That's the strategy used in the relation extraction component, which uses a doc._.rel extension, so for the relation A eats B you would have something like:

A = doc[...] # these are entity spans you got somehow
B = doc[...] 
doc._.rel = {(A, B): {"eats": 1.0}}

You can also use doc.spans for this purpose. The Spans in a SpanGroup are ordered so you can convey a relationship that way, though I think the extension might be clearer.

[kinghuang]

Thanks for the tips!