How can we figure out if a package is core or not?

[Alberto Salvia Novella]

Thomas Ward:
> I think it's relevant to read this discussion and the whole related
> chain to see how this decision on determining core/noncore had come
> forth, Alberto -
> https://lists.ubuntu.com/archives/ubuntu-bugsquad/2012-August/003869.html

Does 
<https://wiki.ubuntu.com/Bugs/Importance%20%28draft%29/Core%20packages> 
describe it well? or there's something that can be improved?

Thank you.