Content type of the list is not inherited from the content type of the site

There is exisiting content type with columns describ开发者_Python百科ed as xml schemes. We have to change column types of that content type to lookup. The problem is that content type of list doesn't inherit content type of the site that is described with those xml files. Can you please help?

The problem with setting a field to a lookup is that the definition of the lookup relies on the definition of the list already being set.

You would be better off creating new fields for the lookups in the derived content types.

It is hard to know the best approach without more information.