I have a large gedcom which I am wish to break into several different gedcoms. For example, I am trying to break out my half sisters tree and my tree into separate gedcoms. We have a common father, different mother. I would like to have a gedcom of my father which can be referenced by my gedcom and my sisters gedcom. Simply copying entries from my tree into my sisters tree is an unreliable solution. If something changes in our common father's tree, my tree and my sister's would require separate editing violating a basic principle of data integrity: don't have same data in more than one place.
There is no mechanism within GEDCOM 5.x to refer to another GEDCOM file in such a fashion that it is possible to process individuals, sources etc within that other file in an "intelligent" fashion. Some GEDCOM manipulating software will allow reference to external files in a manner which is always problematic since the GEDCOM standard isn't good at defining such links usefully. However, I know of no software that will interpret the target file as a GEDCOM - that doesn't mean that there isn't any such software, just that I don't know of any, and that such an interpretation is outside the GEDCOM standard.