I went down a rabbit hole circa 2015 sketching out a system which was going to solve the language + world model problem which of course only needed to be partially implemented to solve a specific family of problems. In a broad sense think Palantir but with 20x the TAM because it is also an application builder.
I studied Xanadu a lot for this analysis because the system would need huge amounts of annotated text so it was requirement that "any" document could be marked up with commentary or structured markup turning the "explainable" idea bidirectionally so that humans could explain to the system what and why it is and the system could "talk back" in the same "language". Practically "any" reduced to HTML + PDF.
Transclusion was important to the vision because if, say, constants in a source code file came out of a standards document the link between the two ought to be preserved.
I can't say the internals would have looked like Xanadu at all and there wouldn't have been those micropayments.