This approach has lead to significant inefficiencies, risks and inflexibilities as one of the parties is bearing all the costs of building, maintaining and operating the portal.

Now, instead of reusing nails, we're reusing foundations and load-bearing walls like pieces of a pre-fabricated building.

So how do you create a three-story bookstore in a cathedral when you can't drill any holes into the building or attach anything load-bearing to its walls?