Think of multisig, which we have the machinery for but not enabled yet. So you have several data points (Mutable Data) which represent agreements of sorts. So App A agrees and sign’s an MD to do something (swap owners or whatever it is supposed to do, add comments, or change data etc.). It sends the signature (this is the part we have not agree on, this send signature part) but the MD will not change until App B agrees conditions are met. Then it to can sign the MD And it will change.
You can expand a lot on this pattern and have “smart contracts” a term that has become widely overused. I prefer to think of this as network agreed logic. In any case this is a huge area, but I think many folk will see this simplistic pattern above is the basis for smart multi level contracts that execute in a domino type effect but clearly so and can depend on in network “oracles” (another term I hate) or worst case out of network oracles (which I feel invalidates many contracts, smart or not).
Hope that helps.