anyone can run a service that does stuff over nostr, that is basically a dvm, lets say a simple calculator, you would send an event with the params and the service(dvm) you want to use, could be via dm, or onthe event itself and the dvm would execute and give the result, the problem is trust, because someone is running the code and can run a badcalculator so afaik you dont have a way to do this trustless, bc we dont have a mechanism to execute the code we want in a trustless way.