Building Blockchain Apps

17. Business Rules and Contracts

The blockchain virtual machine is essentially a state machine that reacts to state changes in the accounts (i.e., the transactions). Of course, as part of the reaction, the virtual machine can also cause additional state changes. In many cases, such state changes can be defined and described by sets of formal rules (“If this, then that,” or ITTT). In fact, in modern computer systems, most machine-to-machine interactions are defined by such rules.

However, when we have multiple interacting systems, explicitly coding and executing rules using a general programming language becomes impossible even for seasoned computer programmers. For example, in a typical airline mileage program, the points a person earns depend ...