Systems Analysis and Synthesis

3.9. Shared Events

Real-world events often affect more than one atom. Borrowing a book from a library affects the state of the book and also the state of the borrower. We call such interactions shared events.

Often, a shared event involves a rate of exchange. Selling a book results in a loss of stock to the bookseller, but also an increase in money. The rates of exchange between books and money are prices . Rates of exchange are a second way in which numbers are important in a system.

The main point about shared events is that all parties to the event have to be in states where the event is permitted. That is so important, I shall say it again:

Each atom involved in a shared event must have an event-state diagram that includes at least one edge ...