I'm trying to use stocks and flows to create a model for my transportation game. Stocks correspond to nouns and flows correspond to verbs. At first I thought businesses would be stocks and the transportation of goods would correspond to flows. But I could also see the businesses as flows (since they consume and produce things) and the cargo areas and trucks as the stocks. Or maybe both trucks and businesses are flows, and only cargo areas (loading docks) and warehouses are stocks. Or maybe the cargo itself is the stock.
When it comes to a game, the player's decisions (and the AI's decisions) can directly affect flows, but not stocks. You can change the rate of production in Warcraft by hiring more peons, researching technology, etc. Production of gold is a flow. You do not directly change the amount of gold you have (except by buying something, but I think that's an instantaneous flow). Gold is a stock. There's no decision to be made with a stock—it just exists. There is a decision to be made with each flow, because you can throttle it back from its maximum. There are other decisions to make as well, but the basic resource management decisions (for gold, wood, soldiers, etc.) are about flows, not stocks.
In my game, the player controls the movement of trucks and the AI controls the businesses. The decisions are based partly on how much of each resource is available. I'm planning to treat trucks as stocks and the loading/unloading of them as flows. Businesses will be flows, but their cargo areas will be stocks.
The transfer of cargo is not enough to make an interesting game. The player will also need to make decisions about infrastructure and placement of transportation systems. The actual loading and unloading of trucks is boring; it's likely that an AI agent, acting on behalf of the player, will make those decisions. I still don't have a clear idea of where I'm going with this game, but it's already led me to some interesting topics (operations reseach, system dynamics, supply chain management).