th0mas said:
Trade is the function of the population and the land. The goods which are traded, both unrefined and refined, are a product of the people on the land with commerse being the product of people trading the goods. So both people and the land are required.
Goods and commodities are a function of people and land. Commerce is not a function of land but of commodities, people, and distance. The commodities in Civ are strategic resources, luxuries, and food. However, you can have a tile that produces only a little food, but lots of trade. Conversely, you can have a tile produce massive amounts of food but limited trade. That's counter-intuitive. What are they trading? And with whom?
th0mas said:
Given it's scale there is an expected lack of granualrity when modelling local Socioeconomic activity. I have no problem with the current commerse abstraction as I think it fits this scale.
Consider this alternative. A city has population, culture, strategic resources, luxuries, and food. Together, those comprise its local economy. Those are factors that determine what that city has to provide other cities. The population is the market. The culture is for tourism/pilgrimages/etc. Strategic resources, luxuries, and commodities are obviously things other cities want. How effectively cities can meet each other's needs is determined by how easy it is to travel between them.
The actual commerce generated by a city is a function of the quality of its position in the trade network and the quality of other cities in the trade network. The quality of a city's position is how close it is to other cities. The quality of a city is the strength of its local economy. The trade between one city and another is the value that each derives from trading with the other divided by the distance between each one. The commerce (as in double-arrows that get converted into gold/science/luxuries) generated by a city is the sum of its local economy and all of its trade relationships with other cities. The trade for Shanghai would thus be the sum of the following:
Economy(city) = population + culture + resources + luxuries.
Trade(city1, city2) = Economy(city1) + Economy(city2)
Commerce(city0) = Economy(city0) + Trade(city0, city1)/distance(city, city1) + Trade(city0, city2)/distance(city0, city2) + Trade(city0, city3)/distance(city0, city3) + ....
for all cities that can be reached from city0.
An elaboration would be that cities that have the same commodities don't derive any benefit from trading those commodities to each other. Nobody in Newcastle is going to buy coal from somewhere else, so calculations of its trade with other coal cities would have the coal component removed entirely.
The distance between cities would be a function of terrain, technology, and infrastructure. The distance is the number of turns it takes your fastest unit to go from one city to the other (described further in
this thread, along with an earlier version of the above). This kind of trade can also cross borders, depending on the situation. A free trade agreement allows trade between your cities and their cities to be just like domestic trade. Having no trade agreement or being at war means there's no trade between cities. Then there are intermediate level agreements that can exist that allow some trade, but not at the same level as domestic (mechanism TBD).
th0mas said:
A rail line or road outside of anyone's territory by definition is not in use. If your territory expands to cover the line then you start paying maintenance. A rail line inside your territory is in use all the time and becomes part of the rail network.
Even if you're not working it? Let's take two adjacent rail segments connecting Samarkand with Bokhara. One of them is in your territory. The other is not. Neither is worked by a citizen. You move troops from Samarkand to Bokhara over both tiles. By any measure, they're both
in use to the exact same degree. So why should I have to pay maintenance on one but not the other? I believe there is no satisfactory solution to this problem, which is why there is no maintenance at all (as far as we know).