Empire incorporates a simple downtime system that allows characters to gain new resources and wealth between events. In addition, the Imperial Senate receives an income every event from the Imperial treasury. Actions by characters at events and the ongoing plot can change the resources that are generated - but to ensure that this part of the system remains simple we employ a powerful principle to keep things simple - abstraction.
Keep it Simple
Every resource controlled by every character in Empire is different. One character may control a fleet which consists of a single great vessel, while another character owns a fleet of smaller ships. Farms may be large or small, fertile or barren; while a business could be anything that fits with the setting. Players are free to roleplay these details as they choose, within the remit of what makes sense within the system.
However no matter what a player chooses to roleplay - the income and wealth generated by a resource remain fixed. The different possibilities that players may imagine do not affect the simple rules that determine what wealth a resource produces. For the purposes of the rules we use a simple abstract - all ships and anything conceptually similar are just a fleet. A shop, a restaurant, a theatre or an opera house - in game terms all these things are represented by a business, the details are "below the abstraction layer" - they are ignored for the purposes of the game rules.
Below the Abstraction Layer
Detail and complexity that is below the abstraction layer is completely ignored by the rules. This provides a clear freedom to players - since it enables them to roleplay in whatever way is appropriate to the setting and their character's personal circumstances. If you want to roleplay that your character does not just own a farm - but is a pig farmer with a herd of prize winning pigs - then you are absolutely free to invent that kind of detail. The corresponding limitation is that these details do not affect the rules that govern the game - your farm does not produce more income than another character's farm - even though your pigs win prizes.
Any attempt by players to try to affect the game rules by delving "below the abstraction layer" will always be rejected by the game team. There are a number of ways that a character can improve the income from a farm - they can have rituals performed upon it, they can invest money to buy weirwood to make a farm bigger. But you can never increase the income of your farm through better husbandry - these details simply do not have a direct game effect other than in how you choose to roleplay them.
The Campaign Abstraction Layer
The abstraction layer also covers the elements of the game on the Imperial scale in places like the Imperial Military Council or the Senate. The general of an Imperial army is free to roleplay whatever appropriate leadership and training they provide to their army that makes sense for their character and the setting - but it doesn't change the effective fighting strength of the army as recorded by the rules system. If a general wants to improve the fighting abilities of an army - there are rituals and investments they can make that do that.
Likewise the treasury available to the Imperial senators is the sum of money that remains after a vast amount of taxation has been collected - and a vast amount of taxation has been spent administering the Empire. Expensive items - and items that the players can change - like the upkeep of armies and fortifications or the stipend for an Imperial title can be changed. But the minutiae of the fine details of how the civil service have made thousands of payments ensuring that the Empire can run are simply not part of the game. These details can't be changed, whatever changes might be made are simply ignored for rules purposes. The income of the Senate increases as the Empire conquers new territories and as they invest in more resources for auction through the bourse. It can't be increased purely by roleplaying that the civil service have become more efficient.
The Abstraction Layer is your Friend
On the face of it, the limitations imposed by the abstraction layer may seem restrictive. In fact the opposite is true - by ignoring these details, we don't have to play-balance them and that means we don't have to attach any rules to them - and that means complete freedom for players to roleplay as they choose provided the roleplaying makes sense within the context of the setting.
The true benefits of the abstraction layer come from the simplicity that they ensure. The game design strives to ensure that the complexity of the game is in the field - in the interactions between characters - not in the interactions between players and refs. A basic rules framework - with clear abstraction of the core ideas means the rules remain simple and much easier for players to understand. It works to prevent the rules becoming complex with time, as individual players seek rules clarifications for details that are being ignored by the system.
Having run games where the rules became increasingly complex over time, we are absolutely determined that that is not going to happen to Empire. We will continue to add new elements to the game over time, but all these elements will use the same level of abstraction and simple rules that apply to everything else in the game - so that the game becomes richer with more elements in it - but does not become more complex.