Well, anyway, since I went to the trouble of disrupting this thread's line of discussion, I might as well put it back on a proper track...
At a basic level, I think the concept of technology is better-suited to worldgen cities than to the Fortress, itself.
There, production bonuses make far more sense, since all you have to really do is make that city produce more of a given type of product that can then be traded to your fortress. (I.E. a breakthrough in farming means more food, more population, and more craftsman off the farm that can produce goods for trade.)
Further, it's fairly natural for a fortress to basically be inventing the techniques through emergent gameplay, rather than overt declarations that you just got a +5 to food production. (Something that answers some of King Mir's concerns.)
For example, in an old thread on this topic, someone mentioned the technological innovations of farming of the Arabs... but what they innovated was largely public works projects like giant irrigation systems - something players can do if they want whenever they want. They're just "inventing it" whenever they decide to devote themselves to doing it. Same with the Romans - aside from concrete and maybe the arch, what did the Romans really
invent about their architecture? Their massive public works projects were more a matter of having the infrastructure to actually
do things like building extremely well-engineered roads and bridges and aquaducts, not that nobody had ever thought of concepts like pipes before. (Athens was built with plumbing, for one...)
Technology is often less a breakthrough, and more just a realization of how you can do more with an idea you already possess when you simply use that technology more. Dhokarena56 sent me a link to
this blog post recently, which had this passage that really grabbed me:
Jacobs mentions a settlement where her aunt was sent as a missionary. The aunt wanted to build a church from the large stones found in the riverbed; but the locals patiently explained that this was impossible. As everyone knew, mortar could only hold small stones; and even those could only be used for small structures like chimneys, certainly not a whole wall. This was not the Third World; this was 1930s North Carolina, and the people were descendants of people with a long tradition of stonemasonry.
To go back to what I said earlier, the basic technologies of glass-blowing and ceramics existed as long as civilization did (predating writing) but the technology to make
porcelain was frequently lost.
The problem is that few things in the game really have any capacity to make sense of
For notions like technological advancement to make sense, what you need is a system where a society has an invisible level that the game tracks for how much some civilization
uses the specific root technologies.
Porcelain was difficult high technology that came out of the existence of kaoline deposits in china for one, but also their extreme high-temperature furnaces (hotter than a magma forge is in-game) and the box fans that blew in concentrated air to burn the fires hotter devised thanks to their advances in metallurgy, as well as the fact that they could simply afford the people sent out to clear-cut forests for the charcoal it took to burn those furnaces so incredibly hot. (The technology was frequently lost when China simply couldn't continue to clear-cut forests to feed the fires anymore, often either because of deforestation or a need to send more peasants back to farming.)
However, the constant desire to get wealthy trading those goods kept them going back to re-learning the skills.
In order to represent this with worldgen cities, I think one of the best ways is to both track the overall number of skill ranks of every artisan in that city region (cumulative, not average) and use that as a means of unlocking different "levels of progress". Each new artisan of the same job would then start out with a bonus of extra skill ranks as the city became more specialized in how that city produced specific goods - they teach new artisans more about the craft, and it springs them on to become better artisans, themselves.
The more they trade things from that industry, the more of a bonus they get to this, encouraging more and more people to take up that craft, which further adds to their cumulative bonus to that technology. Eventually, a large portion of a city will be of a specific city specialty and they will all be masters from the instant they start their craft.
This can also influence Fortress Mode trade partners as well as migrants.
This can manifest as not just increased quality of goods, but also a flood more goods of that type. (More metal from dwarves, tamed animals from elves, etc.) They also could come bearing larger caravans in general being capable of bringing back more of your trade crap.
On Fortress-discoverables:
Things like steel, which I still believe there should be multiple quality gradients of iron below Fine Dwarven Steel, so that not all human iron is crap, can be something that is "discovered" through simply upping your own use of a given technology sufficiently.
That is, no waiting for some miraculous RNG blessing to give you something - if you just make ordinary steel in great enough quantity, and have legendary smiths, you get the technique for a slightly improved version of the metal. You earn it yourself.
Your fortress/city is its own driver of its own technology. You invent things through your own actions, rather than waiting for a gift from the Random Number God or spending points on a tech tree.
Thinking about it,
this ties in very well with Class Warfare. In that suggestion, it expands on the way in which you gain nobles through player actions, including recreating guilds through use of a given trade in your fort - guilds can also bring with them advances in functions to old technologies, or additions of new reactions or workshops.
For example,
vitreous enamel goods, such as, on the extreme end,
the Faberge eggs could be near-artifact level examples of high-end development of a specific line of artisanry.
Porcelain might require a mechanism-based air pump kiln and additional fuel, helping make it even more of a rarity. Porcelain isn't just stoneware with a rarer base resource and a slightly higher value multiplier, it's a top-tier crafting material. These can be "end-game" projects of examples of the height of developing a given craft in your fortress. (The whole point of Class Warfare being to actually give you a reason to want those goods besides for trade value.)
However, beyond even that, as people have pointed out, taming/domesticating an animal species is a form of technology. If we have Improved Farming implemented, specific crop rotations and the inclusion of pump-based irrigation or other techniques for getting more from your land are all technologies. Maybe these can have some invisible bonus (an overall "this society understands taming animals very well" bonus or
taxological bonus in addition to the species-specific bonus to taming) but they can mostly be "technologies" of what you, as a player, have tried to apply emergent techniques to doing better.
As an added amusing bonus, the game could reflect increases in worldgen city farming because of techniques that you have "discovered" in your own fortress. (Although given how Toady tends to work things, that would mean that if you created an irrigation system, it wouldn't actually apply unless worldgen cities were capable of procedurally building their own aquaducts and irrigation systems, themselves...)