The villager walks through town, seemingly on it's way to the market stalls. It glances at other villagers that it passes by, waves at the occasional other villager, and even stops to chat with one. Upon reaching the market, it browses from one stall to the next, sometimes skipping one or returning to one it has previously visited. Along the way, it glances at other nearby villagers, stopping to bow to one in particular but then glaring suspiciously at the passing wizard. Eventually, after purchasing a couple items, the villager heads back home.
The town guardsman walks through the village as well. It strolls up and down the streets, looking at other villagers it passes, at doorways of local merchants, and even pauses to glance down the occasional alleyway. Upon passing another guardsman, he nods in greeting. But when he sees a superior officer he stops in place and salutes formally. He pauses at the intersection, looking around a bit before setting off down another road.
A dog dashes around with a small child, running and playing in the yard and street. They dodge out of the way of other villagers, and the dog pauses as it is distracted by the smell coming out of the butcher shop until the butcher steps out, sees the dog, and shoos it away.
A smith works in his shop, moving between the fire, the anvil, and a water barrel as he shapes something out of a piece of metal. Sometimes he goes from the anvil back to the fire and other times to the water barrel. After a bit, he quenches the hot metal in the barrel, drops the result in a pile and picks up another raw piece in the supply room.
The farmer, having been working in his field outside of town all day, heads into town and to the tavern. Upon entering the establishment, he waves to a number of his friends who are enjoying their own food and ale. Over the evening, he grabs a pint, some bread, and throws some darts with his pals. When the bard starts playing a song, he turns to watch, smiling and clapping along to the music with the other patrons—and cheering at the completion of the song.
As the sun goes down, a figure emerges from the shadowy alleyway, glancing around. When he sees that one of the town guardsman has passed by, he slowly heads toward the market stalls, still glancing around furtively. Upon reaching a stand with some fruits and vegetables, he takes one final glance around but, seeing a different guardsman coming his way, starts walking away again.
And none of this has been scripted! In fact, the next day, while things are similar, they aren't the same.
All of this can be done very easily with the tagging system in the IAUS. By placing tags marked with names such as "POI", "SOCIAL" and "PATROL", the ambient movement can be done easily.
Behaviors can be easily constructed to move to a nearby point that you haven't visited in a while. So, for example, the soldier, upon reaching a patrol point (and perhaps killing some time there looking around) will select another patrol point to move to. Again, the determination can be done by a combination of distance as well as the amount of time that it has been since they have been to that patrol point. The later point disqualfies (or at least discourages) them from simply moving back and forth between two patrol points. Throw in a tiny bit of randomness (easily done as a consideration in the IAUS) and the soldiers seem to move about in a way that is neither predicatbe, isn't entirely random, but falls squarely into the "reasonable" area from which believable behaviors arise.
If your level designer wanted to add another potential patrol point in town, all they need to is place another invisible marker tagged as "PATROL" and the NPC would immediately take it into consideration as a potential place to move to. Gone are the manually constructed "patrol paths" that not only take time to create, but are not as adaptable and certainly become more predictable through observation.
In the meantime, because of the way that the IAUS can interrupt and resume behaviors, the characters are free to act in other ways—such as looking, waving, or stopping to chat with a friend.
Similar to the patrol points, locations or objects can be tagged in other ways—even specific to the type of character. For example, the smith working in his shop will move between the anivl, fire, water barrel, supply room, and the pile of finished product. At each location, other behaviors can be designed to use those same tagged locations to trigger. For example, playing the animation for beating on a piece of metal would happen if the character was already standing at the anvil. If, for some reason, the level designer wanted to have two anvils, the smith could chose either one and act accordingly simply because of the "ANVIL" tag.
Other behaviors such as the looking at others (friendly or otherwise), waving at them, saluting them in the case of the soldier to an officer, or the dog sniffing around something it is particularly interested in, are easily created in the IAUS—often in minutes!