With Shimano it is easy to find compatbile parts in a groupset because they will all share a model number system.
For example, Shimano 5800 series will consist of:
Does Campagnolo have a similar system?
It can be quite confusing since names such as "Chorus" are recycled between years; "Chorus 10 speed" is not enough to indentify a groupset.
If compatibility is what you're after, you should know that it's not always necessary to use the same group. Many times, you can mix and match different groups, even different manufacturers.
As far as I know, all 10-speed Campy geartrain components should be compatible with each other. You have to consider the capacity of both derailleurs relative to your gearing, but you have to do that even if using the same group for everything.
No, the components are identified by name and year even if they aren't changed every year. Spare parts do have exact part numbers, and most of the small parts are shared between multiple groupsets and year models.
Compatibility is generally not a problem, all series after the old "pointy ergo" 9-speed from 90s have same freehub bodies and actuation ratios.
