Making the AI not build a unit

Does anyone know what, i need to put in the unitinfos.xml to have the ai not build a unit type, i'm sure this is the file i need to edit as it has all the unit attributes and unit AI types but i don't know what to put in place of the default unit AI

You should ask questions in the main creation and customization forum, and should PM a moderator to have them move this thread. Default unit AI tells the AI what to use a unit for, not wether to build it, though if you give it something inappropriate (give a melee unit siege as default AI and the AI will probably detect that its not much good for that purpsoe and use it less, but you also risk just crashing--I had a unit with boith Worker and Attack AIs and the game crashed whenever an enemy unit was adjacent to one on a tile that needed to be improved because they didn't know what to do). Why not use the Unique Units system in CivilizationInfos? Why you want this capability would dictate the best way to do it.