Here's a breakdown of the StarbaseModules.xml tags.
[StarbaseModule InternalName=""] : InternalName is the unique identifier. It's used for Module_Requirement.
[Name] : Name shown ingame.
[Model] : Not Used. The 4 types of starbases use shipcfg files for starting and upgraded models.
[Description] : Not Used. The description you see ingame is based on what the module does.
[Tech_Requirement] : The tech you need to research before the module is available. Doesn't support multiple requirements.
[Module_Requirement] : The module needed on the starbase before this module can be added. Doesn't support multiple requirements.
[ModuleSize] : Not used.
[ModuleCost] : BC cost to add module to startbase.
[Type] : There are 5 different types:
Defense - The module can be added to any starbase.
Military - The module can only be added to Military Starbases
Culture - The module can only be added to Influence Starbases
Economy - The module can only be added to Economic Starbases
Mining - The module can only be added to Resource Starbases
[StarbaseAbility] : This determines what the module does. Each ability has associated tags with it. Using tags from a different ability yeilds undesired results. Attack and Defense can not be on the same module for this reason.
StarbaseAttack : Increases Attack of Starbase
AttackAssist : Increases Attack of Ships in range of Starbase
AttMassDriver - Value of Mass Driver attack added
AttMissile - Value of Missile attack added
AttBeam - Value of Beam attack added
StarbaseDefense : Increases Defense of Starbase
DefenseAssist : Increases Defense of Ships in range of Starbase
DefArmor - Value of Mass Driver defense added
DefPointDefense - Value of Missile defense added
DefShields - Value of Beam defense added
Culture : Adds to Culture ability
ProductionAssist : Adds to Military Production, Social Production, and Research of planets in range
Mining : Adds to the ability of the type of resource being mined
Trade : Adds to traderoute income (the specifics are still debated)
StarbaseAbilityValue - The value added
SpeedAssist : Adds movement to your own ships starting their turn in range of the Starbase
SlowEnemies : Removes movement of ships starting their turn in range of the Starbase. This value should be Negative!
StarbaseAbilityValue - This is the actual number of moves given/taken (1 for 1 movement instead of 10 speed skill).
StarbaseSensors : Adds to the sensor range of the Starbase
SensorRange - Number of parsecs added
Please post any errors I may have made, or bugs you come across.
Feel free to reorganize this data and add it to the wiki! While a little credit for it may be nice (originally by Syneris, fixed edited updated etc by...), it's not necessary as long as it gets added on the wiki to help people who may want it