What does the operation integer in AttributeModifier represent? I'm guessing that it's a mathematical operation done to a number, but what integers represent what operation?

the integer param represents the operation type

 

0==additive

1==additive multiplicative

2==direct multiplicative

 

 

orignal value = x;

modifier value = y;

modified value = z;

 

additive:

z = x+y;

additive multiplicative:

z = x + x*y;

direct multiplicative

z= x * (1+y)

 

-- http://minecraft.gamepedia.com/Attribute