when using the entitydata command to add an atribute to an item on the ground i used this command by the way:
/entitydata @e[type=Item,c=1] {Item:{tag:{AttributeModifiers:[{AttributeName:"generic.maxHealth",Name:"generic.maxHealth",Amount:20,Operation:0,UUIDLeast:941137,UUIDMost:134331}]}}}
it will reset the items atributtes such as attack speed and armor values on that item
The existence of the
AttributeModifiers
list prompts default modifiers to be ignored. You must re-add them yourself.EDIT: To explain why this is a good thing: if a default modifier used an operation of 1 or 2, then map makers could not easily use
AttributeModifiers
to balance certain items if the default modifiers remained on the items.