Damage calculation and weapons

First of all, sorry if the question has already been asked before, but I couldn't find it (and while we're at it, sorry for my english too).


I just wonder how the affix "increased [damage type] " work on weapon.
Does it directly increases the damage of the weapon, and so is multiplicative with the rest of our damage modifiers, or is it just another damage modifier wich add to the others ?
I know it says "increased" and not "more" so it's additive, but it also directly modify the damage range on the weapon tooltip, so I'm not sure.

And, if it is the first case (if it's the second the question sorta answers itself), how work the passives "increased [damage type] damage with [weapon type]" ?
Is it just another increased damage who take effect only when we use a weapon of this type (as i was thinking before the first question occur to me), and work if the damage type is absent on the weapon but is caused by a skill/support ; or does it modify the damage of the weapon and is multiplicative with other modifiers, but prevent the modification of the damage if it is only caused by a skill ?

It's a global increase, similar to things on the tree.

Okay, thanks for the reply.

EDIT : after testing (and a couple of alts wasted), I'm sure this is not exactly the case.
Elemental increases of weapons implicits are effectively another damage increase wich add to other increases, but the local affix "increased physical damage" on weapons is definitely multiplicative with all other increases.
Wich is a bit strange by the way, as the wording don't differs from elemental ID. The only clue is the changed and blue damage range on the weapon.