Armor Stats

Do armor pieces with things like "Armor + 15 (while Attacking)" or "Armor + 15 (vs. Slashing)" counted only for that particular piece of armor, or overall?

For example if I have a legging with Armor + 15 (vs. Slashing) and whatever is attacking me has slashing damage and hits me in the head, do I get the Armor + 15 bonus or not?

All armor bonuses are local, except for 2.

Knight's/Ascalon damage absorbtion is global. The +X Vs physical is still local.
The Mesmer armor with +X AL while casting is also global.

Note that in both cases, the global effect is non-stacking, so there no point in wearing more than one piece of these armors.