"Same Source" definition for stacking bonuses

[Zombie Lord]

My question relates to the sections on Special Spell Effects and Combining Magic Effects.

Special Spell Effects (PRD Link)

Specifically: "Bonuses without a type always stack, unless they are from the same source."

What is the definition of "Same Source"?

If a bonus is untyped, and they come from different people, are the people the source or is the name of the ability they use the source?

I am looking for a general definition of Same Source that I can apply elsewhere, but I also have these two specific examples:

1. Arcane Subdomain.

2. Eldritch Aid (feat, advanced class origins, couldn't find it in the Piazo PRD)

For either of these, if you have multiple characters providing the same benefit, do they stack?

For example: If you have 100 clerics with the Arcane Subdomain, is each cleric a different source? or is the Arcane Subdomain itself considered the source?

Likewise, if you have 100 casters using the Eldritch Aid feat in the same round, is each caster a different source? or is the Eldritch Aid feat considered the source?

[Maezer]

Its the ability.

[Kazaan]

It would be the ability. To simplify the problem, lets say there's a hypothetical spell that grants a +1 untyped bonus to your attack roll. If two separate casters both cast the spell on you, it would be considered the same source (the spell) and they wouldn't stack. Another example would be the bonus to damage from Power Attack. You couldn't, for instance, say, "I'll use Power Attack twice to get double the damage for double the penalty," because the bonus from the same source (the feat) wouldn't stack (though, the penalty would so, in this case, you'd get double penalty for single bonus damage).

[Darksol the Painbringer]

An in-game example would be if you're receiving an attribute bonus to an effect (Charisma to Saves), the Charisma modifier of your character is the source of the effect, even though it's actually the Class Feature which grants you the Charisma to Saves. It is because of this that if you were to, for example, attempt to get your Charisma to Saves twice, it wouldn't stack.

To me, I believe a source falls under whatever is granting you the bonus. In the above example, although the class feature is enabling you that ability, the attribute you possess is what is granting you the bonus is what is actually the source of the power behind said class feature, which makes that the source.

Now, effects from the same source don't stack, which means that if you were to, for example, cast the Haste spell twice, they won't stack, because the source of the bonuses being granted come from the spell, and not from some other effect which is granting you the bonuses.

That being said, there's no actual definition of same source, and I doubt a FAQ is going to properly clarify what that is, because the definition of "same source" varies from case to case, and from perspective to perspective.

[BigNorseWolf]

Source is the spot where the number comes from, unless it says otherwise with an "X type of bonus equal to " something language.