tab question

what does it mean when a note in a tab is in parenthesis? does it mean that you don't play it? for example:

h= hammer on
p= pull off

9p7 (7)h9

so after the pull off from the 9 to the 7, would i just hold the 7, that was played in the pull off, without picking it and hammer onto the 9?

right there, it would just mean to hammer onto the 9th fret from the 7th.

it could even mean that you just hammer on without picking, but its probably not that.

ok, thanks.
i got the tab off of a magazine for the "paranoid" solo by black sabbath. it's the very beginning of the solo. and it's written out:

^=bend
h=hammer on
p=pull off
~= vibrato

9^p7 (7)h9~(9)~

i listened to the solo and it sounds like iommi is bending the 9,pulling off to the 7... and then for the (7), he's just holding the previous 7 from the pull off and not picking it again. and then he hammers on to the 9 and vibratos, and for the (9), he just continues to hold that same 9. it sounds like in the solo, the notes in parenthesis mean that they aren't played again....and are just tied notes, or slurred notes from the note right before them. not really sure though...could someone who has heard this solo before tell me if i'm interpreting correctly?

sometimes (#) means it's optional to hit, but i'm not sure if is the same in this circumstance.