[openbox] Application matching on name, role, class, type

[Eric Bohlman]

(Reason for the questions is that I'm writing a graphical tool for 
Openbox application settings)

Is there any difference between omitting an attribute on an 
<application> tag and setting it blank? e.g. does role="" match any 
role, or only a window without a role set?

Also, it's mentioned that <position> is honored only if both x and y are 
set. Does this also apply to the <monitor> sub-element (i.e. can you 
specify a window's monitor without putting it at particular coordinates)?

Finally, there's an error on the help:applications page: it mentions 
_OB_APP_TITLE instead of _OB_APP_ROLE.