[classad-users] Constraint Question

[Matthew Farrellee <matt@xxxxxxxxxxx>]

ad1 = [A=1]
ad2 = [A=2; B=3]
ad3 = [A=4; C=5]

It's possible to create a constraint that matches ad1 but not ad2: A=! 
=UNDEF && B==UNDEF, right?
What about a constraint matching ads that have only an A attribute.  
Can I do that without knowing about all possible attributes that  
might be in an ad?
Best,


matt