Help understanding this SVA syntax

In reply to ben@SystemVerilog.us:

Sorry, but I still do not understand… I am not worried about the correctness of the expression.

(1, data = !d_in)

Is this some sort of concatenation? Or some kind of a conditional statement for assertions? What does ‘1’ do here? data is being assigned !d_in which makes sense to me. But I dont see how ‘1’ fits in here…