I am studying Pseudorandom Number Generators and when reading the discussion on One-Way Functions and Hardcore Predicates, I came upon this equation.
I understand that the $b(x,r)$ is the hardcore predicate (either a $1$ or $0$) but I do not understand the operation being performed here. Specifically, I have never before seen the XOR symbol ($\oplus$) used in this way and do not understand what it signifies. Is it the sum of the values found by XORing $x_j$ and $r_j$? $\bmod 2$?