\If{$s_t = \emptyset$}\r
\State $MS_s[id_s] = s_s$ \Comment{First occurrence}\r
\Else\r
+ \If{$id_s = id_{self}$}\r
+ \If{$s_t \neq s_s$}\Comment{Check for mismatch on $s$}\r
+ \State \Call{Error}{'Mismatch on $s$ for $id_{self}$'}\r
+ \EndIf\r
+ \Else\r
+ \If{$s_t > s_s$}\Comment{Check for rollback on $s$}\r
+ \State \Call{Error}{'Rollback on $s$ for $id_s$'}\r
+ \EndIf\r
+ \EndIf\r
\State $MS_S[id_s] \gets max(s_t, s_s)$\r
\EndIf\r
\State \Return{$MS_s$}\r