效绵鼎 Conventions ■ a,b,..are input symbols. 0 But sometimes we allow e as a possible value. ■.，X,Y,Z are stack symbols. ...w,X,y,z are strings of input symbols. a,B,...are strings of stack symbols. 7Conventions ◼ a, b, … are input symbols.  But sometimes we allow ε as a possible value. ◼ …, X, Y, Z are stack symbols. ◼ …, w, x, y, z are strings of input symbols. ◼ , ,… are strings of stack symbols. 7