A rule is known as ground if all of its atoms (head and system) are floor. A ground rule R1 is actually a ground instance of A different rule R2 if R1 is the results of a substitution of constants for all of the variables in R2. The Herbrand base https://keeganeeysk.thezenweb.com/helping-the-others-realize-the-advantages-of-datalog-71867180