A rule is referred to as ground if all of its atoms (head and system) are floor. A ground rule R1 can be a ground occasion of another rule R2 if R1 is the results of a substitution of constants for many of the variables in R2. The Herbrand foundation https://datalog16058.blog-kids.com/34093956/how-much-you-need-to-expect-you-ll-pay-for-a-good-datalog-5