first go to the folder that the database is located (the *.pl files)

to load the database use [*] where star is the name of the database

###############################################################################################################################
#from here on it's Jamies code# 
###############################################################################################################################
#this is only applicable using the database that Jamie has used during his lecture. in this case its lecture 16 [l16] database#
###############################################################################################################################

wet(water).
#returns true

wet(milk).
#returns true

wet(bycicle_lubricant).
#returns false

#prolog has a database in memory and searches the database for assertions that user inputs#

wet(X).
#prolog searches the database for possible instanciations of X which would provide "true" output
#everything starting with a capital letter is a variable
#everything starting with a lowercase letter is a constant

wet(x).
#would output "water". it will find the first hit in the database
#if the user presses "y" then prolog assumes that the instanciation is correct and comes to a halt.
#if the user presses "n" then prolog will produce next possible instanciation and wait for input unless its the last item in the database.
#as long as "n" keeps being pressed during the instanciations, the program will run.

mother(X, ann).
#returns betty

mother(delia, Y).
#returns betty (again)

father(X,Y).
#returns instanciations of X and Y which would provide true for both
#X = chris, Y = ann; (first time, press "n")
#X = eric, Y = betty; (no other possibilities, program comes to a stop)
#not possible to input only 1 variable

mother(betty, _).
#instructs prolog to search the database for anything containing "betty" as first input and returns true if such exists.

mother(X, _).
#returns instanciation of X where X would be a mother of a child (does not require child input)

mother(_, _).
#corresponds to "is someone a mother of someone"
#would require the "n" or "y" input from user if there is more than one possibility
#would return only true if exists
#if it doesnt exist, then returns and error of "Undefined procedure"

parent(betty, jane).
#returns true, because betty is mother of jane

parent(X,Y).
#returns all possible instanciations of both mother(X,Y) and parent(X,Y).

parent(chris, ann).
#returns true (this particular function was used to explain how parent function works (watch the lecture video for explanation at 40:00))