Example

In predicate calculus

	green(fonzie)
	green(puff)
	green(martian)

	dragon(godzilla)
	dragon(puff)

The corresponding translation in Prolog will be :

fly(X) :-	
	green(X),
	dragon(X).

body antecedents that must be true.

A Logical Deduction is called a Query

• Asking for Confirmation
  
  Q : fly(puff)
  A : yes
  
  Q : fly(fonzie)
  A : no
  
  Q : fly(kermit)
  A : no (no unproven, not false
  
  
• Asking for values
  
  Q : fly(X)
  A : X = puff
  
  
  Q : dragon(X)
  A : X = godzilla
  X = puff
  

Find a fact to match the goal : Binding

Some Prolog Facts :

Find a fact to match the goal : Binding

So in the previous example, for instance, puff was found to be a valid answer. If more than one possible answers existed to the problem, then the first goal variable is unbound (i.e. its value discarded) and the next matching value bound to it.

• Matching of goals to facts
• Searching for solutions

Fundamental processes in the understanding of how Prolog works.