(deftemplate person "the person template"
    (slot name)
    (slot blood)
)

(deftemplate blood "the blood type template"
    (slot kind)
    (slot is-compatible-with)
    (slot not-compatible)
)
    
(deffacts blood-bank-clients
    (person (name John)(blood O))
    (person (name Paul)(blood A))
    (person (name George)(blood B))
    (person (name Ringo)(blood AB))
    (blood (kind O) (is-compatible-with O) 
        (kind O)(not-compatible A)
        (kind O)(not-compatible B)
        (kind O)(not-compatible AB) )
    (blood (kind A) (is-compatible-with O)
    (kind O)(is-compatible-with A)
            (kind A)(not-compatible B)
            (kind A)(not-compatible AB) )
    (blood (kind B) (is-compatible-with O)
    (kind B)(is-compatible-with B)
            (kind B)(not-compatible A)
            (kind B)(not-compatible AB) )
    (blood (kind AB) (is-compatible-with O)
    (kind AB)(is-compatible-with A)
    (kind AB)(is-compatible-with B)
    (kind AB)(is-compatible-with AB) )
)

(defrule compatible
        (person (name ?person1) (blood ?kind1))
        (person (name ?person2) (blood ?kind2))
        (blood (kind ?kind1) (is-compatible-with ?kind2))
        =>
        (assert (compatible ?person1 ?person2))
)

(defrule match
         (compatible ?person1 ?person2)
         (compatible ?person2 ?person1)
         (test (neq ?person1 ?person2))
         =>
         (printout t " is compatible with " ?person1 " to " ?person2 crlf) 
)