lue into the slot value. Precisely, if both an old value and a new 
value are not a list and different from each other, the result of adding is a 
list of old and new value. If both are a list, the result is a union of both. If 
one of them is not a list, it is added (adjoin) to another value as a set 
element. This is from the monotonicity principle in Semantic Webs.</p>
<code>gx-user(17): (defIndividual MyResource (myProp "original 
one"))<br/>Warning: Entail by rdf1: myProp rdf:type 
rdf:Property.<br/>#&