entailment

Entailment means that a sentence is true belonging to a true Knowledge base. It is said that the sentence entailed from the knowledge base.

It is denoted as where KB is knowledge base which is true and α is a sentence.

KB ⊨ α

So, above statement says that KB entails α.

When a sentence is entailed from a true knowledge base, then the sentence is said to be true.

In more logical terms, an formula $f$ is entailed from the $KB$ then the following is true.

$$M(KB)\subseteq M(f)$$

Entailed $f$ is not adding any new information to the $KB$. For example,

$KB=\{Rain\wedge Wet\}$ $f=Rain$

then, $M(KB)=\{(Rain:true,Wet:true)\}$ $M(f)=\{Rain:true\}$

So, $M(KB)\subseteq M(f)$

We can say that $KB\models f$.