# Entailment

For people who would rather read FormalSystemsLanguage:

"Formula Fentailsformula G if every interpretation that satisfies F also satisfies G."

For the rest of us, and in particular, those of us interested in RDF and the SemanticWeb:

A graphentailsanother graph, when anything you can learn from the first graph, it won't contradict anything learnable from the second graph.

For example, suppose you had *one* graph, that said:

- Jane is a girl.
- Jane is 21.
- Jane has blond hair.

And then we had a *second* graph, that said:

- Jane is a girl.

We can say here that the first graph entails the second. That's because from everything you understand from the first graph, there is no contradiction in the second graph.

It's important to note that this isn't just what's *said,* but anything that you can *come to understand* from it, as well.

For instance, *this graph...*

- A cat is an animal.
- There is a cat.
- Anything of the form "X exists", "X is a Y," you can also say: "Y exists."

...entails *this graph...*

- There is a cat.
- There is an animal.

That's because, anything you could learn from the first one, it won't be contradicted by the second one.

## See also

"Following conventional terminology, I satisfies E if I(E)=true, and a set S of RDF graphs (simply) entails a graph E if every interpretation which satisfies every member of S also satisfies E."

- entailment section of the RDF specification

# Discussion

Well, I gave it a go. This is the best I can come up with.

If it's wrong, but 95% correct, that's good enough for me.

If there are major cases where my understanding and explanation are flawed, feel free to point out the some examples of offending situations, and we can rework the text.

-- LionKimbro DateTime(2004-10-17T09:57:08Z)

Wow... you're a quick study. -- DanConnolly