If you are learning about the Semantic Web, one of the things you will hear is that the Semantic Web assumes the Open World. In this post, I will clarify the distinction between the Open World Assumption and the Closed World Assumption.
The Closed World Assumption (CWA) is the assumption that what is not known to be true must be false.
The Open World Assumption (OWA) is the opposite. In other words, it is the assumption that what is not known to be true is simply unknown.
Consider the following statement: “Juan is a citizen of the USA.” Now, what if we were to ask “Is Juan a citizen of Colombia?” Under a CWA, the answer is no. Under the OWA, it is I don’t know.
When do CWA and OWA apply?