# Talk:Closed-world assumption

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the table currently hyperlinks items. This is bizarre and confusing to read. The article has nothing to DO with these random links The preceding unsigned comment was added by 66.30.8.51 (talk • contribs) 03:38, 22 December 2005 (UTC)

## Merge with OWA

I would suggest to somehow merge the contents of this and the Open World Assumption article. They ought to explain essentially the two ends of the same concept. Or, in other words, you can not explain one without explaining the other, so that both articles would most likely end up looking like mirror images of each other. However I can not think of a proper way of doing so (redirecting one article to the other doesn't seem 'fair'). There should be examples of similar situations elsewere in Wikipedia, does anybody know about such examples? What has been previously done in such cases? --NavarroJ 11:42, 18 July 2006 (UTC)

While they intuitively are closely related, CWA is technically a form of Non-monotonic logic, while OWA seems to be mostly studied in ontology languages. I'd rather keep them separated for now, and see how these two articles evolve. The downside of merging is that the merged article is likely to evolve in two separate and mostly independent parts (Liberatore, 2006). 11:53, 18 July 2006 (UTC)

Bold text

## Criticism of formula

The following criticism was written directly into the text of the article by HassanAitKaci (talk):

Alternative formalizations not suffering from this problem have been proposed. In the following description, the considered knowledge base ${\displaystyle K}$ is assumed to be propositional. In all cases, the formalization of the closed world assumption is based on adding to ${\displaystyle K}$ the negation of the formulae that are “free for negation” for ${\displaystyle K}$, i.e., the formulae that can be assumed to be false. In other words, the closed world assumption applied to a propositional formula ${\displaystyle K}$ generates the formula:

${\displaystyle K\wedge \{\neg f~|~f\in F\}}$.
• NOTE FROM PUZZLED READER: The above formal statement makes no logical sense since it conjoins ${\displaystyle K}$ with the negations of all the propositions that are in ${\displaystyle K}$ - which is always inconsistent! Shouldn't it rather be: ${\displaystyle K\wedge \{\neg f~|~f\not \in F\}}$?

--LukasMatt (talk) 12:44, 25 May 2014 (UTC)

"(...) the formalization of the closed world assumption is based on adding to ${\displaystyle K}$ (...)"

Since:

1. we are adding to ${\displaystyle K}$, and,
2. ${\displaystyle K}$ denotes a formal language, and, therefore, represents a set:

the composition of the formula should be denoted with a ${\displaystyle \cup }$ (union) as opposed to the current ${\displaystyle \land }$ (logical and), i.e.,

${\displaystyle K\cup \{\neg f~|~f\in F\}}$

--Plbt5 (talk) 13:09, 9 May 2017 (UTC)

## Definition

The closed-world assumption (CWA), in a formal system of logic used for knowledge representation, is the presumption that a statement that is true is also known to be true.

I do not find it logically convincing that an "assumption" is defined as a "presumption". An assumption and a presumption are two different things, see for instance:

http://www.vocabulary.com/articles/chooseyourwords/assume-presume/

I think presumption in that sentence should be replaced by assumption.

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## Example is terrible

Does anyone else think the table is among the worst? Why does the example reference the subject of the page? That's confusing to the reader. The whole "example" section is a disaster. --142.105.196.254 (talk) 15:20, 7 January 2017 (UTC)