Abstract
As a form of knowledge acquisition from data, we consider the problem of deciding whether there exists an extension of a partially defined Boolean function with missing data \documentclass[12pt]{minimal}
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$$(\tilde T,\tilde F)$$
\end{document}, where \documentclass[12pt]{minimal}
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$$\tilde T$$
\end{document} (resp., \documentclass[12pt]{minimal}
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$$\tilde F$$
\end{document}) is a set of positive (resp., negative) examples. Here, “*” denotes a missing bit in the data, and it is assumed that \documentclass[12pt]{minimal}
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$$\tilde T \subseteq$$
\end{document} {0,1,*}n and \documentclass[12pt]{minimal}
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$$\tilde F \subseteq$$
\end{document} {0,1,*}n hold. A Boolean function f: {0,1}n → {0,1} is an extension of \documentclass[12pt]{minimal}
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$$(\tilde T,\tilde F)$$
\end{document} if it is true (resp., false) for the Boolean vectors corresponding to positive (resp., negative) examples; more precisely, we define three types of extensions called consistent, robust and most robust, depending upon how to deal with missing bits. We then provide polynomial time algorithms or prove their NP-hardness for the problems under various restrictions.