Reification (knowledge representation)
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Reification in knowledge representation is sometimes used to represent facts that must then be manipulated in some way; for example, to compare logical assertions from different witnesses to determine their credibility.
The message "John is six feet tall" is an assertion of truth that commits the speaker to the fact, whereas the reified statement, "Mary reports that John is six feet tall" defers this commitment to Mary. In this way, the statements can be incompatible without creating contradictions in reasoning. For example the statements "John is six feet tall" and "John is five feet tall" are incompatible with each other; the statements "Mary reports that John is six feet tall," and "Paul reports that John is five feet tall," are not incompatible with each other, since they are both compatible with the assumption that either Mary or Paul is incorrect.