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Thread: FOL question

  1. #1
    Newbie
    Joined
    Nov 2008
    Posts
    1

    FOL question

    Could somebody just tell me how to write :

    James is wearing a grey scarf?

    in first order logic?

    Thanks in advance
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  2. #2
    Senior Member
    Joined
    Nov 2008
    From
    Paris
    Posts
    354
    Wow that seems imprecise.. That depends on how you define your properties. For instance, that could be
    1) if $\displaystyle P(x)$ means "$\displaystyle x$ is james" and $\displaystyle Q(x)$ means "$\displaystyle x$ wears a grey scarf", it would be:

    $\displaystyle \forall x P(x) \Rightarrow Q(x)$

    2) If $\displaystyle P(x)$ means "$\displaystyle x$ is james", $\displaystyle Q(x,y)$ means "$\displaystyle x$ wears $\displaystyle y$", $\displaystyle S(x)$ means "$\displaystyle x$ is a scarf" and $\displaystyle G(x)$ means "$\displaystyle x$ is grey", then it would be

    $\displaystyle \forall x P(x) \Rightarrow \exists y ( S(y) \wedge G(y) \wedge Q(x,y) )$
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