Challenge Nov-2014

Decision Model “Who killed Agatha?” Solutions

Someone in Dreadsbury Mansion killed Aunt Agatha. Agatha, the butler, and Charles live in Dreadsbury Mansion, and are the only ones to live there. A killer always hates, and is no richer than his victim. Charles hates noone that Agatha hates. Agatha hates everybody except the butler. The butler hates everyone not richer than Aunt Agatha. The butler hates everyone whom Agatha hates. Noone hates everyone. Who killed Agatha?

Proposed by: Len Schubert. This is problem #55 of [Pelletier, 1986].

Useful hints can be found here. Send your solutions to DecisionManagementCommunity@gmail.com.

Solutions:

  • IBM ODM – submitted by Charo Álvarez from DECIDE.  Unfortunately Charo came to an invalid conclusion: “We have solved the mystery … Charles is the killer.” You do not need any tool to quickly conclude why this is wrong:
        1. Agatha hates everybody except the butler => Agatha hates herself
        2. Charles hates noone that Agatha hates => Charles does not hate Agatha
        3. A killer always hates his victim => Charles is not a killer

In real-world decision modeling people make mistakes even more often but unfortunately it is not so simple to notice them. Hopefully the author will be able to fix his model.

Dec 2, 2014. We received the following email from Charo Alvarez:  “Sorry for the confusion. With this statement, ‘A killer always hates, and is no richer than his victim’ , I understood that the killer always hates, someone, not necessarily the victim. I fix the error simply by modifying a rule. I have post how i fix it.”

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