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Transitive implication in a subtype graph

Last post Sat, Mar 28 2015 14:00 by Terry Halpin. 1 replies.
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  • Sat, Mar 28 2015 11:52

    Transitive implication in a subtype graph

    In NORMA, suppose I create three object types (A, B, C) and declare that:

    • A is a subtype of B
    • B is a subtype of C
    • A is a subtype of C
    In this situation, NORMA reports an error message stating that "Direct supertypes...must be overlapping without transitive implication."  Why does transitive implication warrant an error message?  I understand that the subtype relationship from A to C is redundant given that A is also a subtype of B, but does transitive implication cause some other semantic problem besides redundancy?
      
    Matt 

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  • Sat, Mar 28 2015 14:00 In reply to

    Re: Transitive implication in a subtype graph

     Subtyping in ORM is always direct subtyping, not indirect subtyping. Direct subtyping is strongly intransitive, so transitively implied subtyping relationships should not be asserted.

     

    Cheers

    Terry 

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