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Re: Schema Substitutability Is Transitive?

• From: Ramesh Gupta <ramesh@e...>
• Date: Wed, 11 Oct 2000 14:40:47 -0700

on 10/11/00 2:45 PM, Clark C. Evans at cce@c... wrote:

>> If both <B> and <C> are equivalent to <A> (for substitution),
>> then are they also equivalent to each other? In other words,
>> can <B> be substituted anywhere <C> may occur (without using xsi:type)?
> 
> Transitivity (of substitution):  If A is substitutable for
> B and if B is substitutable for C, then A is substitutable
> for C.  In other words, A > B and B > C implies A > C.
> 
> In your example, you have  B > A  and C > A.
> This does not imply that  B > C or that C > B.
> 

My question was that if B <=> A and C <=> A, then is B <=> C (where <=>
means "equivalent")?

In reality, a substitution group does not define bi-directional equivalence.
So the question becomes "If B => A and C => A, then does B => C?" Of course,
the answer is no, not automatically.

I guess, my question should have been "Is there a way to declare an element
equivalent to more than one other element?" Thanks to Henry for a short and
succinct answer.

Ramesh

• References:
  • Re: Schema Substitutability Is Transitive?
    • From: "Clark C. Evans" <cce@c...>

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