Re: Proposed Errata 16 (RIF-PRD)

Hi Jesse,

Yes, I had noticed the inconsistency myself, and I corrected it in a 
subsequent version of the errata (see erratum 16.2 [1]).

[1] http://www.w3.org/2005/rules/wiki/Errata#Erratum_16.2

I think that all the reported errors have been corrected, now, and the are 
ready to publish the second edition.

Would you be so kind and check all the errata again, and tell me if you 
find something?

Thanx for your help,

Christian

IBM
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From:   Jesse Weaver <weavej3@rpi.edu>
To:     Christian De Sainte Marie/France/IBM@IBMFR
Cc:     public-rif-comments@w3.org
Date:   14/08/2012 20:17
Subject:        Proposed Errata 16 (RIF-PRD)



Hi Christian.

I was looking over the proposed errata for RIF ( 
http://www.w3.org/2005/rules/wiki/Errata ), and I am quite happy with the 
proposed solution to errata 16.  I think, though, that there is a problem. 
 The proposed operational semantics for equality is stricter than the 
model-theoretic semantics of equality.  For example, as I understand it, 
_a=_b cannot be matched under the operational semantics, but it could be 
true under the model-theoretic semantics as long at I(_a)=I(_b), unless of 
course there is a unique name assumption.  I'm not sure of a good way to 
reconcile the two semantics, but perhaps at least a note should be made 
about the inconsistency if the proposed change to the operational 
semantics is made.

Another possible solution would be to allow matching equality formulas to 
sets of facts, but then there is the problem of redefining State of the 
Fact Base to ensure symmetry and transitivity of equality facts.  It is 
more complicated, but it is consistent with the model-theoretic semantics.

Personally, I like the simplicity of the proposed solution in the errata, 
but I just wanted to point out this potential inconsistency.  Thanks for 
addressing previously reported issues in the errata.

Jesse Weaver
Ph.D. Student, Patroon Fellow
Tetherless World Constellation
Rensselaer Polytechnic Institute
http://www.cs.rpi.edu/~weavej3/index.xhtml



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