From: Jesse Weaver <weavej3@rpi.edu>

Date: Thu, 6 Sep 2012 16:13:28 -0400

Message-Id: <24A1E9A9-3735-44E4-B0AA-1D2CAB5DDF81@rpi.edu>

To: Christian De Sainte Marie <csma@fr.ibm.com>

Cc: public-rif-comments@w3.org

Date: Thu, 6 Sep 2012 16:13:28 -0400

Message-Id: <24A1E9A9-3735-44E4-B0AA-1D2CAB5DDF81@rpi.edu>

To: Christian De Sainte Marie <csma@fr.ibm.com>

Cc: public-rif-comments@w3.org

Hi Christian. I have occasionally been checking on the erratum for RIF-PRD. I still have some concerns about erratum 16.2. If these concerns are unfounded, please let me know where my misunderstanding lies. If I have overlooked available answers to my questions, please direct me toward them. The proposed solution to http://www.w3.org/2005/rules/wiki/Errata#Erratum_16.2 is to add the following condition in the definition of State of the Fact Base (SFB): "for every equality term t1=t2 in \Phi, if t1 and t2 are, both, constants in the symbol spaces that are data types, then they have the same value;". This seems like a partial solution, since it applies only to cases in which t1 and t2 are constants in symbol spaces that are data types. What if the equality statement has a term that is not a constant (like a list), or a constant that is not in the symbol space of a data type? Should such facts be allowed in a SFB? If so, shouldn't there be more conditions on SFB to ensure symmetry and transitivity of equality? For example, the new condition basically says that explicit facts in a SFB pertaining to equality of "datatyped" constants must agree with how these equality statements would be evaluated independent of the SFB. So one can no longer say that 1=2. However, one could still form the following SFB: 1=_x 2=_x _x=:iri_representing_1 2=:iri_representing_2 3=List() There appear to be a few problems here. Using the new definition of matching substitution from http://www.w3.org/2005/rules/wiki/Errata#Erratum_16.3 , 1. Effective equality of unequal constants. And(1=?v ?v=2) matches the SFB, but 1=2 does not. 2. Effective inequality of equal constants by lack of transitivity. And(1=?v ?v=:iri_representing_1) matches the SFB, but 1=:iri_representing_1 does not. 3. Effective inequality of equal constants by lack of symmetry. 2=:iri_representing_2 matches the SFB, but :iri_representing_2=2 does not. 4. Non-intuitive equality. 3=List() matches the SFB, but should not. The first three conflict with the model-theoretic semantics which interpret equality statements as logical equality, and thus symmetry and transitivity should apply. In general, all of them seem to conflict with basic intuition. Jesse Weaver Ph.D. Student, Patroon Fellow Tetherless World Constellation Rensselaer Polytechnic Institute http://www.cs.rpi.edu/~weavej3/index.xhtmlReceived on Thursday, 6 September 2012 20:13:59 UTC

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