<html><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; "><div>(Sorry for the late reply. My ISP has been blocking outgoing email. Only solved it today with an SSH tunnel.)</div><br><div><div>* Robert Barta</div><blockquote type="cite"><div><br>To be precise, the current draft says this:<br><br> The isa relationship is non-reflexive, i.e. x isa x for no x \elem<br> m, so that no proxy can be an instance of itself.<br><br>That is not the same as saying "the isa relation is not reflexive".</div></blockquote><div><br></div><div>True. I was being imprecise. Let me try again.</div><div><br></div><div>The problem is that the current draft says:</div><div><br></div><div><blockquote type="cite"><font class="Apple-style-span" color="#000000">The isa relationship is non-reflexive, i.e. x isa x for no x \elem<br>m, so that no proxy can be an instance of itself.</font></blockquote><br></div><div>Whereas we really have a case where a topic is an instance of itself.</div><div><br></div><div>Could we live without it? Yes, I guess we could, but it would cause some difficulties, because we need to write a TMCL schema for TMCL, which will be used to verify that TMCL schemas are structured correctly. At least I think it would.<br></div><br><blockquote type="cite"><div>If we assume that isa models an instance/class relationship,<br>then writing<br><br> x isa x<br><br>means that a class is an instance of itself. </div></blockquote><div><br></div><div>Yes, it does.</div><br><blockquote type="cite"><div>I have no idea what that means and [...]</div></blockquote><div><br></div><div>The topic type of all topic types is a topic type, and so an instance of itself. Whether we allow this to be said or not is a different issue, but semantically there is no doubt that it is an instance of itself.</div><div><br></div><div>Similarly, tmdm:subject is the type of *everything*, and therefore also an instance of itself. There's nothing that isn't a subject, so it must be a subject.</div><br><blockquote type="cite"><div>I am definitely too uneducated[1] to understand the consequences of making isa reflexive for *every* thing. </div></blockquote><div><br></div><div>So am I. That would be crazy.</div><div><br></div><div>No, what we want is to be able to have some very few types be able to do this.</div><br><blockquote type="cite"><div>Is this really the same 'isa'? What _exactly_ are you trying to<br>express with it?</div></blockquote><div><br></div><div>Well, in TMQL we have wired the two together, so clearly we do think it is the same 'isa', and it would be a pretty messed up TMDM->TMRM mapping that didn't use this machinery.</div><div><br></div><blockquote type="cite"><div><span class="Apple-style-span" style="-webkit-text-stroke-width: -1; ">What I understand what you suggest is to drop the TMRM constraint "isa</span></div></blockquote><blockquote type="cite"><div>is non-reflexive", allowing someone to write x isa x.</div></blockquote><div><br></div><div>Yes.</div><div><br></div><div>For two reasons:</div><div><br></div><div> (1) We have use cases for it.</div><div><br></div><div> (2) The TMRM aims to be a universal data model with no ontological</div><div> commitments whatever.</div><div><br></div><div>Given the latter, isn't it a bit hard to defend this restriction? After all, I'm sure there are systems where isa can be reflexive. For example, RDF: <a href="http://www.w3.org/TR/rdf-schema/#ch_class">http://www.w3.org/TR/rdf-schema/#ch_class</a></div><div><br></div><div>How universal is the TMRM really if it cannot support all of TMDM and RDF?</div><div><br></div><div><blockquote type="cite">From where I am sitting, I cannot say what the impact on TMRM<br></blockquote></div><blockquote type="cite"><div>semantics (or the mapping would be).</div></blockquote></div><div><br></div><div>Maybe we should work that out, then. </div><br><div> <div><div>--Lars M.</div><div><a href="http://www.garshol.priv.no/blog/">http://www.garshol.priv.no/blog/</a></div><div><a href="http://www.garshol.priv.no/tmphoto/">http://www.garshol.priv.no/tmphoto/</a></div><div><br></div></div><br> </div><br></body></html>