- From: Pat Hayes <phayes@ihmc.us>
- Date: Sun, 28 Feb 2016 00:18:37 -0600
- To: Reto Gmür <reto@wymiwyg.com>
- Cc: "Peter F. Patel-Schneider" <pfpschneider@gmail.com>, semantic-web@w3.org
On Feb 26, 2016, at 3:52 AM, Reto Gmür <reto@wymiwyg.com> wrote: > > > On Thu, Feb 25, 2016, at 06:18, Pat Hayes wrote: >> >> On Feb 23, 2016, at 10:24 AM, Reto Gmür <reto@wymiwyg.com> wrote: >> >>> On Tue, Feb 23, 2016, at 17:05, Peter F. Patel-Schneider wrote: >>>> On 02/23/2016 07:31 AM, Reto Gmür wrote: >>>>> [...] >>>>> >>>>> Granted, the semantics of :rangeIncludes are very weak (under OWA) but >>>>> the fact that you can create contradictions with it shows that it's not >>>>> completely meaningless. >>>>> >>>>> ex:prop1 s:rangeIncludes :Cat . >>>>> :Cat owl:disjointWith :Dog . >>>>> ex:prop1 owl:range :Dog . >>>>> >>>>> The above graph evaluates to false in every possible world, this is not >>>>> the case if you omit any of the 3 triples, this shows that >>>>> `s:rangeIncludes` is not a meaningless decoration. >>>>> >>>>> Reto >>>> >>>> I don't think that this follows from the semantics of :rangeIncludes, >>>> even if >>>> you augment schema.org semantics with disjointness. >>> >>> In the example I also used "owl:range" to create what I thought is a >>> contradiction. >>>> >>>> Perhaps one could also count the documentation of >>>> rangeIncludes as authoritative as well. So from >>>> https://schema.org/rangeIncludes, rangeIncludes "[r]elates a property to >>>> a >>>> class that constitutes (one of) the expected type(s) for values of the >>>> property" would also be part of the semantics of schema.org ranges. >>> >>> I considered only this definition. And based on that I still think there >>> is a contradiction, if the owl:range of a property excludes :Cat (which >>> is expressed with the statements using owl-properties), :Cat cannot at >>> the same time "be (one of) the expected type(s) for values of the >>> property". >> >> Of course it can. It only follows that the values of this particular >> property are all in some other part of the range. According to the >> schema.org definition of rangeIncludes, this is quite permissible. > > I'm not getting you. > > from > > (1) :Cat owl:disjointWith :Dog . > (2) ex:prop1 rdfs:range :Dog . > > It follows that: (3) "no value of the property ex:prop1 can be an of > type :Cat". > > Do we agree till here? Yes. > (4) ex:prop1 s:rangeIncludes :Cat > > means: (5) "The class :Cat is an expected type for values of the > property ex:prop1" I do not know what this means. What defines something as an 'expected type'? > Do you agree that (5) follows from (4) when using the definition from > http://schema.org/rangeIncludes? As I say, I have no idea. I can make guesses, but the text given to explain http://schema.org/rangeIncludes is not precise enough to determine any entailments. It must remain so until someone gives a model-theoretic definition of what "expected" means. > > Agreeing to both (4) and (5) boils down to: > > - :cat is an impossible type for values of the property ex:prop1 > - :cat is an expected type for values of the property ex:prop1 > > Using the first definition of "Expect" from the oxford dictionary as > "Regard (something) as likely to happen", I think there is a > contradiction between asserting that something is impossible and that > something is expected. I do not. It might be irrational to expect an impossibility, but it is not a logical contradiction. This seems particularly the case when the expectation can be weakened by providing an alternative expectation, as is apparently the intended meaning of the Schema wording here. If I am given two (or more) expectations with the understanding that I am obliged only to expect their disjunction, and if one of them turns out to be impossible, then this impossibility merely strengthens my expectation for the other one (or ones.) And even when I am provided only with one expectation, I am surely free to imagine that others might be possible, and even that I might soon find out about them. > I would really like to learn where you think my reasoning is wrong. I would like to see your reasoning formalized before setting out to find the exact error in it, but I do not accept your conclusion given what you have said so far. Best wishes Pat > > Cheers, > Reto > >> If you disagree, please suggest how to express the schema semantics as a >> precise model-theoretic condition in such a way that it produces the >> contradiction you expect. >> >> Pat Hayes >> >>> >>> Reto >>> >>> >>> >> >> ------------------------------------------------------------ >> IHMC (850)434 8903 home >> 40 South Alcaniz St. (850)202 4416 office >> Pensacola (850)202 4440 fax >> FL 32502 (850)291 0667 mobile (preferred) >> phayes@ihmc.us http://www.ihmc.us/users/phayes >> >> >> >> >> >> > > ------------------------------------------------------------ IHMC (850)434 8903 home 40 South Alcaniz St. (850)202 4416 office Pensacola (850)202 4440 fax FL 32502 (850)291 0667 mobile (preferred) phayes@ihmc.us http://www.ihmc.us/users/phayes
Received on Sunday, 28 February 2016 06:19:11 UTC