Re: Schema.org and OWL

OK, it appears that you are trying to produce an OWL ontology that would
accept schema.org documents that would accept unexceptional schema.org
documents (under some loose definition of what makes an unexceptional
schema.org document).


But you are running up against problems with "strings as things" and Roles.  


Look at about and subjectOf.   Any use of a string as a value for about is
going to make that string an instance of two OWL Classes (the range of about,
which includes Text, and the domain of subjectOf, which doesn't).  This is not
permissible in OWL.  


Using a role as a value for subjectOf will make the role node an instance of
the domain of about, which doesn't include Role.   Roles fall outside the
purview of OWL. 


What I think has to be done for "strings as things" is to preprocess them as
an anonymous node with the string as the value of some description property. 
Roles need to be short-circuited and the role values eliminated.  If the role
values are to be retained then some sort of fancy reification has to be
introduced.


But a lot of this is guesswork, as it is unclear just what "strings as things"
and Roles mean in schema.org.   (I haven't looked closely at the use of URLs
as stand-ins for objects but my guess is that that is similar to "strings as
things".)



OWL makes a distinction between object and data values, and this distinction
has to be carried through to the ontology, where there are classes and
datatypes.  As far as I can tell Text should be a datatype.




peter



On 06/06/2018 07:09 AM, Richard Wallis wrote:
> Just the fresh pair of experienced eyes I needed! - Thanks @Thomas
>
> @Danbri - not “wasting a lot of time agonising", in simple terms I’m just
> [selfishly] trying to get a useful version to load into Protégé and
> hopefully helping a few others at the same time.  
>
> @Peter thanks for your thoughtful questions.  As you can see from the above
> the prime simple objective is to get it visible in Protégé.  Beyond that, it
> is to capture the class and property hierarchy of Schema.org including
> the multiple domain/ranges of properties defined [In Schema.org] using
> domainIncludes & rangeIncludes, in a way that a tool like Protégé can cope
> with.  As for ranges, it includes the assumption that properties, in
> addition to the defined range(s), also have Text, URL, and Role included in
> their range.
>
> Once I’ve done it, I want to add the simple generating code to the Schema
> scripts run at release time so that it can be kept up to date.
>
>
> ~Richard.
>
> Richard Wallis
> Founder, Data Liberate
> http://dataliberate.com
> Linkedin: http://www.linkedin.com/in/richardwallis
> Twitter: @rjw
>
> On 6 June 2018 at 14:45, Peter F. Patel-Schneider <pfpschneider@gmail.com
> <mailto:pfpschneider@gmail.com>> wrote:
>
>     It's hard to say much about the file without knowing what it is supposed to
>     capture.
>
>
>     It is supposed to capture the class and property hierarchy and property
>     restrictions or schema.org <http://schema.org>, but not necessarily in a
>     form compatible with RDFS
>     or OWL?
>
>
>     Is it supposed to faithfully encode the model theory of schema.org
>     <http://schema.org> in OWL?  
>     If so, where is the document for this theory?
>
>
>     Is it supposed to capture "strings as things" or Roles? 
>
>
>     How does it view property domains and ranges?   As axioms?  As strict
>     constraints?  As soft constraints?
>
>
>     I would also move from rdf/xml to turtle, which is easier to write and
>     easier
>     to read.
>
>
>     peter
>
>
>
>     On 06/06/2018 05:05 AM, Richard Wallis wrote:
>     > Calling folks with more OWL experience than me!
>     >
>     > The schema.org <http://schema.org> <http://schema.org> site has an OWL
>     definition file that has
>     > not been maintained since April 2014: http://schema.org/docs/schemaorg.owl <http://schema.org/docs/schemaorg.owl>.
>     > Also the structure and syntax of the file needs some attention.
>     >
>     > To help with the occasional questions about accessing processable
>     > representations of the vocabulary; to attempt to close an issue (#1611
>     > <https://github.com/schemaorg/schemaorg/issues/1611
>     <https://github.com/schemaorg/schemaorg/issues/1611>>); and to help with a
>     > personal project, I have had a look at producing an up to date, improved,
>     > maintainable version of the file.
>     >
>     > My first attempt can be downloaded/viewed
>     > here: https://s3.amazonaws.com/rjwPublicData/public/schemaorg.owl
>     <https://s3.amazonaws.com/rjwPublicData/public/schemaorg.owl>
>     >
>     > I am looking for comments, suggestions, and help around a few aspects of
>     > this work in progress:
>     >
>     >   * Is it generally ‘a good owl file’
>     >
>     >   * Should it contain more/less info about the vocabulary and its terms
>     >
>     >   * Specifically with reference to domainIncludes and rangeInclude -
>     mapped
>     >     to rdfs:domain & rdfs:range with owl:unionOfcollections:
>     >
>     >       o Is this the best/only way to represent multiple domain &
>     ranges for
>     >         an objectproperty?
>     >
>     >       o Have I got the syntax correct?
>     >
>     >   * Several people use Protégé <https://protege.stanford.edu/> as a
>     tool for
>     >     this kind of effort - I am trying to identify what syntax, will enable
>     >     this tool to recognise the multiple domain/ranges when importing
>     this file.
>     >
>     > If anyone out there with more OWL experience than me (not difficult),
>     could
>     > spend a few minutes taking a look at this and commenting, it would be
>     > greatly appreciated.
>     >
>     > ~Richard 
>     >
>     > Richard Wallis
>     > Founder, Data Liberate
>     > http://dataliberate.com
>     > Linkedin: http://www.linkedin.com/in/richardwallis
>     <http://www.linkedin.com/in/richardwallis>
>     > Twitter: @rjw
>
>
>

Received on Wednesday, 6 June 2018 14:37:32 UTC