Why Protege makes a copy of DatatypeProperty as ObjectProperty

Question

I noticed that Protege creates "copies" properties I created as DatatypeProperty and marks them as ObjectProperty. Which in turn makes them to be both datatype and object property at the same time. I tried to fix it manually in the OWL file. Assigned "xsd:string" as Range. Nothing helps.

Protege reads in the OWL file and shows the property I just fixed on both lists. If I modify anything and it will save the ontology back to the OWL file, two entries will be made.

What is more "funny" my Range specification (to xsd:string) is set to the ObjectProperty entry, not the original Datatype.

Any ideas?

Here is an example.

"Original"

###  http://www.umwd.dolnyslask.pl/ontologies/2014/03/midas#title

:title rdf:type owl:DatatypeProperty ,
               owl:FunctionalProperty ;

      rdfs:label "tytuł"@pl ;

      skos:definition """xxxxxx""" ;

      rdfs:comment """comment"""@pl ;

      rdfs:domain :Annotation ,
                  :Entity .

Copy added by Protege (notice that rdfs:range has been moved to the copy)

###  http://www.umwd.dolnyslask.pl/ontologies/2014/03/midas#title

:title rdf:type owl:ObjectProperty ;

       rdfs:label "tytuł"@pl ;

       skos:definition """xxxxxx""" ;

       rdfs:comment """comment"""@pl ;

       rdfs:range xsd:string .

UPDATE: Here is the minimal ontology which after opening in protege results in problem shown above:

@prefix : <http://my.ontolo.gy/test#> .
@prefix dc: <http://purl.org/dc/elements/1.1/> .
@prefix owl: <http://www.w3.org/2002/07/owl#> .
@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
@prefix xml: <http://www.w3.org/XML/1998/namespace> .
@prefix xsd: <http://www.w3.org/2001/XMLSchema#> .
@prefix bibo: <http://purl.org/ontology/bibo/> .
@prefix foaf: <http://xmlns.com/foaf/0.1/> .
@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
@prefix skos: <http://www.w3.org/2004/02/skos/core#> .
@prefix midas: <http://my.ontolo.gy/test#> .
@prefix vcard: <http://www.w3.org/2006/vcard/ns#> .
@prefix dctype: <http://purl.org/dc/dcmitype/> .
@prefix schema: <http://schema.rdfs.org/all#> .
@prefix dbpedia: <http://dbpedia.org/ontology/> .
@prefix dcterms: <http://purl.org/dc/terms/> .
@prefix location: <http://www.w3.org/ns/locn#> .
@base <http://my.ontolo.gy/test> .

<http://my.ontolo.gy/test> rdf:type owl:Ontology ;
                         rdfs:label "Ontologia"@pl ;
                         rdfs:comment "Komentarz"@pl ;
                         owl:imports bibo: ,
                                     <http://schema.rdfs.org/all> ,
                                     <http://www.w3.org/2006/vcard/ns> ,
                                     <http://www.w3.org/ns/locn> .

###  http://my.ontolo.gy/test#title

:title rdf:type owl:DatatypeProperty ,
             owl:FunctionalProperty ;
    rdfs:label "tytuł"@pl ;
    skos:definition """definition""" ;
    rdfs:comment """komentarz"""@pl ;
    rdfs:range xsd:string ;
    rdfs:domain :Annotation ,
                :Entity .

And after saving it back to the file:

@prefix : <http://my.ontolo.gy/test#> .
@prefix dc: <http://purl.org/dc/elements/1.1/> .
@prefix owl: <http://www.w3.org/2002/07/owl#> .
@prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#> .
@prefix xml: <http://www.w3.org/XML/1998/namespace> .
@prefix xsd: <http://www.w3.org/2001/XMLSchema#> .
@prefix bibo: <http://purl.org/ontology/bibo/> .
@prefix foaf: <http://xmlns.com/foaf/0.1/> .
@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#> .
@prefix skos: <http://www.w3.org/2004/02/skos/core#> .
@prefix midas: <http://my.ontolo.gy/test#> .
@prefix vcard: <http://www.w3.org/2006/vcard/ns#> .
@prefix dctype: <http://purl.org/dc/dcmitype/> .
@prefix schema: <http://schema.rdfs.org/all#> .
@prefix dbpedia: <http://dbpedia.org/ontology/> .
@prefix dcterms: <http://purl.org/dc/terms/> .
@prefix location: <http://www.w3.org/ns/locn#> .
@base <http://my.ontolo.gy/test> .

<http://my.ontolo.gy/test> rdf:type owl:Ontology ;

                           rdfs:label "Ontologia"@pl ;

                           rdfs:comment "Komentarz"@pl ;

                           owl:imports bibo: ,
                                       <http://schema.rdfs.org/all> ,
                                       <http://www.w3.org/2006/vcard/ns> ,
                                       <http://www.w3.org/ns/locn> .


#################################################################
#
#    Object Properties
#
#################################################################


###  http://my.ontolo.gy/test#title

:title rdf:type owl:ObjectProperty ;

       rdfs:label "tytuł "@pl ;

       skos:definition "definition" ;

       rdfs:comment "komentarz"@pl ;

       rdfs:range xsd:string .





#################################################################
#
#    Data properties
#
#################################################################


###  http://my.ontolo.gy/test#title

:title rdf:type owl:DatatypeProperty ,
                owl:FunctionalProperty ;

       rdfs:label "tytuł "@pl ;

       skos:definition "definition" ;

       rdfs:comment "komentarz"@pl ;

       rdfs:domain :Annotation ,
                   :Entity .





#################################################################
#
#    Classes
#
#################################################################


###  http://my.ontolo.gy/test#Annotation

:Annotation rdf:type owl:Class .



###  http://my.ontolo.gy/test#Entity

:Entity rdf:type owl:Class .




###  Generated by the OWL API (version 3.4.2) http://owlapi.sourceforge.net

Answer 1

The root cause for this is that, during parsing, (by the OWL API)

rdfs:range xsd:string

is considered to be asserting that the range is the xsd:string /class/. This is clearly a problem. I've seen it before when ontologies contain erroneous declarations of xsd:string as a class, which is a violation of the OWL 2DL profile.

The origin of this appears to be in the schema.rdfs.org/all import, where this kind of construct can be found:

rdfs:range [ a owl:Class; owl:unionOf (xsd:decimal xsd:string) ];

In order for this to parse, the datatype IRIs need to be coopted to be class IRIs. This is the first OWL profile violation, and the other violations are caused by its side effects.

The schema ontology appears to be RDF rather than OWL, so I'm not sure if it makes sense to try and fix these issues.