Hi I'm composing an ontology and my purpose is to extend foaf:Person by adding new properties to it What is the best way to do so: Is it by:

Defining a new subclass of foaf:Person called my:Person and make it a domain of the new properties

Or by directly making foaf:Person the domain of my new properties?

Thanks

asked 08 Jan '12, 02:15

Mutaz's gravatar image

Mutaz
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edited 08 Jan '12, 16:50

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tobyink ♦
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There is no need to create a new class. That's kind of the whole reason the Semantic Web uses URIs as identifiers - it allows terms defined in one ontology to be directly reused in another.

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answered 08 Jan '12, 04:12

tobyink's gravatar image

tobyink ♦
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So you mean I only need to define my new properties on the domain foaf:Person? In this case why sioc:UserAccount is subclassing foaf:OnlineAccount? They could do the same and make foaf:OnlineAccount the domain of the new properties instead of defining sioc:UserAccount and make it the domain. Could you please explain what the difference is?

(08 Jan '12, 04:42) Mutaz Mutaz's gravatar image

sioc:UserAccount has a narrower meaning than foaf:OnlineAccount. sioc:UserAccount is defined as "a user account in an online community site" whereas foaf:OnlineAccount also covers accounts at banking sites, e-commerce sites, etc, which are arguably not online communities. Personally though, I would never cite SIOC as an example of good practice in schema design.

(08 Jan '12, 05:29) tobyink ♦ tobyink's gravatar image

Please check the answer

(08 Jan '12, 06:05) Mutaz Mutaz's gravatar image

So I understand if I want to add domainName to sioc:Site I should do the following:

<owl:DatatypeProperty rdf:about="http://example.com/ont#domainName">
<rdfs:domain rdf:resource="http://rdfs.org/sioc/ns#Site"/>
<rdfs:range rdf:resource="http://www.w3.org/2001/XMLSchema#string"/>
</owl:DatatypeProperty>

Without the need for subclassing sioc:Site, right? Does this affect inferencing and applying semantic web technologies in the future versus defining my own subclasses and having them in the property domain?

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answered 08 Jan '12, 05:59

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Mutaz
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edited 08 Jan '12, 06:00

Yes, that should be fine. For OWL inferencing, you may also want to add a triple along the lines of { http://example.com/ont# owl:imports http://rdfs.org/sioc/ns# . }

(08 Jan '12, 06:25) tobyink ♦ tobyink's gravatar image

Thanks a bunch

(08 Jan '12, 06:35) Mutaz Mutaz's gravatar image

While you don't have to create a new class, you still CAN do so by giving some semantic constraints. So, going with your example of my:Person being a subclass of foaf:Person, let's say that you want each instance of my:Person to have a property my:hasFather with both (local) domain and range being my:Person. By "local", I mean that the range (and likewise the domain) is not a global feature of the property my:hasFather (something that you would express by an rdfs:range axiom), but it will only be inferrable for instances of class my:Person - the property my:hasFather may alternatively be used for things outside the class my:Person (such as animals), in which case the range of the property will be undetermined, unless specified elsewhere. You can get this behavior by the following subclass axioms:

(1)

# every my:Person is a foaf:Person
my:Person rdfs:subClassOf foaf:Person .

# every my:Person has exactly one father
# (not what you were asking for, but it makes some sense)
my:Person rdfs:subClassOf [
    owl:onProperty my:hasFather ;
    owl:cardinality "1"^^xsd:nonNegativeInteger ] .

# local range of my:hasFather: 
# the father of a my:Person is himself a my:Person
my:Person rdfs:subClassOf [
    owl:onProperty my:hasFather ;
    owl:allValuesFrom my:Person ] .

# local domain (what you were asking for!): 
# expressed by inverse property!
my:Person rdfs:subClassOf [
    owl:onProperty [ owl:inverseOf my:hasFather ] ;
    owl:allValuesFrom my:Person ] .

So, say you have within your data the triple

(2) my:alfred my:hasFather my:bob .

you will not immediately learn that my:alfred or my:bob are instances of my:Person. However, if you have the additional triple

(3a) my:alfred rdf:type my:Person .

then you will learn that my:bob is also a my:Person, as this is the local range of my:hasFather with regard to class my:Person. And, likewise, if you have the additional triple

(3b) my:bob rdf:type my:Person .

then you will learn that my:alfred is also a my:Person, as this is the local domain of my:hasFather with regard to class my:Person.

Things you should avoid:

  • Although quite obvious, it should be stated anyways: Do not make class foaf:Person a subclass of any of the given restriction class expressions (neither the owl:cardinality nor the owl:allValuesFrom expressions), as this would change the intended meaning of class foaf:Person: Suddenly, every foaf:Person will have some my:hasFather relationship!

  • Less obvious: Also do not make those restriction class expressions subclasses of foaf:Person, with the idea to have them "in the middle" between foaf:Person and my:Person, as this would have the semantic side effect that every individual that can be inferred to have either exactly one or zero(!) properties my:hasFather will become a foaf:Person.

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answered 09 Jan '12, 10:08

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Michael Schn... ♦
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Asked: 08 Jan '12, 02:15

Seen: 19,578 times

Last updated: 09 Jan '12, 10:08