View source for RDF in Semantic Mediawiki

{{#set: Section:Code Notes
|Date:2020
}}


'''Notes on importing ontologies to SMW
'''

=How to importing ontology?=
The documentation on importing existing ontologies to SMW in its Manual Section [https://www.semantic-mediawiki.org/wiki/Help:Import_vocabulary Help:Import_vocabulary]

==MediaWiki:Smw_import==
To import existing Semantic Web ontologies SMW uses the <nowiki>MediaWiki:Smw_import_ONTOGOLOGYNAME</nowiki> pages, such as [[MediaWiki:Smw_import_foaf]] for the Friend Of A Friend ontology.

SMW manual mentions the following ontologies, some of which are already present in SMW instances, others need to be create from the examples provided by the SMW manual: 

* [[MediaWiki:Smw_import_foaf|foaf]] Friend Of A Friend [https://www.semantic-mediawiki.org/wiki/MediaWiki:Smw_import_foaf Smw_import_foaf example]
* [[MediaWiki:Smw_import_rdfs|rdfs]] RDF Schema [https://www.semantic-mediawiki.org/wiki/MediaWiki:Smw_import_rdfs Smw_import_rdfs example]
* [[MediaWiki:Smw_import_owl|owl]] Web Ontology Language (OWL) [https://www.semantic-mediawiki.org/wiki/MediaWiki:Smw_import_owl Smw_import_owl example]
* [[MediaWiki:Smw_import_skos|SKOS]] Simple Knowledge Organization System (SKOS) [https://www.semantic-mediawiki.org/wiki/MediaWiki:Smw_import_skos Smw_import_skos example]
* [[MediaWiki:Smw_import_dc|dc]] Dublin Core Metadata [https://www.semantic-mediawiki.org/wiki/MediaWiki:Smw_import_dc Smw_import_dc example]
* [[MediaWiki:Smw_import_dcterms|dcterms]] DCMI Metadata Terms [https://www.semantic-mediawiki.org/wiki/MediaWiki:Smw_import_dcterms Smw_import_dcterms example]
* [[MediaWiki:Smw_import_bibo|bibo]] Bibliographic Ontology [https://www.semantic-mediawiki.org/wiki/MediaWiki:Smw_import_bibo Smw_import_bibo example]
* [[MediaWiki:Smw_import_frbr|frbr]] Functional Requirements for Bibliographic Records [https://www.semantic-mediawiki.org/wiki/MediaWiki:Smw_import_frbr Smw_import_frbr example]

I will be adding and making use of in this wiki of the [[MediaWiki:Smw_import_foaf|foaf]] ontology.


==Property pages==
Each one of the properties listed in the MediaWiki:Smw_import_XYZ page has to be created with the following template

<pre>
* [[Imported from::ONTOLOGYNAME:PROPERTY]] 
* [[Has property description::DESCRIPTION OF PROPERTY.@langcode]] 

[[Category:Imported vocabulary]]{{DISPLAYTITLE:ONTOLOGYNAME:PROPERTY}}
</pre>


As for instance the [[Property:foaf:name]]:

<pre>
* [[Imported from::foaf:name]] 
* [[Has property description::A name for some thing or agent.@en]] 

[[Category:Imported vocabulary]]{{DISPLAYTITLE:foaf:name}}
</pre> 

Note in that [[Property:foaf:name| Property page]] that the '''Property Type''' is not declared on this page, but its assignment is done at the [[MediaWiki:Smw_import_foaf|ontology import page]]

Because it can be quite tedious to create all those Property pages manually we can resort to scripts which create wiki pages, by interaction with the Mediawiki API <ref>See some Python the scripts for this at https://gitlab.com/Castro0o/wikitools </ref>

After the Properties have been created ensure to run MW's scripts:
* <code>maintenance/runJobs.php</code> to run pending jpbs
* <code>maintenance/update.php</code> since we made change to Property types


The created Properties should be visible in [[Special:Properties]]

==Classes <nowiki>==</nowiki> Categories==
As it is visible in [[MediaWiki:Smw_import_foaf]] the entries '''Person''' and '''Organization'''  both have'''Category as their type''', which makes them not a Property but a Category. And as a result they do not have property pages but category pages: [[:Category:Person]], [[:Category:Organization]].


In the category page, you have to inform SWM that this is an imported class from an external vocabulary. This is done via the ''[[Help:Special property Imported from|Imported from]]'' [[Help:Special properties|special property]] declaration: <pre>[[Imported from::foaf:Person]]</pre>


'''Why Categories?'''

The reason they are Categories is because '''SMW uses categories to state that something is an element of a ''class'', as categories are mapped internally as rdf:type.'''. In Semantic Web ontologies classes create semantic classification groupings. And according to the RDF Schema" "rdf:type is an instance of rdf:Property that is used to state that a resource is an instance of a class." <ref>https://www.w3.org/TR/rdf-schema/#ch_type</ref>


<blockquote>
A class in OWL is a classification of individuals into groups which share common characteristics. If an individual is a member of a class, it tells a machine reader that it falls under the semantic classification given by the OWL class.<ref>http://www.linkeddatatools.com/introducing-rdfs-owl</ref></blockquote>

The FOAF specification<ref>http://xmlns.com/foaf/spec/#sec-crossref</ref> stipulates the following classes: <code>Agent | Document | Group | Image | LabelProperty | OnlineAccount | OnlineChatAccount | OnlineEcommerceAccount | OnlineGamingAccount | Organization | Person | PersonalProfileDocument | Project 
</code> out of which the [[MediaWiki:Smw_import_foaf]] uses Person and Organization.



== Annotating ==

As an example of semantic annotations, which use and imported vocabulary I will use the pages [[Rana Hamadeh - The Ten Murders of Josephine]], [[Rana Hamadeh]] and [[Witte de With Center for Contemporary Art]]

In [[Rana Hamadeh - The Ten Murders of Josephine]] belongs to Class [[:Category:Project]] 
<pre>
* '''Location:''' [[Foaf:maker::Witte de With Center for Contemporary Art]], Rotterdam
* '''Author:''' [[Foaf:maker::Rana Hamadeh]]

[[Category:Project]]
</pre>


[[Rana Hamadeh]] belongs to the Class [[:Category:Person]] with the FOAF descriptors:
<pre>
{{#set: Foaf:name=Rana Hamadeh
|Foaf:homepage=http://ranahamadeh.com/
|Foaf:depiction=https://dutchartinstitute.eu/image/2014/5/12/r_hamadeh_self_portrait_2.jpg
|Foaf:knows=User:Andre|Jorg Schellekens
|Foaf:made=Rana Hamadeh - The Ten Murders of Josephine
}}
[[Category:Person]]
</pre>

[[Witte de With Center for Contemporary Art]] belongs to the Class [[:Category:Organization]]
<pre>{{#set: foaf:website=http://www.wdw.nl/en/
|foaf:knows=Rana Hamadeh
|foaf:made=Rana Hamadeh - The Ten Murders of Josephine
}}</pre>

=== Inverse Properties: not supported by SMW ===
It is worth noting that both [[Rana Hamadeh]] and [[Witte de With Center for Contemporary Art]] use the [[Property:foaf:made]] which is the inverse of [[Property:foaf:maker]].
In a normal situation, since they are inverse we would not need to also define the [[Property:foaf:made]] in [[Rana Hamadeh]] and [[Witte de With Center for Contemporary Art]]. However '''SMW Semantic MediaWiki does not internally support inverse relationships'''. So  a bit of redundancy is necessary 

=== Ask ===
We can ask who '''made''' something

<pre>
{{#ask: [[Foaf:made::+]]
 |?Foaf:made
 |format=broadtable
 |limit=50
 |offset=0
 |link=all
 |sort=
 |order=asc
 |headers=show
 |mainlabel=Foaf:maker
 |searchlabel=... further results
 |class=sortable wikitable smwtable
}}
</pre>

{{#ask: [[Foaf:made::+]]
 |?Foaf:made
 |format=broadtable
 |limit=50
 |offset=0
 |link=all
 |sort=
 |order=asc
 |headers=show
 |mainlabel=Foaf:maker
 |searchlabel=... further results
 |class=sortable wikitable smwtable
}}


Or What entities know other entities and what aretheir classes.  In  other words  Who '''knows''' Who

<pre>
{{#ask: [[Foaf:knows::+]]
 |?Category=Class
 |?Foaf:knows
 |format=broadtable
 |limit=50
 |offset=0
 |link=all
 |sort=
 |order=asc
 |headers=show
 |mainlabel=Entity
 |searchlabel=... further results
 |class=sortable wikitable smwtable
}}
</pre>

{{#ask: [[Foaf:knows::+]]
 |?Category=Class
 |?Foaf:knows
 |format=broadtable
 |limit=50
 |offset=0
 |link=all
 |sort=
 |order=asc
 |headers=show
 |mainlabel=Entity
 |searchlabel=... further results
 |class=sortable wikitable smwtable
}}

== RDF export ==

----

[[Section::Code Notes]]
[[Date::2020]]