Help:RDF export

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Based on the user's semantic annotations of articles, Semantic MediaWiki generates machine-readable documents in OWL/RDF format, that can be accessed via Special:ExportRDF. This article explains how annotations are formally interpreted in the OWL ontology language, and how a sutiable RDF serialisation is generated.

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Using the export functionality

Users can easily access the generated RDF via the page Special:ExportRDF by entering a list of articles into the input field. The export will contain one OWL/RDF specification with various description blocks for exported elements. In addtion to the requested articles, the export will also contain basic declarations for any further elements (such as mentioned instances, properties, and classes). There are two settings that further influence the set of exported articles:

  • Recursive export. Every article usually has relations to various other articles. Normally, those other articles are just declared briefly such that tools can find further RDF specifications for htem if desired. By enabling recursive export, all information about the encountered objects will be exported right away. Since this process is continued for all ruther objects, this option can lead to large results.
  • Backlinks. The RDF data model is based on directed graphs. When exporting an article, one usually exports only the statements within which the corresponding element occurs as a subject, and the exported document does not include incoming links. This restricts RDF browsers, since they cannot access all elements that have some relationship to something without retrieving the whole RDF first. For this reason, one can enable the export of backlinks. All articles that have relations to any of the exported articles then will also be exported.

The server administrator can restrict the availability of the above options, and can set default values cases where no parameters can be given (see below). The reason is that the above options, especially in combination, can easily lead to the export of major parts of the wiki in RDF, which might overly impair the performance of large sites.

In addtion to the form at Special:ExportRDF, one can also retrieve RDF by calling appropriate URLs directly. This is suitable for linking to RDF specifications directly. In its basic form, this is achieved by appnding a (URL ecnoded version of an) article name to the URL of the export service. For instance, one can link to

http://wiki.ontoworld.org/index.php/Special:ExportRDF/ESWC2006

to get this RDF directly. Alternatively, the article name can also be specified as a GET parameter "page" within the URL, e.g.

http://wiki.ontoworld.org/index.php?title=Special:ExportRDF&page=ESWC2006

Further GET parameters are available to set the above options. Backlinks can be enabled or disabled by setting "backlinks" to 1 or 0, respectively. Recursive export is enabled or disabled by setting "recursive" to 1 or 0. Both settings will be ignored if disabled by the administrator. If no settings are given, site-wide default values apply. For example, wiki.ontoworld.org always exports RDF with backlinks.

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The exported data in detail

Mapping wiki-pages to ontology elements

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Restrictions for OWL DL

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