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About DBpedia
DBpedia is a community effort to extract structured information from Wikipedia and to make this information available on the Web. DBpedia allows you to ask sophisticated queries against Wikipedia, and to link other data sets on the Web to Wikipedia data. The DBpedia knowledge base, which has been created by extracting stuctured information from Wikipedia, currently describes more than 2.9 million things, including at least 282,000 persons, 339,000 places (including 241,000 populated places), 88,000 music albums, 44,000 films, 15,000 video games, 119,000 organizations (including 20,000 companies and 29,000 educational institutions), 130,000 species and 4400 diseases.
About mappings.dbpedia.org
This wiki contains the infobox-to-ontology and the table-to-ontology mappings which are used by the DBpedia extraction framework as well as the ontology definition itself. The framework collects the templates defined in this Wiki and extracts the Wikipedia content according to them (As of March 2010, only the dump extraction uses the mappings. DBpedia Live is going to follow shortly).
DBpedia Mappings
The type of Wikipedia content that is most valuable for the DBpedia extraction are infoboxes and tables. Infoboxes display an article's most relevant facts as a table of attribute-value pairs on the top right-hand side of the Wikipedia page.
As Wikipedia's infobox template system has decentrally evolved over time, different communities of Wikipedia editors use different templates to describe the same type of things (e.g. infobox_city_japan, infobox_swiss_town and infobox_town_de). Different templates use different names for the same attribute (e.g. birthplace and placeofbirth). As many Wikipedia editors do not strictly follow the recommendations given on the page that describes a template, attribute values are expressed using a wide range of different formats and units of measurement.
In order to overcome the problems of synonymous attribute names and multiple templates being used for the same type of things, the DBpedia project maps Wikipedia templates as well as tables within an article to the DBpedia ontology. These mappings are specified using the DBpedia Mapping Language. The mapping language makes use of MediaWiki templates that define DBpedia ontology classes and properties as well as template/table to ontology mappings.
The following mappings map Wikipedia infoboxes and tables to this ontology:
DBpedia Ontology
The DBpedia ontology is based on OWL and forms the structural backbone of DBpedia. It describes classes, e.g. person, city, country, and properties, e.g. birth place, longitude. Information in Wikipedia articles is then mapped via the above described mapping to this ontology. Most prominently, many Wikipedia pages use so called infoboxes. For instance, the English wikipedia article about London contains a "settlement infobox". This infobox may be mapped to e.g. the class "populated place" (see PopulatedPlace) in the DBpedia ontology and the attributes in the infobox are mapped to properties in the DBpedia ontology. This way, a unified view over all data in infoboxes can be obtained. Since this information conforms to Semantic Web standards, it can be queried and combined by a broad range of tools in a useful way. This increases the value of information entered by the Wikipedia community.
A listing of all classes, properties and datatypes (units of measurement) used by the DBpedia ontology is found below:
- Ontology Classes - OWL classes and their definitons
- Ontology Properties - OWL Object and Datatype properties
- Datatypes
How is the Mapping and the Ontology maintained?
So far, few people inside the DBpedia project maintained the mapping and ontology, but in the spirit of open source projects, control will be handed over to the Wikipedia and DBpedia community. The members of the DBpedia team are not able to extend the mappings to cover all Wikipedia infoboxes and tables, due to the size of the task and the knowledge required to map templates from exotic domains. Therefore, the idea of this Wiki is to enable the interested public to contribute to the definition of DBpedia mappings by updating existing mappings and by adding new mappings to this wiki.
This wiki is read-only. If you like to edit the mappings or ontology schema, please register and the DBpedia team will add you to the editors list.
Tutorials
The Specification of the DBpedia Mapping Language can be found here. Please find below step-by-step tutorials on:
Tools
This wiki provides several tools that help you to edit the mappings and the ontology:
- Ontology View. The ontology view gives you an overview about the current shape of the DBpedia ontology.
- Mapping Validator. When you are editing a mapping, there is a validate button on the bottom of the page. Pressing the button validates your changes for syntactic correctness and highlights inconsistencies such as missing property definitions.
- Extraction Tester. The extraction tester tests a mapping against a set of example Wikipedia pages. This gives you direct feedback about whether a mapping works and how the resulting data will look like.
Mappings for new languages
To create mappings for a new language the following things need to be done:
- Create an account on this mappings wiki (http://mappings.dbpedia.org/index.php?title=Special:UserLogin&type=signup&returnto=Main_Page).
- Contact the DBpedia maintainers (dbpedia-developers@lists.sourceforge.net) to get editor rights on the mappings wiki, and for them to create a new language namespace in the framework and on the wiki.
Create new mappings
To get an idea of how mappings are written, you can look at some example from the English mappings.
To create a new mapping, type the following line into your web browser
http://mappings.dbpedia.org/index.php/Mapping_LANGUAGE:INFOBOXNAME
- replace LANGUAGE by the language code you are currecntly working on (for example mt for Malti)
- replace INFOBOXNAME by the box that you want to create a mapping for (replace spaces with underscores)
e.g.
http://mappings.dbpedia.org/index.php/Mapping_mt:Infobox_album
for the Album infobox on the Malti Wikipedia.
If there is no mapping for this box yet, you will see a page saying "There is currently no text in this page. You can search for this page title in other pages, search the related logs, or edit this page." On the top you can click on "create" and start writing the mapping.
Use new mappings in the extraction
Once that there are mappings for a language, you can run the DBpedia extraction. Several things have to be installed and configured, which is documented at http://wiki.dbpedia.org/Documentation
- Section 1 describes what has to be installed to run the DBpedia extraction framework.
- In 4.1., all things that must be specified before starting the extraction from a dump file are listed. In the file "dump/config.properties" (using the file "dump/config.properties.default" as a template), you can specify the languages for which you want to extract, and which extractors should be used. For example, to run the HomepageExtractor and the MappingExtractor for Malti, specify
languages=mt
extractors.mt=org.dbpedia.extraction.mappings.HomepageExtractor \
org.dbpedia.extraction.mappings.MappingExtractor
- When you run the extraction (see 4.2.), the MappingExtractor will extract the information from the infoboxes that you created a mapping for. The extracted triples will be saved in a file named "mappingbased_properties_hr.nt" in the output directory you specified.
