IMPORTANT NOTE:

There is a newer and DBpedia Databus compatible version of the DBpedia Lookup here: https://github.com/dbpedia/dbpedia-lookup. The discussion concerning the transition to the new service can be found here: https://forum.dbpedia.org/t/new-dbpedia-lookup-application/607

DBpedia Lookup

DBpedia Lookup is a web service that can be used to look up DBpedia URIs by related keywords. Related means that either the label of a resource matches, or an anchor text that was frequently used in Wikipedia to refer to a specific resource matches (for example the resource http://dbpedia.org/resource/United_States can be looked up by the string "USA"). The results are ranked by the number of inlinks pointing from other Wikipedia pages at a result page.

Web APIs

Two APIs are offered: Keyword Search and Prefix Search. A hosted version of the Lookup service is available on the DBpedia server infrastructure.

Keyword Search

The Keyword Search API can be used to find related DBpedia resources for a given string. The string may consist of a single or multiple words.

Example: Places that have the related keyword "berlin"

http://lookup.dbpedia.org/api/search/KeywordSearch?QueryClass=place&QueryString=berlin

Prefix Search (i.e. Autocomplete)

The Prefix Search API can be used to implement autocomplete input boxes. For a given partial keyword like berl the API returns URIs of related DBpedia resources like http://dbpedia.org/resource/Berlin.

Example: Top five resources for which a keyword starts with "berl"

http://lookup.dbpedia.org/api/search/PrefixSearch?QueryClass=&MaxHits=5&QueryString=berl

Parameters

The query parameters accepted by the endpoints are

• QueryString: a string for which a DBpedia URI should be found.
• QueryClass: a DBpedia class from the Ontology that the results should have (for owl#Thing and untyped resource, leave this parameter empty).
• MaxHits: the maximum number of returned results (default: 5)

JSON support

By default all data is returned as XML, the service also retuns JSON to any request including the Accept: application/json header.

Running a local mirror of the webservice

Clone and build DBpedia Lookup

git clone git://github.com/dbpedia/lookup.git
cd lookup
mvn clean install

Download and configure the index

You can get our indexes from HERE

Run the server

`./run Server [PATH TO THE INDEX]/[VERSION]/`

E.g:

`./run Server /opt/dbpedia-lookup/2015-04`

Note: The index file must be decompressed

Available versions:

• current - from Latest DBpedia Dump (2015-10)

Available languages (i18n working in progress):

• en - English

The server should now be running at http://localhost:1111

Rebuilding the index

Rebuilding an index is usually not required, if you only intend on running a local mirror of the service you can donwload a prebuilt index as outlined above.

To re-build the index you will require

• DBpedia datasets
• Wikistatsextractor output - wikistatsextractor is a drop-in replacement of pignlproc
• Unix

Get the following DBpedia datasets

from http://downloads.dbpedia.org/2015-10/core-i18n/en/

• redirects_en.nt (or .ttl)
• short_abstracts_en.nt (or .ttl)
• instance_types_en.nt (or .ttl)
• article_categories_en.nt (or .ttl)

from http://downloads.dbpedia.org/2015-10/core

• instance_types_en.ttl
• instance_types_sdtyped_dbo_en.ttl
• instance_types_transitive_en.ttl

Concatenate all data and sort by URI

This is necessary because indexing in sorted order is significantly faster.

  cat instance_types_en.nt (or .ttl)  \
      short_abstracts_en.nt (or .ttl) \
      article_categories_en.nt (or .ttl) \
      instance_types_en.ttl  \
      instance_types_sdtyped_dbo_en.ttl \
      instance_types_transitive_en.ttl | sort >all_dbpedia_data.nt (or .ttl)

Get the dataset redirects_en.nt (or .ttl)

Redirects are not indexed, but they are excluded as targets of lookup.

Run Indexer

The indexer has to be run twice:

1. with the DBpedia data

    ./run Indexer lookup_index_dir redirects_en.nt (or .ttl) all_dbpedia_data.nt (or .ttl)
   

2. with the wikistatsextractor data

    ./run Indexer lookup_index_dir redirects_en.nt (or .ttl) pairCounts
   

Support and feedback

The best way to get support or give feedback on the Lookup project is via the DBpedia discussion mailing list. More technical queries about the code base should be directed to the DBpedia developers mailing list.

The DBpedia wiki also has useful information on the project.

Maintainers

• Kunal Jha @Kunal-Jha
• Sandro Coelho @sandroacoelho
• Pablo Mendes @pablomendes (less active)
• Max Jakob @maxjakob (less active)
• Matt Haynes @matth (less active)