DBpedia Live comprises SPARQL and Linked Data access, which are updated via the DBpedia Live Sync API: A lightweight, scalable, faster and multilingual microservice architecture for continuous extraction, retrieval and loading of live DBpedia data.
DBpedia Live is a parallel service to the DBpedia Snapshot Releases that are scheduled every third month and update the main DBpedia SPARQL Endpoint and Linked Data Interface. DBpedia Live allows to retrieve and query “live” (w.r.t. Wikipedia) data about DBpedia resources.
DBpedia Live monitors edits on Wikipedia, and extracts the information of an article after it was changed. The DBpedia Live Sync API transfers the updates to a dedicated online SPARQL database – DBpedia Live SPARQL endpoint – for querying. This continuous extraction allows to query for real-time information and bridges the information gap between quarterly release intervals of the primary (static) SPARQL endpoint.
- DBpedia Live SPARQL Endpoint: The DBpedia-Live SPARQL Endpoint can be accessed at http://live.dbpedia.org/sparql.
- DBpedia-Live Statistics: Some simple extraction statistics are provided at http://live.dbpedia.org/live/.
- Updates: The N-Triples files containing the updates can be found at http://downloads.dbpedia.org/live/changesets.
- DBpedia-Live Sourcecode: https://github.com/dbpedia/extraction-framework/tree/master/live.
- Synchronization Tool: https://github.com/dbpedia/dbpedia-live-mirror/.
- Further Reading:
DBpedia Live System Architecture
The main components of the DBpedia Live system are described on a high level below. If you are interested in more details have a look at the devilopment bible.
- EventStreamsFeeder: The feeder is used in order to fetch information about recent changes of Wikipedia pages. It consumes the Wikimedia EventStreams recentchange stream.
- MappingWiki: DBpedia mappings can be found at http://mappings.dbpedia.org, which is itself a wiki. We also use OAI-PMH to get a stream of updates in DBpedia mappings. Basically, a change of mapping affects several Wikipedia pages, which should all be reprocessed.
- DBpedia Live Extraction Manager: This component is the actual DBpedia-Live extraction framework. When there is a page that should be processed, the framework applies the extractors to it. After processing a page, the newly extracted RDF statements are inserted into the backend data store (the Quad Store functionality of the Virtuoso Universal Server), where they replace the old RDF statements. The newly extracted RDF is also written to a compressed N-Triples file. Mirrors of DBpedia-Live, as well as other applications that should always be in synchronization with our DBpedia-Live endpoint, can download those changeset files and feed them into their own RDF data stores. The extraction manager is discussed in more detail below.
The live-extraction framework is deployed on a server hosted by OpenLink Software. It has a SPARQL endpoint, also operated by OpenLink Software, at http://live.dbpedia.org/sparql, and its status can be viewed at http://live.dbpedia.org/live/.
It has the following features:
- Abstract extraction: The abstract of of a Wikipedia article contains the first few paragraphs of that article. The new framework has the ability to cleanly extract the abstract of an article.
- Mapping-affected pages: Upon a change in mapping, the pages affected by that mapping should be reprocessed and their RDF descriptions should be updated to reflect that change.
- Updating unmodified pages: Sometimes a change in the system occurs, e.g. a change in the implementation of an extractor. This change can affect many pages even if they are not modified. In DBpedia-Live, we use a low-priority queue for such changes, such that the updates will eventually appear in DBpedia-Live, but recent Wikipedia updates are processed first.
- Publication of changesets: Upon modification, old RDF statements are replaced with updated statements. The added and/or deleted statements are also written to N-Triples files and then compressed. Any client application or DBpedia-Live mirror can download the files and integrate (and, hence, update) a local copy of DBpedia. This enables that application to stay in synchronization with our version of DBpedia-Live.
- Development of synchronization tool: The synchronization tool enables a DBpedia-Live mirror to stay in synchronization with our live endpoint. It downloads the changeset files sequentially, decompresses them, and integrates them with another DBpedia-Live mirror.
In addition to the infobox extraction process, the framework has currently 19 extractors which process the following types of Wikipedia content:
- Interlanguage links
- External links
- Page links
- Person data
- SKOS categories
- Page ID
- Revision ID
- Category label
- Article categories
Does DBpedia-Live automatically resume from the point where it has stopped, or start from the current timestamp?
DBpedia-Live will resume at the last point at which it stopped.
The live-updates of DBpedia (changesets) have the structure year/month/day/hour/xxxx.nt.gz. What does it mean if there are some gaps in between, e.g., a folder for some hour is missing?
This means that the service was down at that time.
Are the DBpedia-Live services available via IPv6?
http://dbpedia.org/sparql and http://live.dbpedia.org/sparql are both made available via both IPv6 and IPv4.
Can the speed of processing of DBpedia-Live cope with the speed of data-stream?
According to our statistics, roughly 1.4 Wikipedia articles are modified per second, which works out to about 84 articles per minute. With current resources, DBpedia-Live can process about 105 pages per minute, on average.
Does an article change in Wikipedia result in only 2 files per article (one for delete and one for added triples) or do you spread this over several files?
An article update results in two sets of RDF statements: one for the added statements, and one for the deleted statements. To lower the number of files in our updates folder, we combine the statements about several articles into one file.
Does DBpedia-Live also address the issue of a change in infobox mappings?
If I want to maintain a DBpedia-Live mirror, why do I need to download the latest DBpedia-Live dump from http://live.dbpedia.org/dumps/?
The DBpedia-Live dumps are not currently available. They may be restored in future. You may start from any DBpedia-Live dump, but the more recent the dump, the fewer changeset files will need to be downloaded and applied to the triple store at initial launch. Thus, the fastest strategy is to start from the latest dump.
Where can I find the synchronization tool for DBpedia-Live, i.e., the tool that synchronizes a DBpedia-Live mirror with ours?
You can download the DBpedia Integrator tool from https://github.com/dbpedia/dbpedia-live-mirror.
If I find a bug in the extraction framework, how can I report that bug?
You can use the DBpedia bug tracker on github to post the bug.