Release: Freebase 0.1 (beta)

September 14th, 2009

The Freebase extension is now available for download. It enables you to query Freebase using conventional inline queries in a Semantic MediaWiki (SMW). Querying Freebase is easily achieved by simply adding the parameter source=freebase:

{{#ask: [[Category:City]] [[located in::Germany]]
| ?population
| source=freebase

This queries freebase for cities that are located in Germany and their population. You can see the result of this query here.

More information about how to use it, installation instructions, more examples, and a playground where you can try out your ideas can be found in the demo wiki.

I am looking forward to your opinions. This work is part of my master’s thesis work at AIFB Karlsruhe and your comments can be very helpful for both further development of the extension and my work.

Please note that it is a beta version. It may contain errors.

Welcome to my blog

July 29th, 2009

First let me briefly introduce myself: My name is Basil Ell and I am currently working for my master thesis at AIFB Karlsruhe – supervised by Denny Vrandečić.

In this blog I intend to report about my development efforts concerning Semantic MediaWiki (SMW) that strive in enabling SMW to be used as a data integration framework. [1] I set up a demo wiki where you can find documentation and examples, observe the state of my work in progress, and experience current possibilities and limitations.

As a first step in this direction I am currently realizing a mediator that enables to route queries to Freebase [2].

The initial motivation was to make data integration as simple as possible. Since the syntax of SMW’s query language is closely related to wiki text [3] for the reason of usability I do not introduce any new syntax in order to enable users that are already familiar with the query syntax to make use of data integration.

Briefly sketched technically an askQL query is transformed to MQL (Metaweb Query Language – the query language of Freebase) and passed to Freebase which results in a JSON formatted response. Relevant information is extracted and the same type of result object is created as when performing a local query. The transformation requires some mapping information which can be stored as properties in wiki pages. I will provide detailed information in later posts.

With this first step

  1. I hope to make a useful contribution to the SMW-utilizing community and
  2. to identify requirements to be able to specify a mediator’s interface that opens the way for the integration of further external data sources.

I see mediating as a first step to data aggregation. Making external data independent from its internal representation allows merging data from various sources. This allows formulating querys that incorporate a set of (probably external) sources.

  1. Actually several data integration extensions for SMW do already exist. External Data, Wibit, Sparqling, and the SMW+ Data Import Extension are known to me. The difference to my approach is, that I want to enable aggregation of local and integrated data. Therefore I want to enable using the standard inline query syntax for querying external sources. []
  2. Freebase is a vast, free, open online database of structured knowledge, powered and maintained by Metaweb Technologies ( (The MQL Reference Guide) []
  3. Krötzsch, M., Vrandečić, D., Völkel, M., Haller, H., and Studer, R. 2007. Semantic Wikipedia. Web Semant. 5, 4 (Dec. 2007), 251-261. DOI=