Using Jena as a SPARQL endpoint

Posted on January 11, 2010 by Gareth

I’ve been involved in a few projects at work over the last couple of years that have made use of Semantic Web technologies (triple stores, RDF, OWL, SPARQL etc). For most of these I’ve made of ARC, a really great PHP library by Ben Nowack for interacting with RDF and triple stores. As great as ARC is, it does have a few drawbacks such as being limited to MySQL triple stores, some issues with OPTIONAL queries and it doesn’t entirely support the SPARQL specification.

For these reasons and for general flexibility, my current project wanted to be able to easily swap the underlying triple store from ARC to Jena as needed so I needed to investigate how to expose a Jena triple store as a SPARQL endpoint. After working this out, I now really really appreciate how easy ARC makes this.

Jena doesn’t appear to ship with the ability to expose the ARQ SPARQL processor as a SPARQL endpoint and hence you need to make use of a separate piece of software called Joseki. The following is the list of things I needed to do to get this working in my environment. Note that your setup may have different requirements and also I may have completely misunderstood the best way of doing this!

Setup a database to use as your triple store and get a JDBC driver so Joseki can interact with it from Java
Download and extract Joseki
Add the JDBC driver to the Joseki classpath (e.g. for Windows by adding the following line to bin\joseki_path.bat: set CP=%CP%;C:\my_jdbc_driver\my_jdbc_driver.jar)

Add the following to joseki-config.ttl:

 
   rdf:type            joseki:Service ;
   rdfs:label          "My Project SPARQL/Update" ;
   joseki:serviceRef   "sparql/myproject/update" ;
   joseki:dataset       ;
   joseki:processor    joseki:ProcessorSPARQLUpdate .

 
   rdf:type            joseki:Service ;
   rdfs:label          "SPARQL" ;
   joseki:serviceRef   "sparql/myproject/read" ;
   joseki:dataset       ;
   joseki:processor    joseki:ProcessorSPARQL_FixedDS .

 
   rdf:type            ja:RDFDataset ;
   rdfs:label          "My Project" ;
   ja:defaultGraph      .

 
   rdf:type            ja:RDBModel ;
   ja:connection       [
                         ja:dbType "MySQL" ;
                         ja:dbURL           ;
                         ja:dbUser         "myproject-database-username" ;
                         ja:dbPassword     "myproject-database-password" ;
                         ja:dbClass        "com.mysql.jdbc.Driver"
                        ] ;
   ja:reificationMode    ja:minimal ;
   ja:modelName        "DEFAULT" .

Set the JOSEKIROOT environment variable to the location you extracted Joskei
Run Joseki (from it’s directory) by executing bin/rdfserver.bat

Note that I wanted to be able to make use of SPARUL to update data using the SPARQL endpoint. In ARC I can use SPARQL+ (which is effectively the same for my purposes) on the same endpoint as normal SPARQL queries. For Joseki however, I needed to expose two different endpoints, one for standard SPARQL queries and one for updating.

The one thing I haven’t yet worked out how to do it to be able to use named graphs in my Jena triple store when inserting data. I discovered that the SPARUL update specification requires you to create the graph first (unlike ARC’s SPARQL+) but executing e.g. CREATE GRAPH <http://mygraph/> seems to fail silently as any following INSERT INTO <http://mygraph/> statement fails saying that the graph doesn’t exist. Something to keep investigating. It may be something to do with support for the different types of Jena store (RDB, SDB, TDB, etc) which I don’t fully understand yet (I think my instructions above are using RDB which appears to be old but I couldn’t get TDB or SDB working at all).

So all in all I’m pleased to have worked out how to set this up but I will most certainly continue to use ARC where possible as Jena environments seem unnecessarily complex (although this might simply be because it tends to support the W3 specifications fully!).

36 thoughts on “Using Jena as a SPARQL endpoint”

Martin Giese on March 26, 2010 at 14:15 said:

Hmm. Is there no way to just create a Jena Model, maybe an inference model, in Java, and then create an endpoint that fetches data from that Model?

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garethj on March 27, 2010 at 04:23 said:

Hey Martin. I imagine you could do something like that but I already had a MySQL database and was using Joseki to avoid having to write any Java. That's probably the right way to try though.

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- Erdem Begenilmis on March 9, 2011 at 12:56 said:
  
  Hi.
  
  I am new in Joseki. I try to get data from my local database by joseki sparql endpoint (http://localhost:2020/sparql). However, query does not return any data even if for simple queries like “Select ?s ?p ?o Where { ?s ?p ?o. }”. How can I fix it ?
  
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  - garethj on March 10, 2011 at 08:21 said:
    
    Have you tried setting Joseki up using the quickstart instructions (http://www.joseki.org/start.html) and does that result in something running on port 2020? For your local database setup, maybe try some of the instructions here: http://www.joseki.org/configuration.html
  - Erdem Begenilmis on March 10, 2011 at 08:45 said:
    
    Hi.
    Thanks a lot. I solved that problem.
    
    But now I face with a new issue. I need to merge to sparql results which is one set from “dbpedia” and another set from my localhost. So, I tried to run queries for my local store from an external server like “http://www.sparql.org/query.html”. It didn’t work. How can make my local store accesible from remote external services through joseki ?
  - garethj on March 10, 2011 at 16:18 said:
    
    If I understand your problem correctly, you need to expose your Joseki installation on the public Internet. sparql.org will interpret ‘localhost’ as itself, not your local server.
- sushen jamwal on January 29, 2012 at 11:40 said:
  
  Hii..Im new to joseki..i have followed the instruction set given stating set the josekiroot and the classpath including all the libraries in joseki-3.4.4\bin..next when i tried to execute rdfserver.bat i get an error stating: The system cannot find the specified path. Error: could not find or load main class files\joseki-3.4.4\etc\log4j.properties. please help me.
  
  Reply ↓
Thomas on April 15, 2010 at 13:24 said:

I just learned that #mem (and obviously #jdbc) datasets are not supported. In Joseki-3.4.1 the creation of named graphs are supported with TDB 0.8.3 (0.8.5 will not work) datasets. See http://openjena.org/wiki/TDB for more information for downloads and joseki integration.

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garethj on April 16, 2010 at 03:04 said:

Thanks Thomas – useful info.

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Ziya Akar on July 21, 2010 at 13:36 said:

Hi, Do you have any example about sending Sparql Update request to a Joseki server programmatically in Java?Thank you.

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garethj on July 21, 2010 at 14:56 said:

Sorry, all my interaction with the servers was using ARC which is PHP-based. I assume this can be achieved with Jena using Joseki as a SPARQL endpoint so probably worth checking out the Jena documentation.

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Martin on November 8, 2010 at 20:17 said:

I´m trying to send queries using PHP to a Sparql endpoint using Koseki. But I still not understand how should i interact with the remote Server. Should i send the queries to the follwing adresse: http://localhost/joseki/sparql? i tried it but it doesn´t work! Do you have any idea?
Martin

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- garethj on November 9, 2010 at 08:49 said:
  
  Hi Martin. I think by default Joseki starts a server on port 2020 at the following endpoint: http://localhost:2020/sparql
  Does that work for you?
  
  Reply ↓
gucci shirts on February 24, 2011 at 06:24 said:

Something to keep investigating. It may be something to do with support for the different types of Jena store

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Andrea Tabarelli de Fatis on March 23, 2011 at 21:11 said:

hi! I’m trying to use Joseki with tdb. Anyone knows if it is possible to invoke SPARQL queries to tdb triple store directly with php pages??
Or I must use the joseki gui or command line?

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- Andrea Tabarelli de Fatis on March 23, 2011 at 23:34 said:
  
  or also directly also from sdb dataset..
  
  Reply ↓
- garethj on March 24, 2011 at 10:25 said:
  
  Joseki implements the SPARQL protocol (http://www.w3.org/TR/rdf-sparql-protocol/ ) so you should just be able to execute HTTP requests from PHP (using fopen or curl) to your SPARQL endpoint. See http://www.joseki.org/protocol.html for details. I would assume the Joseki GUI and command line just interact with this endpoint but I’ve not actually checked.
  
  Reply ↓
  - Andrea Tabarelli de Fatis on March 24, 2011 at 23:01 said:
    
    Thank you very much I’ll try it as soon as possible.
  - Andrea Tabarelli de Fatis on March 27, 2011 at 15:45 said:
    
    Ok now I’m able to invoke and save the triple results of a Query Sparql. But you know if it’s possible to save also the format of results that Joseki realize? With the html interface of Joseki the output is in xml with xsl trasformation. For example with the request ( http://localhost:2020/sparql?query=SELECT+*+{+%3Fs+%3Fd+%3Ff+}%0D%0A&default-graph-uri=&output=xml&stylesheet=sparqlxml2exhibitjson.xsl ) with joseki interface in the browser I have the data in xml with xsl transformation in Json formats. Is possible to get this format also with curl?
    
    thank you
  - garethj on March 28, 2011 at 13:40 said:
    
    You can use the HTTP Accept header to specify the required output format, or use the ‘accept’ URL parameter. See http://www.joseki.org/protocol.html for details.
  - Andrea Tabarelli de Fatis on March 28, 2011 at 21:46 said:
    
    great! It works properly. Now I’ll try to manage the Sdb triple store with php..
Andrea Tabarelli de Fatis on March 30, 2011 at 22:18 said:

Anyone knows if I can integrate a reasoner such as Pellet to infere new triple?? and how?
I’m using Joseki with sdb triple store.
I suppose that I have to set properly the config file of Joseki but how?

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- garethj on March 31, 2011 at 08:02 said:
  
  Sorry, that one I don’t know the answer too. I believe it can be done but I’ve no idea how much can be easily automated.
  
  Reply ↓
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Rodrigo on September 19, 2011 at 22:35 said:

Hi,
Can you use Joseki + Terp Syntax ? I only can to perform querys with SPARQL .

Thanks

—
Rodrigo

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- Gareth on September 20, 2011 at 08:53 said:
  
  Sorry Rodrigo, I’ve not heard of Terp and don’t know whether you can use it with Joseki. I would assume not.
  
  Reply ↓
  - sushen jamwal on January 29, 2012 at 11:39 said:
    
    Gareth i am new to joseki , i have tried everything to create a joseki endpoint but i am not able to do it.
    
    Can you help ??
smriti on January 27, 2012 at 16:53 said:

Hii..Im new to joseki..i have followed the instruction set given stating set the josekiroot and the classpath including all the libraries in joseki-3.4.4\bin..next when i tried to execute rdfserver.bat i get an error stating: The system cannot find the specified path. Error: could not find or load main class files\joseki-3.4.4\etc\log4j.properties. please help me.

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- Gareth on January 30, 2012 at 09:15 said:
  
  Hi, sorry but it’s been a long time since I’ve done any work with Joseki and even then it was fairly minimal. It sounds like your classpath isn’t set correctly so I’d check that first. Otherwise, maybe the Joseki mailing list or other support sources could help? http://www.joseki.org/support.html
  
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  - smriti on February 1, 2012 at 09:41 said:
    
    I have checked the classpath and it is correct but still iam not able to run joseki..i have followed the instructions but it is of no help..
  - smriti on February 1, 2012 at 12:48 said:
    
    and thank you for your advice..
  - Gareth on February 3, 2012 at 09:11 said:
    
    I would suggest posting to the Joseki mailing list linked from that support page. There should be Joseki experts listening to that who might be able to help you.

Gareth Jones

Using Jena as a SPARQL endpoint

36 thoughts on “Using Jena as a SPARQL endpoint”

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36 thoughts on “Using Jena as a SPARQL endpoint”

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