squin-users — A discussion list for users of SQUIN.

[Squin-users] Squin build error

[Wael H. <wae...@mi...>]

Hello,

My name is wael and I'm trying to start using SQUIN but I've had some
problems. I think (from what I read) that it has happened because of the newest versions of
Jena and ARQ, especially with the latter.
I tried using the API through the example from the site: https://github.com/castagna/squin/blob/master/squin-example/src/main/java/org/squin/example/HelloWorld.java

And I got the following error message:

Exception in thread "main" java.lang.NoSuchMethodError: com.hp.hpl.jena.sparql.algebra.OpVars.allVars(Lcom/hp/hpl/jena/sparql/algebra/Op;)Ljava/util/Collection;
       at org.squin.dataset.query.arq.QueryEngine.initializeVarDictionary(QueryEngine.java:151)
       at org.squin.engine.LinkTraversalBasedQueryEngine.createExecutionContext(LinkTraversalBasedQueryEngine.java:137)
       at org.squin.engine.LinkTraversalBasedQueryEngine.eval(LinkTraversalBasedQueryEngine.java:126)
       at com.hp.hpl.jena.sparql.engine.QueryEngineBase.evaluate(QueryEngineBase.java:138)
       at com.hp.hpl.jena.sparql.engine.QueryEngineBase.createPlan(QueryEngineBase.java:109)
       at com.hp.hpl.jena.sparql.engine.QueryEngineBase.getPlan(QueryEngineBase.java:97)
       at org.squin.engine.LinkTraversalBasedQueryEngineFactory.create(LinkTraversalBasedQueryEngineFactory.java:54)
       at com.hp.hpl.jena.sparql.engine.QueryExecutionBase.getPlan(QueryExecutionBase.java:266)
       at com.hp.hpl.jena.sparql.engine.QueryExecutionBase.startQueryIterator(QueryExecutionBase.java:243)
       at com.hp.hpl.jena.sparql.engine.QueryExecutionBase.execResultSet(QueryExecutionBase.java:248)
       at com.hp.hpl.jena.sparql.engine.QueryExecutionBase.execSelect(QueryExecutionBase.java:94)
       at HelloWorld.main(HelloWorld.java:43)


I would like to ask for your help to solve this problem.

Thank you and Best Regards

Wael Hamdan


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[Squin-users] trying to use squin

[Seungbin Y. <li...@gm...>]

Hello,

My name is Seung-bin and I am trying to use squin for our project
called "web of needs".
http://researchstudio-sat.github.io/webofneeds/

I downloaded the sourcecode from the svn and try to build it, but without
luck.
It seems like that some commits are missing?
I get the following error message.
"cannot find symbol class UnboundedPrioritizedQueueImple" for the
ListenerRegistryImpl.java class.

Is it possible to fix this issue?

and I've seen that squin is built upon jena version of 2.6.2? is it correct?
Are there any known issues regarding compatiblity with newer jena versions?

Do you have any tips for us how we could use squin for our settings?
jena 2.11.0

Greetings,
Seung-bin

[Squin-users] ANN: SQUIN 0.1.4 released

[Olaf H. <ha...@in...>]

Hey,

I just put together a new version of SQUIN (0.1.4). The primary reason for 
this release was to upgrade SQUIN to the latest version of Jena (that is, 
version 2.7.0 with ARQ 2.9.0).

@Gustavo: You may want to use the command line interface ./bin/squin.sh from 
the standalone package. If you really want to use the ./bin/squin.sh in the 
source package, don't forget to adjust the JENA_LIBS variable to your 
environment (in ./bin/squin.sh). Please let me know whether it works for you 
now.

Cheers,
Olaf

Re: [Squin-users] Problems with Jena-2.7.0 and ARQ-2.9.0

[Olaf H. <ha...@in...>]

Hey Gustavo,

Sorry for the late reply! I'm very busy these days.

Anyways, I get the same error message when I (try to) use SQUIN with the 
latest version of ARQ. I will investigate the problem and post a fix as soon as 
possible.

Best,
Olaf


On Wednesday 16 May 2012 16:50:12 Gustavo Assis Costa wrote:
> Hi,
> 
> My name is Gustavo and I'm trying to start using SQUIN but I've had some
> problems. I suppose that it has happend because of the newest versions of
> Jena and ARQ, especially with the latter. Anyone here who has had this
> problem and could help me? I tried using the API through a code already
> posted here and I got the following error message:
> 
> 
> Exception in thread "main" java.lang.NoSuchMethodError:
> com.hp.hpl.jena.sparql.algebra.OpVars.allVars(Lcom/hp/hpl/jena/sparql/algebr
> a/Op;)Ljava/util/Set; at
> org.squin.dataset.query.arq.QueryEngine.initializeVarDictionary(QueryEngine.
> java:151) at
> org.squin.engine.LinkTraversalBasedQueryEngine.createExecutionContext(LinkTr
> aversalBasedQueryEngine.java:137) at
> org.squin.engine.LinkTraversalBasedQueryEngine.eval(LinkTraversalBasedQueryE
> ngine.java:126) at
> com.hp.hpl.jena.sparql.engine.QueryEngineBase.evaluate(QueryEngineBase.java:
> 129) at
> com.hp.hpl.jena.sparql.engine.QueryEngineBase.createPlan(QueryEngineBase.jav
> a:99) at
> com.hp.hpl.jena.sparql.engine.QueryEngineBase.getPlan(QueryEngineBase.java:8
> 7) at
> org.squin.engine.LinkTraversalBasedQueryEngineFactory.create(LinkTraversalBa
> sedQueryEngineFactory.java:54) at
> com.hp.hpl.jena.sparql.engine.QueryExecutionBase.getPlan(QueryExecutionBase.
> java:522) at
> com.hp.hpl.jena.sparql.engine.QueryExecutionBase.startQueryIterator(QueryExe
> cutionBase.java:499) at
> com.hp.hpl.jena.sparql.engine.QueryExecutionBase.execResultSet(QueryExecutio
> nBase.java:507) at
> com.hp.hpl.jena.sparql.engine.QueryExecutionBase.execSelect(QueryExecutionBa
> se.java:216) at lodproject.QueryLod.executeQuery(QueryLod.java:47)
> at lodproject.LODProject.main(LODProject.java:33)
> 
> 
> The source code:
> 
> 
> package lodproject;
> 
> import com.hp.hpl.jena.query.*;
> import java.util.concurrent.ExecutionException;
> import java.util.concurrent.TimeoutException;
> import org.squin.dataset.QueriedDataset;
> import org.squin.dataset.hashimpl.combined.QueriedDatasetImpl;
> import org.squin.dataset.jenacommon.JenaIOBasedQueriedDataset;
> import org.squin.engine.LinkTraversalBasedQueryEngine;
> import org.squin.engine.LinkedDataCacheWrappingDataset;
> import org.squin.ldcache.jenaimpl.JenaIOBasedLinkedDataCache;
> 
> /**
> *
> * @author Gustavo
> */
> public class QueryLod {
> 
>    static protected void executeQuery() {
> 
>        // Specify the query.
>        String queryString =
>        "PREFIX foaf: <http://xmlns.com/foaf/0.1/> " +
>        "SELECT DISTINCT ?i WHERE {" +
>        "<http://www.w3.org/People/Berners-Lee/card#i> foaf:knows ?p . " +
>        "?p foaf:interest ?i ." +
>        "}";
> 
>        QueryExecution qe;
>        JenaIOBasedLinkedDataCache ldcache = null;
>        try {
> 
>            LinkTraversalBasedQueryEngine.register();
> 
>            // create a Linked Data cache:
>            QueriedDataset qds = new QueriedDatasetImpl();
>            JenaIOBasedQueriedDataset qdsWrapper = new
> JenaIOBasedQueriedDataset( qds );
>            ldcache = new JenaIOBasedLinkedDataCache( qdsWrapper );
>            Dataset dsARQ = new LinkedDataCacheWrappingDataset( ldcache );
> 
>            Query query = QueryFactory.create(queryString);
>            qe = QueryExecutionFactory.create(query, dsARQ);
>            ResultSet results = qe.execSelect();
> 
>            // Output query results.
>            System.out.println("found " + results.getRowNumber() + " of
> matching triples!");
>            ResultSetFormatter.out(System.out, results);
>        }
>        catch(Exception e) {
>            System.out.println(e.getMessage());
>        }
>        finally {
>            try {
>                ldcache.shutdownNow( 4000 );
>            } catch (ExecutionException e) {
>                e.printStackTrace();
>            } catch (TimeoutException e) {
>                e.printStackTrace();
>            }
>        }
> 
>        System.out.println("\nall done.");
>    }
> }
> 
> Thanks !
> 
> ----------------------------------------------------------------------------
> -------------------- Gustavo de Assis Costa
> Doutorando em Engenharia Eletrônica e Computação - ITA (Brazil)
> E-mail: ga...@gm... ou gas...@it...
> ----------------------------------------------------------------------------
> --------------------

[Squin-users] Problems with Jena-2.7.0 and ARQ-2.9.0

[Gustavo A. C. <ga...@gm...>]

Hi,

My name is Gustavo and I'm trying to start using SQUIN but I've had some
problems. I suppose that it has happend because of the newest versions of
Jena and ARQ, especially with the latter. Anyone here who has had this
problem and could help me? I tried using the API through a code already
posted here and I got the following error message:


Exception in thread "main" java.lang.NoSuchMethodError:
com.hp.hpl.jena.sparql.algebra.OpVars.allVars(Lcom/hp/hpl/jena/sparql/algebra/Op;)Ljava/util/Set;
at
org.squin.dataset.query.arq.QueryEngine.initializeVarDictionary(QueryEngine.java:151)
at
org.squin.engine.LinkTraversalBasedQueryEngine.createExecutionContext(LinkTraversalBasedQueryEngine.java:137)
at
org.squin.engine.LinkTraversalBasedQueryEngine.eval(LinkTraversalBasedQueryEngine.java:126)
at
com.hp.hpl.jena.sparql.engine.QueryEngineBase.evaluate(QueryEngineBase.java:129)
at
com.hp.hpl.jena.sparql.engine.QueryEngineBase.createPlan(QueryEngineBase.java:99)
at
com.hp.hpl.jena.sparql.engine.QueryEngineBase.getPlan(QueryEngineBase.java:87)
at
org.squin.engine.LinkTraversalBasedQueryEngineFactory.create(LinkTraversalBasedQueryEngineFactory.java:54)
at
com.hp.hpl.jena.sparql.engine.QueryExecutionBase.getPlan(QueryExecutionBase.java:522)
at
com.hp.hpl.jena.sparql.engine.QueryExecutionBase.startQueryIterator(QueryExecutionBase.java:499)
at
com.hp.hpl.jena.sparql.engine.QueryExecutionBase.execResultSet(QueryExecutionBase.java:507)
at
com.hp.hpl.jena.sparql.engine.QueryExecutionBase.execSelect(QueryExecutionBase.java:216)
at lodproject.QueryLod.executeQuery(QueryLod.java:47)
at lodproject.LODProject.main(LODProject.java:33)


The source code:


package lodproject;

import com.hp.hpl.jena.query.*;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.TimeoutException;
import org.squin.dataset.QueriedDataset;
import org.squin.dataset.hashimpl.combined.QueriedDatasetImpl;
import org.squin.dataset.jenacommon.JenaIOBasedQueriedDataset;
import org.squin.engine.LinkTraversalBasedQueryEngine;
import org.squin.engine.LinkedDataCacheWrappingDataset;
import org.squin.ldcache.jenaimpl.JenaIOBasedLinkedDataCache;

/**
*
* @author Gustavo
*/
public class QueryLod {

   static protected void executeQuery() {

       // Specify the query.
       String queryString =
       "PREFIX foaf: <http://xmlns.com/foaf/0.1/> " +
       "SELECT DISTINCT ?i WHERE {" +
       "<http://www.w3.org/People/Berners-Lee/card#i> foaf:knows ?p . " +
       "?p foaf:interest ?i ." +
       "}";

       QueryExecution qe;
       JenaIOBasedLinkedDataCache ldcache = null;
       try {

           LinkTraversalBasedQueryEngine.register();

           // create a Linked Data cache:
           QueriedDataset qds = new QueriedDatasetImpl();
           JenaIOBasedQueriedDataset qdsWrapper = new
JenaIOBasedQueriedDataset( qds );
           ldcache = new JenaIOBasedLinkedDataCache( qdsWrapper );
           Dataset dsARQ = new LinkedDataCacheWrappingDataset( ldcache );

           Query query = QueryFactory.create(queryString);
           qe = QueryExecutionFactory.create(query, dsARQ);
           ResultSet results = qe.execSelect();

           // Output query results.
           System.out.println("found " + results.getRowNumber() + " of
matching triples!");
           ResultSetFormatter.out(System.out, results);
       }
       catch(Exception e) {
           System.out.println(e.getMessage());
       }
       finally {
           try {
               ldcache.shutdownNow( 4000 );
           } catch (ExecutionException e) {
               e.printStackTrace();
           } catch (TimeoutException e) {
               e.printStackTrace();
           }
       }

       System.out.println("\nall done.");
   }
}

Thanks !

------------------------------------------------------------------------------------------------
Gustavo de Assis Costa
Doutorando em Engenharia Eletrônica e Computação - ITA (Brazil)
E-mail: ga...@gm... ou gas...@it...
------------------------------------------------------------------------------------------------

Re: [Squin-users] link traversal using models

[Urs H. <ur...@an...>]

Hi Olaf

Olaf Hartig wrote:
> [...]
> * Create a 'JenaIOBasedLinkedDataCache' object.
> 
> * This cache object has a 'asJenaGraph' method with which you may get
> a wrapper around the cache in form of an implementation of the Jena
> 'Graph' interface. You may want to use this 'Graph' to create a Jena
> 'Model'.
> 
> * Via the method(s) 'ensureAvailability' of the cache object you may
> initiate URI lookups that are performed in an asynchronous thread in
> the background. Note, you may want to use the 'ensureAvailability'
> methods that have a Jena 'Node' object as second parameter. These
> methods are not in the 'LinkedDataCache' but in the
> 'JenaIOBasedLinkedDataCache' class.
> 
> * When an asynchronous URI lookup has been completed (successfully),
> the retrieved data should be automatically be part of the Jena
> 'Graph' that you created by calling 'asJenaGraph'.

Excellent! It works perfectly. It is fun to watch the GUI of my 
application build up as the asynchronous lookups complete.

Greetings
Urs

Re: [Squin-users] link traversal using models

[Olaf H. <ha...@in...>]

Dear Urs,

With SQUIN, I indeed try to focus on providing a (link traversal based) query 
system. However, the code may also be used as some kind of a library that 
provides all components necessary for i) implementing link traversal based 
algorithms or ii) a Jena model that may continuously grow as a result of URI 
lookups initiated by application code. I guess you are primarily interested in 
the latter. This can be achieved as follows:

* Create a 'JenaIOBasedLinkedDataCache' object.

* This cache object has a 'asJenaGraph' method with which you may get a 
wrapper around the cache in form of an implementation of the Jena 'Graph' 
interface. You may want to use this 'Graph' to create a Jena 'Model'.

* Via the method(s) 'ensureAvailability' of the cache object you may initiate 
URI lookups that are performed in an asynchronous thread in the background. 
Note, you may want to use the 'ensureAvailability' methods that have a Jena 
'Node' object as second parameter. These methods are not in the 
'LinkedDataCache' but in the 'JenaIOBasedLinkedDataCache' class.

* When an asynchronous URI lookup has been completed (successfully), the 
retrieved data should be automatically be part of the Jena 'Graph' that you 
created by calling 'asJenaGraph'.

I hope that helps.

Cheers,
Olaf


On Saturday 24 March 2012 16:16:58 Urs Holzer wrote:
> Hi
> 
> Since quite a long time I am fascinated by the semantic web. Now I
> decided to write a small tool to manage my own knowledge (about tools,
> libraries, papers, websites, friends). I started with ng4j and the
> semantic web client library. Now I am trying to switch to SQUIN.
> 
> I do not know much about Jena nor about SQUIN at this point, so I wonder
> how I should continue. Therefore I have some questions and let me start
> with this issue:
> 
> With the semantic web client library it is possible to have a Jena model
> which does link traversal in the background. Say, if you ask it about
> some resource, it fetches information about this resource from the web.
> Is it with SQUIN possible to create a model which behaves the same way
> or does SQUIN only fetch more information from the web when executing
> SPARQL queries?
> (Actually, I tried to use a default model obtained from a
> LinkedDataCacheWrappingDataset, but it only seems to act on the union of
> all graphs from the Dataset without fetching more graphs.)
> 
> More about my tool:
> It will allow me to quickly take semantic notes. For this I need to be
> able to quickly discover the resources I want to make statements about.
> Let's say I discover http://squin.org/ which is relevant to
> one of my projects. In this case I have to:
> - Find the resource representing my project
> - Find a property for "is relevant"
> - Fetch metadata about http://squin.org/
> - If I was unable to find metadata I have to find a resource for its
> topic manually, say by searching with Sindice for "Semantic Web" or in
> this case, by searching for "Semantic Web" in my local graphs only.
> - Decide into which graph I want to put which statements and serialize
> the graph.
> Of course, after this, I will be able to look up all my firends who are
> interested in the same topic and send them spam about my new discovery.
> 
> Greetings
> Urs
> 
> ----------------------------------------------------------------------------
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[Squin-users] link traversal using models

[Urs H. <ur...@an...>]

Hi

Since quite a long time I am fascinated by the semantic web. Now I 
decided to write a small tool to manage my own knowledge (about tools, 
libraries, papers, websites, friends). I started with ng4j and the 
semantic web client library. Now I am trying to switch to SQUIN.

I do not know much about Jena nor about SQUIN at this point, so I wonder 
how I should continue. Therefore I have some questions and let me start 
with this issue:

With the semantic web client library it is possible to have a Jena model 
which does link traversal in the background. Say, if you ask it about 
some resource, it fetches information about this resource from the web. 
Is it with SQUIN possible to create a model which behaves the same way 
or does SQUIN only fetch more information from the web when executing 
SPARQL queries? 
(Actually, I tried to use a default model obtained from a 
LinkedDataCacheWrappingDataset, but it only seems to act on the union of 
all graphs from the Dataset without fetching more graphs.)

More about my tool:
It will allow me to quickly take semantic notes. For this I need to be 
able to quickly discover the resources I want to make statements about. 
Let's say I discover http://squin.org/ which is relevant to 
one of my projects. In this case I have to:
- Find the resource representing my project
- Find a property for "is relevant"
- Fetch metadata about http://squin.org/
- If I was unable to find metadata I have to find a resource for its 
topic manually, say by searching with Sindice for "Semantic Web" or in 
this case, by searching for "Semantic Web" in my local graphs only.
- Decide into which graph I want to put which statements and serialize 
the graph.
Of course, after this, I will be able to look up all my firends who are 
interested in the same topic and send them spam about my new discovery.

Greetings
Urs

[Squin-users] ANN: SQUIN 0.1.2 - no dependency on NG4J anymore

[Olaf H. <ha...@in...>]

Hey,

I just released version 0.1.2 of SQUIN. 

I developed a new, independent component for URI dereferencing and,
thus, replaced the last bits of code that were depending on functionality 
implemented in the Semantic Web Client Library. Hence, with this release, 
SQUIN becomes completely independent of NG4J.

You find the latest source code as well as a stand-alone install package on the 
SQUIN Web site at:

                          http://squin.org

Cheers,
Olaf

Re: [Squin-users] exception happens on this line: Dataset dsARQ = new LinkedDataCacheWrappingDataset( ldcache );

[l Yu <wy...@gm...>]

Dear Olaf,

Great catch!!! I cannot believe I missed that part - I recently changed my
web-hosting company, and I did not have a chance to change the Application
content type. thank you so much!!!

the original query works very well,

        String queryString =
            "PREFIX foaf: <http://xmlns.com/foaf/0.1/> " +
            "PREFIX dc: <http://purl.org/dc/elements/1.1/> " +
            "SELECT * " +
            "WHERE { " +
            "   <http://www.liyangyu.com/foaf.rdf#liyang> foaf:made ?book .
" +
            "   ?book dc:title ?title . " +
            "   ?book dc:identifier ?isbn }";


and here is the output:

---------------------------------------------------------------------------------------------------------------------------------------------------------
| book                                                          |
title                                                         |
isbn                  |
=========================================================================================================================================================
| <http://www4.wiwiss.fu-berlin.de/bookmashup/books/3642159699> | "A
Developer's Guide to the Semantic Web"                     |
<urn:ISBN:3642159699> |
| <http://www4.wiwiss.fu-berlin.de/bookmashup/books/1584889330> |
"Introduction to the Semantic  Web and Semantic Web Services" |
<urn:ISBN:1584889330> |
---------------------------------------------------------------------------------------------------------------------------------------------------------

thank you again for you nice work!!


On Wed, May 4, 2011 at 12:45 PM, Olaf Hartig <ha...@in...
> wrote:

> Hey liyang,
>
> I found the reason for the problem that you reported. The issue with
> queries
> that contain the URI
>
>  http://www.liyangyu.com/foaf.rdf#liyang
>
> is the following: When I dereference that URI using the HTTP protocol, the
> server, indeed, provides the RDF/XML serialization that you copied to your
> mail, but -according to the HTTP header with which the server responds-
> that
> document is of type text/html.
> You can try that yourself. On the command line use curl to GET an RDF/XML
> representation of the URI:
>
> curl -i -H "Accept: application/rdf+xml" http://www.liyangyu.com/foaf.rdf
>
> ... and you will see, the response says that the Content-Type is text/html:
>
> HTTP/1.1 200 OK
> Date: Wed, 04 May 2011 16:34:43 GMT
> Content-Type: text/html
> Connection: keep-alive
> Server: Apache/Nginx/Varnish
> Last-Modified: Wed, 04 May 2011 13:14:36 GMT
> ETag: "84e260-57b-4a27309d16b3c"
> Accept-Ranges: bytes
> Content-Length: 1403
>
> <?xml version="1.0" encoding="UTF-8"?>
> <rdf:RDF
>      xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
>      xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#"
>      xmlns:dc="http://purl.org/dc/elements/1.1/"
> ---- snip ----
>
>
> Now, when the 'lookup.deref' component of SQUIN retrieves something that is
> said to be text/html, then it tries to parse the content as if it were an
> HTML
> document. Obviously, that fails for an RDF/XML serialization and, thus,
> dereferencing the URI results in a failure. Therefore, the data from the
> FOAF
> profile does not end up in the query-local dataset of SQUIN and, thus,
> cannot
> be used for triple pattern matching.
>
> Hence, the problem in this case is actually a misbehaving HTTP server at
> www.liyangyu.com
>
> Hope that helps,
> Olaf
>
>
> On Wednesday 04 May 2011 18:11:23 l Yu wrote:
> > Dear Olaf,
> >
> > Thank you so much for the help  - yes, *it is indeed the version
> problem*,
> > once I switched to the right versions, it worked.
> >
> > However, it worked *only *for the examples on your Web site, for
> instance,
> > this query works:
> >
> > String queryString =
> >         "PREFIX foaf: <http://xmlns.com/foaf/0.1/> " +
> >         "SELECT DISTINCT ?i WHERE {" +
> >         "<http://www.w3.org/People/Berners-Lee/card#i> foaf:knows ?p . "
> +
> >         "?p foaf:interest ?i ." +
> >         "}";
> >
> > For* our own query, it still does not work*:
> >
> > Here is our query:
> >
> >         String queryString =
> >             "PREFIX foaf: <http://xmlns.com/foaf/0.1/> " +
> >             "PREFIX dc: <http://purl.org/dc/elements/1.1/> " +
> >             "SELECT * " +
> >             "WHERE { " +
> >             "   <*http://www.liyangyu.com/foaf.rdf#liyang*> foaf:made
> ?book
> > . " +
> >             "   ?book dc:title ?title . " +
> >             "   ?book dc:identifier ?isbn }";
> >
> >
> > If you dereferencing http://www.liyangyu.com/foaf.rdf#liyang, you can
> get
> > the following back,
> >
> > <?xml version="1.0" encoding="UTF-8"?>
> > <rdf:RDF
> >       xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
> >       xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#"
> >       xmlns:dc="http://purl.org/dc/elements/1.1/"
> >       xmlns:owl="http://www.w3.org/2002/07/owl#"
> >       xmlns:foaf="http://xmlns.com/foaf/0.1/">
> >
> > <rdf:Description rdf:about="http://www.liyangyu.com/foaf.rdf#liyang">
> >    <foaf:name>liyang yu</foaf:name>
> >
> >    <foaf:title>Dr</foaf:title>
> >    <foaf:givenname>liyang</foaf:givenname>
> >    <foaf:family_name>yu</foaf:family_name>
> >
> >
> >
> <foaf:mbox_sha1sum>1613a9c3ec8b18271a8fe1f79537a7b08803d896</foaf:mbox_sha
> > 1sum> <foaf:homepage rdf:resource="http://www.liyangyu.com"/>
> >    <foaf:workplaceHomepage rdf:resource="http://www.delta.com"/>
> >    <rdf:type rdf:resource="http://xmlns.com/foaf/0.1/Person"/>
> >
> > *   <foaf:made
> > rdf:resource="
> http://www4.wiwiss.fu-berlin.de/bookmashup/books/3642159699"
> > /> <foaf:made
> > rdf:resource="
> http://www4.wiwiss.fu-berlin.de/bookmashup/books/1584889330"
> > />*
> >
> >    <foaf:knows>
> >
> >       <!-- the following is for testing purpose -->
> >       <foaf:Person>
> >          <foaf:name>Roger Federer</foaf:name>
> >          <owl:sameAs
> > rdf:resource="http://dbpedia.org/resource/Roger_Federer"/>
> </foaf:Person>
> >    </foaf:knows>
> >
> >    <foaf:topic_interest
> > rdf:resource="http://dbpedia.org/resource/Semantic_Web"/>
> >
> > </rdf:Description>
> >
> >
> > </rdf:RDF>
> >
> >
> > The *red lines* should be the matching triples, and then it should be
> able
> > to deference the book URI and find the title and ISBN of the book (RDF
> Book
> > Mashup). However, it does not work.
> >
> > In fact, *even the simplest query like this will not work at all:*
> >
> >         String queryString =
> >             "PREFIX foaf: <http://xmlns.com/foaf/0.1/> " +
> >             "PREFIX dc: <http://purl.org/dc/elements/1.1/> " +
> >             "SELECT * " +
> >             "WHERE { " +
> >             "   <http://www.liyangyu.com/foaf.rdf#liyang> foaf:name
> ?myName
> > } ";
> >
> >
> > Could you please kindly take a look (*the following is the complete code
> > you can test*). We must have missed something - it should work for a
> > simple query like above....
> >
> > import java.util.concurrent.ExecutionException;
> > import java.util.concurrent.TimeoutException;
> >
> > import org.squin.dataset.QueriedDataset;
> > import org.squin.dataset.hashimpl.combined.QueriedDatasetImpl;
> > import org.squin.dataset.jenacommon.JenaIOBasedQueriedDataset;
> > import org.squin.engine.LinkTraversalBasedQueryEngine;
> > import org.squin.engine.LinkedDataCacheWrappingDataset;
> > import org.squin.ldcache.jenaimpl.JenaIOBasedLinkedDataCache;
> > import org.squin.ldcache.ng4jimpl.SWClLibBasedLinkedDataCache;
> >
> > import com.hp.hpl.jena.query.Dataset;
> > import com.hp.hpl.jena.query.QueryExecution;
> > import com.hp.hpl.jena.query.QueryExecutionFactory;
> > import com.hp.hpl.jena.query.ResultSet;
> > import com.hp.hpl.jena.query.ResultSetFormatter;
> >
> > public class AutomaticLinkTraversalExample {
> >
> >     public static void main(String[] args) {
> >
> >         // Specify the query.
> >         /*String queryString =
> >         "PREFIX foaf: <http://xmlns.com/foaf/0.1/> " +
> >         "SELECT DISTINCT ?i WHERE {" +
> >         "<http://www.w3.org/People/Berners-Lee/card#i> foaf:knows ?p . "
> +
> >         "?p foaf:interest ?i ." +
> >         "}"; */
> >
> >         String queryString =
> >             "PREFIX foaf: <http://xmlns.com/foaf/0.1/> " +
> >             "PREFIX dc: <http://purl.org/dc/elements/1.1/> " +
> >             "SELECT * " +
> >             "WHERE { " +
> >             "   <http://www.liyangyu.com/foaf.rdf#liyang> foaf:name
> ?myName
> > } ";
> >
> >         QueryExecution qe = null;
> >         JenaIOBasedLinkedDataCache ldcache = null;
> >         try {
> >
> >             LinkTraversalBasedQueryEngine.register();
> >
> >             // create a Linked Data cache:
> >             QueriedDataset qds = new QueriedDatasetImpl();
> >             JenaIOBasedQueriedDataset qdsWrapper = new
> > JenaIOBasedQueriedDataset( qds );
> >             ldcache = new SWClLibBasedLinkedDataCache( qdsWrapper );
> >             Dataset dsARQ = new LinkedDataCacheWrappingDataset( ldcache
> );
> >
> >             qe = QueryExecutionFactory.create(queryString, dsARQ);
> >             ResultSet results = qe.execSelect();
> >
> >             // Output query results.
> >             System.out.println("found " + results.getRowNumber() + " of
> > matching triples!");
> >             ResultSetFormatter.out(System.out, results);
> >         }
> >         catch(Exception e) {
> >             System.out.println(e.getMessage());
> >         }
> >         finally {
> >             try {
> >                 ldcache.shutdownNow( 4000 );
> >             } catch (ExecutionException e) {
> >                 e.printStackTrace();
> >             } catch (TimeoutException e) {
> >                 e.printStackTrace();
> >             }
> >         }
> >
> >         System.out.println("\nall done.");
> >     }
> > }
> >
> > Thank you for the help!!
> >
> > liyang
> >
> > On Wed, May 4, 2011 at 5:28 AM, Olaf Hartig
> >
> > <ha...@in...>wrote:
> > > Hey liyang,
> > >
> > > First, I found and fixed a small bug (which had nothing to do with the
> > > problem
> > > you reported). I released a new version of SQUIN: 0.1.1
> > >
> > > On 2011-05-04 00:25 l Yu <wyriwyg@gm...> wrote:
> > > > just a thought: which Jena version we should be using together with
> the
> > > > squin-0.1.0.jar file? could it be the version of Jean (ARQ) is not
> > >
> > > correct?
> > >
> > > > On Tue, May 3, 2011 at 8:20 PM, l Yu <wyriwyg@...> wrote:
> > > >> Hi,
> > >
> > > [...]
> > >
> > > >> The red line throws an exception like this:
> > > >>
> > > >> Exception in thread "main" java.lang.VerifyError: class
> > > >> org.squin.engine.LinkedDataCacheWrappingDatasetGraph overrides final
> > >
> > > method
> > >
> > > >> getDefaultGraph.()Lcom/hp/hpl/jena/graph/Graph;
> > >
> > > [...]
> > >
> > > I tested the code you posted with SQUIN 0.1.1 on my system and it
> works;
> > > i.e. I did not get the exception that you got.
> > >
> > > I assume -as you suggest- that the problem is caused by using an old
> > > Jena/ARQ.
> > > As it says in the README.txt, SQUIN 0.1.1 must be used with the
> libraries
> > > from
> > > the current CVS checkout of the NG4J project. Hence, you must not only
> > > compile
> > > your application (or SQUIN itself) with these libraries but you must
> also
> > > use
> > > these libraries to run your application. The versions of Jena and ARQ
> > > that you
> > > find in the CVS of NG4J are 2.6.4 and 2.8.8, respectively.
> > >
> > > Sorry for the inconvenience of requiring the NG4J CVS. I will try to
> get
> > > rid
> > > of that dependency as soon as possible.
> > >
> > > BTW, as an alternative you may download the SQUIN Standalone package
> > > which contains all necessary libraries in the ./lib/ext/ directory.
> > > Hence, you
> > > may use the content of that directory for your CLASSPATH.
> > >
> > > Greetings,
> > > Olaf
> > >
> > >
> > >
> -------------------------------------------------------------------------
> > > ----- WhatsUp Gold - Download Free Network Management Software
> > > The most intuitive, comprehensive, and cost-effective network
> > > management toolset available today.  Delivers lowest initial
> > > acquisition cost and overall TCO of any competing solution.
> > > http://p.sf.net/sfu/whatsupgold-sd
> > > _______________________________________________
> > > Squin-users mailing list
> > > Squ...@li...
> > > https://lists.sourceforge.net/lists/listinfo/squin-users
>
>
> ------------------------------------------------------------------------------
> WhatsUp Gold - Download Free Network Management Software
> The most intuitive, comprehensive, and cost-effective network
> management toolset available today.  Delivers lowest initial
> acquisition cost and overall TCO of any competing solution.
> http://p.sf.net/sfu/whatsupgold-sd
> _______________________________________________
> Squin-users mailing list
> Squ...@li...
> https://lists.sourceforge.net/lists/listinfo/squin-users
>

Re: [Squin-users] exception happens on this line: Dataset dsARQ = new LinkedDataCacheWrappingDataset( ldcache );

[Olaf H. <ha...@in...>]

Hey liyang,

I found the reason for the problem that you reported. The issue with queries 
that contain the URI

  http://www.liyangyu.com/foaf.rdf#liyang 

is the following: When I dereference that URI using the HTTP protocol, the 
server, indeed, provides the RDF/XML serialization that you copied to your 
mail, but -according to the HTTP header with which the server responds- that 
document is of type text/html.
You can try that yourself. On the command line use curl to GET an RDF/XML 
representation of the URI:

curl -i -H "Accept: application/rdf+xml" http://www.liyangyu.com/foaf.rdf

... and you will see, the response says that the Content-Type is text/html:

HTTP/1.1 200 OK
Date: Wed, 04 May 2011 16:34:43 GMT
Content-Type: text/html
Connection: keep-alive
Server: Apache/Nginx/Varnish
Last-Modified: Wed, 04 May 2011 13:14:36 GMT
ETag: "84e260-57b-4a27309d16b3c"
Accept-Ranges: bytes
Content-Length: 1403

<?xml version="1.0" encoding="UTF-8"?>
<rdf:RDF
      xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
      xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#"
      xmlns:dc="http://purl.org/dc/elements/1.1/"
---- snip ----


Now, when the 'lookup.deref' component of SQUIN retrieves something that is 
said to be text/html, then it tries to parse the content as if it were an HTML 
document. Obviously, that fails for an RDF/XML serialization and, thus, 
dereferencing the URI results in a failure. Therefore, the data from the FOAF 
profile does not end up in the query-local dataset of SQUIN and, thus, cannot 
be used for triple pattern matching.

Hence, the problem in this case is actually a misbehaving HTTP server at 
www.liyangyu.com

Hope that helps,
Olaf


On Wednesday 04 May 2011 18:11:23 l Yu wrote:
> Dear Olaf,
> 
> Thank you so much for the help  - yes, *it is indeed the version problem*,
> once I switched to the right versions, it worked.
> 
> However, it worked *only *for the examples on your Web site, for instance,
> this query works:
> 
> String queryString =
>         "PREFIX foaf: <http://xmlns.com/foaf/0.1/> " +
>         "SELECT DISTINCT ?i WHERE {" +
>         "<http://www.w3.org/People/Berners-Lee/card#i> foaf:knows ?p . " +
>         "?p foaf:interest ?i ." +
>         "}";
> 
> For* our own query, it still does not work*:
> 
> Here is our query:
> 
>         String queryString =
>             "PREFIX foaf: <http://xmlns.com/foaf/0.1/> " +
>             "PREFIX dc: <http://purl.org/dc/elements/1.1/> " +
>             "SELECT * " +
>             "WHERE { " +
>             "   <*http://www.liyangyu.com/foaf.rdf#liyang*> foaf:made ?book
> . " +
>             "   ?book dc:title ?title . " +
>             "   ?book dc:identifier ?isbn }";
> 
> 
> If you dereferencing http://www.liyangyu.com/foaf.rdf#liyang, you can get
> the following back,
> 
> <?xml version="1.0" encoding="UTF-8"?>
> <rdf:RDF
>       xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
>       xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#"
>       xmlns:dc="http://purl.org/dc/elements/1.1/"
>       xmlns:owl="http://www.w3.org/2002/07/owl#"
>       xmlns:foaf="http://xmlns.com/foaf/0.1/">
> 
> <rdf:Description rdf:about="http://www.liyangyu.com/foaf.rdf#liyang">
>    <foaf:name>liyang yu</foaf:name>
> 
>    <foaf:title>Dr</foaf:title>
>    <foaf:givenname>liyang</foaf:givenname>
>    <foaf:family_name>yu</foaf:family_name>
> 
>   
> <foaf:mbox_sha1sum>1613a9c3ec8b18271a8fe1f79537a7b08803d896</foaf:mbox_sha
> 1sum> <foaf:homepage rdf:resource="http://www.liyangyu.com"/>
>    <foaf:workplaceHomepage rdf:resource="http://www.delta.com"/>
>    <rdf:type rdf:resource="http://xmlns.com/foaf/0.1/Person"/>
> 
> *   <foaf:made
> rdf:resource="http://www4.wiwiss.fu-berlin.de/bookmashup/books/3642159699"
> /> <foaf:made
> rdf:resource="http://www4.wiwiss.fu-berlin.de/bookmashup/books/1584889330"
> />*
> 
>    <foaf:knows>
> 
>       <!-- the following is for testing purpose -->
>       <foaf:Person>
>          <foaf:name>Roger Federer</foaf:name>
>          <owl:sameAs
> rdf:resource="http://dbpedia.org/resource/Roger_Federer"/> </foaf:Person>
>    </foaf:knows>
> 
>    <foaf:topic_interest
> rdf:resource="http://dbpedia.org/resource/Semantic_Web"/>
> 
> </rdf:Description>
> 
> 
> </rdf:RDF>
> 
> 
> The *red lines* should be the matching triples, and then it should be able
> to deference the book URI and find the title and ISBN of the book (RDF Book
> Mashup). However, it does not work.
> 
> In fact, *even the simplest query like this will not work at all:*
> 
>         String queryString =
>             "PREFIX foaf: <http://xmlns.com/foaf/0.1/> " +
>             "PREFIX dc: <http://purl.org/dc/elements/1.1/> " +
>             "SELECT * " +
>             "WHERE { " +
>             "   <http://www.liyangyu.com/foaf.rdf#liyang> foaf:name ?myName
> } ";
> 
> 
> Could you please kindly take a look (*the following is the complete code
> you can test*). We must have missed something - it should work for a
> simple query like above....
> 
> import java.util.concurrent.ExecutionException;
> import java.util.concurrent.TimeoutException;
> 
> import org.squin.dataset.QueriedDataset;
> import org.squin.dataset.hashimpl.combined.QueriedDatasetImpl;
> import org.squin.dataset.jenacommon.JenaIOBasedQueriedDataset;
> import org.squin.engine.LinkTraversalBasedQueryEngine;
> import org.squin.engine.LinkedDataCacheWrappingDataset;
> import org.squin.ldcache.jenaimpl.JenaIOBasedLinkedDataCache;
> import org.squin.ldcache.ng4jimpl.SWClLibBasedLinkedDataCache;
> 
> import com.hp.hpl.jena.query.Dataset;
> import com.hp.hpl.jena.query.QueryExecution;
> import com.hp.hpl.jena.query.QueryExecutionFactory;
> import com.hp.hpl.jena.query.ResultSet;
> import com.hp.hpl.jena.query.ResultSetFormatter;
> 
> public class AutomaticLinkTraversalExample {
> 
>     public static void main(String[] args) {
> 
>         // Specify the query.
>         /*String queryString =
>         "PREFIX foaf: <http://xmlns.com/foaf/0.1/> " +
>         "SELECT DISTINCT ?i WHERE {" +
>         "<http://www.w3.org/People/Berners-Lee/card#i> foaf:knows ?p . " +
>         "?p foaf:interest ?i ." +
>         "}"; */
> 
>         String queryString =
>             "PREFIX foaf: <http://xmlns.com/foaf/0.1/> " +
>             "PREFIX dc: <http://purl.org/dc/elements/1.1/> " +
>             "SELECT * " +
>             "WHERE { " +
>             "   <http://www.liyangyu.com/foaf.rdf#liyang> foaf:name ?myName
> } ";
> 
>         QueryExecution qe = null;
>         JenaIOBasedLinkedDataCache ldcache = null;
>         try {
> 
>             LinkTraversalBasedQueryEngine.register();
> 
>             // create a Linked Data cache:
>             QueriedDataset qds = new QueriedDatasetImpl();
>             JenaIOBasedQueriedDataset qdsWrapper = new
> JenaIOBasedQueriedDataset( qds );
>             ldcache = new SWClLibBasedLinkedDataCache( qdsWrapper );
>             Dataset dsARQ = new LinkedDataCacheWrappingDataset( ldcache );
> 
>             qe = QueryExecutionFactory.create(queryString, dsARQ);
>             ResultSet results = qe.execSelect();
> 
>             // Output query results.
>             System.out.println("found " + results.getRowNumber() + " of
> matching triples!");
>             ResultSetFormatter.out(System.out, results);
>         }
>         catch(Exception e) {
>             System.out.println(e.getMessage());
>         }
>         finally {
>             try {
>                 ldcache.shutdownNow( 4000 );
>             } catch (ExecutionException e) {
>                 e.printStackTrace();
>             } catch (TimeoutException e) {
>                 e.printStackTrace();
>             }
>         }
> 
>         System.out.println("\nall done.");
>     }
> }
> 
> Thank you for the help!!
> 
> liyang
> 
> On Wed, May 4, 2011 at 5:28 AM, Olaf Hartig
> 
> <ha...@in...>wrote:
> > Hey liyang,
> > 
> > First, I found and fixed a small bug (which had nothing to do with the
> > problem
> > you reported). I released a new version of SQUIN: 0.1.1
> > 
> > On 2011-05-04 00:25 l Yu <wyriwyg@gm...> wrote:
> > > just a thought: which Jena version we should be using together with the
> > > squin-0.1.0.jar file? could it be the version of Jean (ARQ) is not
> > 
> > correct?
> > 
> > > On Tue, May 3, 2011 at 8:20 PM, l Yu <wyriwyg@...> wrote:
> > >> Hi,
> > 
> > [...]
> > 
> > >> The red line throws an exception like this:
> > >> 
> > >> Exception in thread "main" java.lang.VerifyError: class
> > >> org.squin.engine.LinkedDataCacheWrappingDatasetGraph overrides final
> > 
> > method
> > 
> > >> getDefaultGraph.()Lcom/hp/hpl/jena/graph/Graph;
> > 
> > [...]
> > 
> > I tested the code you posted with SQUIN 0.1.1 on my system and it works;
> > i.e. I did not get the exception that you got.
> > 
> > I assume -as you suggest- that the problem is caused by using an old
> > Jena/ARQ.
> > As it says in the README.txt, SQUIN 0.1.1 must be used with the libraries
> > from
> > the current CVS checkout of the NG4J project. Hence, you must not only
> > compile
> > your application (or SQUIN itself) with these libraries but you must also
> > use
> > these libraries to run your application. The versions of Jena and ARQ
> > that you
> > find in the CVS of NG4J are 2.6.4 and 2.8.8, respectively.
> > 
> > Sorry for the inconvenience of requiring the NG4J CVS. I will try to get
> > rid
> > of that dependency as soon as possible.
> > 
> > BTW, as an alternative you may download the SQUIN Standalone package
> > which contains all necessary libraries in the ./lib/ext/ directory.
> > Hence, you
> > may use the content of that directory for your CLASSPATH.
> > 
> > Greetings,
> > Olaf
> > 
> > 
> > -------------------------------------------------------------------------
> > ----- WhatsUp Gold - Download Free Network Management Software
> > The most intuitive, comprehensive, and cost-effective network
> > management toolset available today.  Delivers lowest initial
> > acquisition cost and overall TCO of any competing solution.
> > http://p.sf.net/sfu/whatsupgold-sd
> > _______________________________________________
> > Squin-users mailing list
> > Squ...@li...
> > https://lists.sourceforge.net/lists/listinfo/squin-users

Re: [Squin-users] exception happens on this line: Dataset dsARQ = new LinkedDataCacheWrappingDataset( ldcache );

[l Yu <wy...@gm...>]

Dear Olaf,

Thank you so much for the help  - yes, *it is indeed the version problem*,
once I switched to the right versions, it worked.

However, it worked *only *for the examples on your Web site, for instance,
this query works:

String queryString =
        "PREFIX foaf: <http://xmlns.com/foaf/0.1/> " +
        "SELECT DISTINCT ?i WHERE {" +
        "<http://www.w3.org/People/Berners-Lee/card#i> foaf:knows ?p . " +
        "?p foaf:interest ?i ." +
        "}";

For* our own query, it still does not work*:

Here is our query:

        String queryString =
            "PREFIX foaf: <http://xmlns.com/foaf/0.1/> " +
            "PREFIX dc: <http://purl.org/dc/elements/1.1/> " +
            "SELECT * " +
            "WHERE { " +
            "   <*http://www.liyangyu.com/foaf.rdf#liyang*> foaf:made ?book
. " +
            "   ?book dc:title ?title . " +
            "   ?book dc:identifier ?isbn }";


If you dereferencing http://www.liyangyu.com/foaf.rdf#liyang, you can get
the following back,

<?xml version="1.0" encoding="UTF-8"?>
<rdf:RDF
      xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
      xmlns:rdfs="http://www.w3.org/2000/01/rdf-schema#"
      xmlns:dc="http://purl.org/dc/elements/1.1/"
      xmlns:owl="http://www.w3.org/2002/07/owl#"
      xmlns:foaf="http://xmlns.com/foaf/0.1/">

<rdf:Description rdf:about="http://www.liyangyu.com/foaf.rdf#liyang">
   <foaf:name>liyang yu</foaf:name>

   <foaf:title>Dr</foaf:title>
   <foaf:givenname>liyang</foaf:givenname>
   <foaf:family_name>yu</foaf:family_name>

   <foaf:mbox_sha1sum>1613a9c3ec8b18271a8fe1f79537a7b08803d896</foaf:mbox_sha1sum>
   <foaf:homepage rdf:resource="http://www.liyangyu.com"/>
   <foaf:workplaceHomepage rdf:resource="http://www.delta.com"/>
   <rdf:type rdf:resource="http://xmlns.com/foaf/0.1/Person"/>

*   <foaf:made rdf:resource="http://www4.wiwiss.fu-berlin.de/bookmashup/books/3642159699"/>
   <foaf:made rdf:resource="http://www4.wiwiss.fu-berlin.de/bookmashup/books/1584889330"/>*

   <foaf:knows>

      <!-- the following is for testing purpose -->
      <foaf:Person>
         <foaf:name>Roger Federer</foaf:name>
         <owl:sameAs rdf:resource="http://dbpedia.org/resource/Roger_Federer"/>
      </foaf:Person>
   </foaf:knows>

   <foaf:topic_interest
rdf:resource="http://dbpedia.org/resource/Semantic_Web"/>

</rdf:Description>


</rdf:RDF>


The *red lines* should be the matching triples, and then it should be able
to deference the book URI and find the title and ISBN of the book (RDF Book
Mashup). However, it does not work.

In fact, *even the simplest query like this will not work at all:*

        String queryString =
            "PREFIX foaf: <http://xmlns.com/foaf/0.1/> " +
            "PREFIX dc: <http://purl.org/dc/elements/1.1/> " +
            "SELECT * " +
            "WHERE { " +
            "   <http://www.liyangyu.com/foaf.rdf#liyang> foaf:name ?myName
} ";


Could you please kindly take a look (*the following is the complete code you
can test*). We must have missed something - it should work for a simple
query like above....

import java.util.concurrent.ExecutionException;
import java.util.concurrent.TimeoutException;

import org.squin.dataset.QueriedDataset;
import org.squin.dataset.hashimpl.combined.QueriedDatasetImpl;
import org.squin.dataset.jenacommon.JenaIOBasedQueriedDataset;
import org.squin.engine.LinkTraversalBasedQueryEngine;
import org.squin.engine.LinkedDataCacheWrappingDataset;
import org.squin.ldcache.jenaimpl.JenaIOBasedLinkedDataCache;
import org.squin.ldcache.ng4jimpl.SWClLibBasedLinkedDataCache;

import com.hp.hpl.jena.query.Dataset;
import com.hp.hpl.jena.query.QueryExecution;
import com.hp.hpl.jena.query.QueryExecutionFactory;
import com.hp.hpl.jena.query.ResultSet;
import com.hp.hpl.jena.query.ResultSetFormatter;

public class AutomaticLinkTraversalExample {

    public static void main(String[] args) {

        // Specify the query.
        /*String queryString =
        "PREFIX foaf: <http://xmlns.com/foaf/0.1/> " +
        "SELECT DISTINCT ?i WHERE {" +
        "<http://www.w3.org/People/Berners-Lee/card#i> foaf:knows ?p . " +
        "?p foaf:interest ?i ." +
        "}"; */

        String queryString =
            "PREFIX foaf: <http://xmlns.com/foaf/0.1/> " +
            "PREFIX dc: <http://purl.org/dc/elements/1.1/> " +
            "SELECT * " +
            "WHERE { " +
            "   <http://www.liyangyu.com/foaf.rdf#liyang> foaf:name ?myName
} ";

        QueryExecution qe = null;
        JenaIOBasedLinkedDataCache ldcache = null;
        try {

            LinkTraversalBasedQueryEngine.register();

            // create a Linked Data cache:
            QueriedDataset qds = new QueriedDatasetImpl();
            JenaIOBasedQueriedDataset qdsWrapper = new
JenaIOBasedQueriedDataset( qds );
            ldcache = new SWClLibBasedLinkedDataCache( qdsWrapper );
            Dataset dsARQ = new LinkedDataCacheWrappingDataset( ldcache );

            qe = QueryExecutionFactory.create(queryString, dsARQ);
            ResultSet results = qe.execSelect();

            // Output query results.
            System.out.println("found " + results.getRowNumber() + " of
matching triples!");
            ResultSetFormatter.out(System.out, results);
        }
        catch(Exception e) {
            System.out.println(e.getMessage());
        }
        finally {
            try {
                ldcache.shutdownNow( 4000 );
            } catch (ExecutionException e) {
                e.printStackTrace();
            } catch (TimeoutException e) {
                e.printStackTrace();
            }
        }

        System.out.println("\nall done.");
    }
}

Thank you for the help!!

liyang

On Wed, May 4, 2011 at 5:28 AM, Olaf Hartig
<ha...@in...>wrote:

> Hey liyang,
>
> First, I found and fixed a small bug (which had nothing to do with the
> problem
> you reported). I released a new version of SQUIN: 0.1.1
>
> On 2011-05-04 00:25 l Yu <wyriwyg@gm...> wrote:
> > just a thought: which Jena version we should be using together with the
> > squin-0.1.0.jar file? could it be the version of Jean (ARQ) is not
> correct?
> >
> > On Tue, May 3, 2011 at 8:20 PM, l Yu <wyriwyg@...> wrote:
> >>
> >> Hi,
> [...]
> >> The red line throws an exception like this:
> >>
> >> Exception in thread "main" java.lang.VerifyError: class
> >> org.squin.engine.LinkedDataCacheWrappingDatasetGraph overrides final
> method
> >> getDefaultGraph.()Lcom/hp/hpl/jena/graph/Graph;
> [...]
>
> I tested the code you posted with SQUIN 0.1.1 on my system and it works;
> i.e. I did not get the exception that you got.
>
> I assume -as you suggest- that the problem is caused by using an old
> Jena/ARQ.
> As it says in the README.txt, SQUIN 0.1.1 must be used with the libraries
> from
> the current CVS checkout of the NG4J project. Hence, you must not only
> compile
> your application (or SQUIN itself) with these libraries but you must also
> use
> these libraries to run your application. The versions of Jena and ARQ that
> you
> find in the CVS of NG4J are 2.6.4 and 2.8.8, respectively.
>
> Sorry for the inconvenience of requiring the NG4J CVS. I will try to get
> rid
> of that dependency as soon as possible.
>
> BTW, as an alternative you may download the SQUIN Standalone package
> which contains all necessary libraries in the ./lib/ext/ directory. Hence,
> you
> may use the content of that directory for your CLASSPATH.
>
> Greetings,
> Olaf
>
>
> ------------------------------------------------------------------------------
> WhatsUp Gold - Download Free Network Management Software
> The most intuitive, comprehensive, and cost-effective network
> management toolset available today.  Delivers lowest initial
> acquisition cost and overall TCO of any competing solution.
> http://p.sf.net/sfu/whatsupgold-sd
> _______________________________________________
> Squin-users mailing list
> Squ...@li...
> https://lists.sourceforge.net/lists/listinfo/squin-users
>

Re: [Squin-users] exception happens on this line: Dataset dsARQ = new LinkedDataCacheWrappingDataset( ldcache );

[Olaf H. <ha...@in...>]

Hey liyang,

First, I found and fixed a small bug (which had nothing to do with the problem 
you reported). I released a new version of SQUIN: 0.1.1

On 2011-05-04 00:25 l Yu <wyriwyg@gm...> wrote:
> just a thought: which Jena version we should be using together with the
> squin-0.1.0.jar file? could it be the version of Jean (ARQ) is not correct?
>
> On Tue, May 3, 2011 at 8:20 PM, l Yu <wyriwyg@...> wrote:
>>
>> Hi,
[...]
>> The red line throws an exception like this:
>>
>> Exception in thread "main" java.lang.VerifyError: class
>> org.squin.engine.LinkedDataCacheWrappingDatasetGraph overrides final method
>> getDefaultGraph.()Lcom/hp/hpl/jena/graph/Graph;
[...]

I tested the code you posted with SQUIN 0.1.1 on my system and it works;
i.e. I did not get the exception that you got.

I assume -as you suggest- that the problem is caused by using an old Jena/ARQ. 
As it says in the README.txt, SQUIN 0.1.1 must be used with the libraries from 
the current CVS checkout of the NG4J project. Hence, you must not only compile 
your application (or SQUIN itself) with these libraries but you must also use 
these libraries to run your application. The versions of Jena and ARQ that you 
find in the CVS of NG4J are 2.6.4 and 2.8.8, respectively.

Sorry for the inconvenience of requiring the NG4J CVS. I will try to get rid 
of that dependency as soon as possible.

BTW, as an alternative you may download the SQUIN Standalone package
which contains all necessary libraries in the ./lib/ext/ directory. Hence, you 
may use the content of that directory for your CLASSPATH.

Greetings,
Olaf

Re: [Squin-users] result stream?

[Olaf H. <ha...@in...>]

Hey Martin,

The (late) answer to your other question:

On 2011-03-20 21:25 Martin <m.r@fu...> wrote:
> Hej,
>
> one more question:
>
> The processing of queries can take quite long and the user might not 
> need all results. Is there a way to display results immediately, i.e. 
> while the query is still running?

The new SQUIN version that I recently released comes with a new command line 
interface (see ./bin/squin.sh ) that can be used to execute SPARQL queries 
using the SQUIN query system on the command line. This program does exactly 
what you propose; it prints the query results to stdout in a streaming manner
- at least, when the output format for the result set is plain text.  You may 
disable this behavior using the option  --disable-streaming-output

However, you probably meant adding such a functionality to the SQUIN service. 
I think, enabling streaming results for the SQUIN service is a bit more tricky 
because it would require additional communication between the client and
the SQUIN service than just adhering to the SPARQL protocol. To get this 
"right" it might even be necessary to develop or to use some kind of 
publish/subscribe protocol. I would love to have something like this in SQUIN 
but, to be honest, I don't have the time to develop and implement it (I'm 
currently focussing on the query system in SQUIN).

Greetings,
Olaf

> Thanks.
> Regards,
> Martin

Re: [Squin-users] URI requirements

[Olaf H. <ha...@in...>]

Hey Martin,

First, sorry for the very late reply. It appeared that I was not subscribed to 
the squin-users mailing list :-(
I hope it's still not too late to answer your question.

On 2011-03-20 18:13 Martin <m.r@fu...> wrote:
> Hi SQUIN list,
>
> I am new to the field

Welcome.

> an I didn't have the time to read all the way 
> through the papers - maybe you could help me out:
>
> I understand that SQUIN retrieves information not by consulting triple 
> stores but by dereferencing URIs.

Right.

> So it requires URIs in the query to be 
> valid pointers to RDF data, which is not necessarily the case - is that 
> correct?

Exactly.

> How does the service react to URIs that can't be dereferenced?

It creates an entry in the log file and ignores them.

> Is it possible to have SQUIN use explicitly specified SPARQL endpoints 
> in those cases?

No, at least not at the moment. The query system in SQUIN implements the
link traversal based query execution approach. One of my long-term goals is to 
combine link traversal based query execution with a query federation approach 
that distributes the execution of sub-queries to remote SPARQL endpoints. 
However, I won't have the time to develop this idea in the near future. If you 
are looking for a PhD topic, here's an opportunity ;-)

> Thanks for answers!

Again, sorry for replying way too late.

Cheers,
Olaf

> Take care,
> Martin

Re: [Squin-users] Squin help

[Olaf H. <ha...@in...>]

Hey Ioannis,

First, sorry for the very late reply. It appeared that I was not subscribed to 
the squin-users mailing list :-(
I hope it's still not too late to answer your question.

At 2011-02-16 20:27 Ioannis Parapontis <parapontisj@gm...> wrote:
> Hi there,
>
> I am trying to set up a squin service using the standalone install package.
>
> Sorry to bother you with this but I would like some help in launching the
> service cause i thing i am missing something
>
> In particular with the following points
>
> 1. Move this new SQUIN directory somewhere on your webserver, for example to
> code>/opt/squin</code>.
>
> 2. enter the SQUIN directory, and call java -DOPTIONS=default,plus -jar
> start.jar.

It seems you are trying to get SQUIN running on a Windows machine. Is
that right?

Unfortunately, I cannot provide support for SQUIN on Windows. Sorry! I don't 
have a Windows machine at hand. The corresponding wiki entry that you cite 
here was reported to work by another user. I just copied it into the wiki.

However, if you want to set up a SQUIN service, I suggest that you use a Unix 
system (e.g. any Linux distribution should work).

Greetings,
Olaf

> Thanks
>
> Ioannis

Re: [Squin-users] exception happens on this line: Dataset dsARQ = new LinkedDataCacheWrappingDataset( ldcache );

[l Yu <wy...@gm...>]

just a thought: which Jena version we should be using together with the
squin-0.1.0.jar file? could it be the version of Jean (ARQ) is not correct?

On Tue, May 3, 2011 at 8:20 PM, l Yu <wy...@gm...> wrote:

> Hi,
>
> We really liked the work in SQUIN, and we did give it a first try, as shown
> in this simple code:
>
> import java.util.concurrent.ExecutionException;
> import java.util.concurrent.TimeoutException;
>
> import org.squin.dataset.QueriedDataset;
> import org.squin.dataset.hashimpl.combined.QueriedDatasetImpl;
> import org.squin.dataset.jenacommon.JenaIOBasedQueriedDataset;
> import org.squin.engine.LinkTraversalBasedQueryEngine;
> import org.squin.engine.LinkedDataCacheWrappingDataset;
> import org.squin.ldcache.jenaimpl.JenaIOBasedLinkedDataCache;
> import org.squin.ldcache.ng4jimpl.SWClLibBasedLinkedDataCache;
>
> import com.hp.hpl.jena.query.Dataset;
> import com.hp.hpl.jena.query.QueryExecution;
> import com.hp.hpl.jena.query.QueryExecutionFactory;
> import com.hp.hpl.jena.query.ResultSet;
> import com.hp.hpl.jena.query.ResultSetFormatter;
>
> public class AutomaticLinkTraversalExample {
>
>     public static void main(String[] args) {
>
>         // Specify the query.
>         String queryString =
>         "PREFIX foaf: <http://xmlns.com/foaf/0.1/> " +
>         "SELECT DISTINCT ?i WHERE {" +
>         "<http://www.w3.org/People/Berners-Lee/card#i> foaf:knows ?p . " +
>
>         "?p foaf:interest ?i ." +
>         "}";
>
>         QueryExecution qe = null;
>         JenaIOBasedLinkedDataCache ldcache = null;
>         try {
>
>             LinkTraversalBasedQueryEngine.register();
>
>             // create a Linked Data cache:
>             QueriedDataset qds = new QueriedDatasetImpl();
>             JenaIOBasedQueriedDataset qdsWrapper = new
> JenaIOBasedQueriedDataset( qds );
>             ldcache = new SWClLibBasedLinkedDataCache( qdsWrapper );
>             *Dataset dsARQ = new LinkedDataCacheWrappingDataset( ldcache
> );** // trouble here!!!
> *
>             qe = QueryExecutionFactory.create(queryString, dsARQ);
>             ResultSet results = qe.execSelect();
>
>             // Output query results.
>             ResultSetFormatter.out(System.out, results);
>         }
>         catch(Exception e) {
>             System.out.println(e.getMessage());
>         }
>         finally {
>             try {
>                 ldcache.shutdownNow( 4000 );
>             } catch (ExecutionException e) {
>                 e.printStackTrace();
>             } catch (TimeoutException e) {
>                 e.printStackTrace();
>             }
>         }
>
>         System.out.println("\nall done.");
>     }
> }
>
> The red line throws an exception like this:
>
> Exception in thread "main" java.lang.VerifyError: class
> org.squin.engine.LinkedDataCacheWrappingDatasetGraph overrides final method
> getDefaultGraph.()Lcom/hp/hpl/jena/graph/Graph;
>     at java.lang.ClassLoader.defineClass1(Native Method)
>     at java.lang.ClassLoader.defineClassCond(Unknown Source)
>     at java.lang.ClassLoader.defineClass(Unknown Source)
>     at java.security.SecureClassLoader.defineClass(Unknown Source)
>     at java.net.URLClassLoader.defineClass(Unknown Source)
>     at java.net.URLClassLoader.access$000(Unknown Source)
>     at java.net.URLClassLoader$1.run(Unknown Source)
>     at java.security.AccessController.doPrivileged(Native Method)
>     at java.net.URLClassLoader.findClass(Unknown Source)
>     at java.lang.ClassLoader.loadClass(Unknown Source)
>     at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
>     at java.lang.ClassLoader.loadClass(Unknown Source)
>     at
> org.squin.engine.LinkedDataCacheWrappingDataset.<init>(LinkedDataCacheWrappingDataset.java:25)
>     at
> AutomaticLinkTraversalExample.main(AutomaticLinkTraversalExample.java:40)
>
> Could you please help us on this one?
>
> Thanks!
> liyang
>

[Squin-users] exception happens on this line: Dataset dsARQ = new LinkedDataCacheWrappingDataset( ldcache );

[l Yu <wy...@gm...>]

Hi,

We really liked the work in SQUIN, and we did give it a first try, as shown
in this simple code:

import java.util.concurrent.ExecutionException;
import java.util.concurrent.TimeoutException;

import org.squin.dataset.QueriedDataset;
import org.squin.dataset.hashimpl.combined.QueriedDatasetImpl;
import org.squin.dataset.jenacommon.JenaIOBasedQueriedDataset;
import org.squin.engine.LinkTraversalBasedQueryEngine;
import org.squin.engine.LinkedDataCacheWrappingDataset;
import org.squin.ldcache.jenaimpl.JenaIOBasedLinkedDataCache;
import org.squin.ldcache.ng4jimpl.SWClLibBasedLinkedDataCache;

import com.hp.hpl.jena.query.Dataset;
import com.hp.hpl.jena.query.QueryExecution;
import com.hp.hpl.jena.query.QueryExecutionFactory;
import com.hp.hpl.jena.query.ResultSet;
import com.hp.hpl.jena.query.ResultSetFormatter;

public class AutomaticLinkTraversalExample {

    public static void main(String[] args) {

        // Specify the query.
        String queryString =
        "PREFIX foaf: <http://xmlns.com/foaf/0.1/> " +
        "SELECT DISTINCT ?i WHERE {" +
        "<http://www.w3.org/People/Berners-Lee/card#i> foaf:knows ?p . " +
        "?p foaf:interest ?i ." +
        "}";

        QueryExecution qe = null;
        JenaIOBasedLinkedDataCache ldcache = null;
        try {

            LinkTraversalBasedQueryEngine.register();

            // create a Linked Data cache:
            QueriedDataset qds = new QueriedDatasetImpl();
            JenaIOBasedQueriedDataset qdsWrapper = new
JenaIOBasedQueriedDataset( qds );
            ldcache = new SWClLibBasedLinkedDataCache( qdsWrapper );
            *Dataset dsARQ = new LinkedDataCacheWrappingDataset( ldcache );*
* // trouble here!!!
*
            qe = QueryExecutionFactory.create(queryString, dsARQ);
            ResultSet results = qe.execSelect();

            // Output query results.
            ResultSetFormatter.out(System.out, results);
        }
        catch(Exception e) {
            System.out.println(e.getMessage());
        }
        finally {
            try {
                ldcache.shutdownNow( 4000 );
            } catch (ExecutionException e) {
                e.printStackTrace();
            } catch (TimeoutException e) {
                e.printStackTrace();
            }
        }

        System.out.println("\nall done.");
    }
}

The red line throws an exception like this:

Exception in thread "main" java.lang.VerifyError: class
org.squin.engine.LinkedDataCacheWrappingDatasetGraph overrides final method
getDefaultGraph.()Lcom/hp/hpl/jena/graph/Graph;
    at java.lang.ClassLoader.defineClass1(Native Method)
    at java.lang.ClassLoader.defineClassCond(Unknown Source)
    at java.lang.ClassLoader.defineClass(Unknown Source)
    at java.security.SecureClassLoader.defineClass(Unknown Source)
    at java.net.URLClassLoader.defineClass(Unknown Source)
    at java.net.URLClassLoader.access$000(Unknown Source)
    at java.net.URLClassLoader$1.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at java.net.URLClassLoader.findClass(Unknown Source)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    at sun.misc.Launcher$AppClassLoader.loadClass(Unknown Source)
    at java.lang.ClassLoader.loadClass(Unknown Source)
    at
org.squin.engine.LinkedDataCacheWrappingDataset.<init>(LinkedDataCacheWrappingDataset.java:25)
    at
AutomaticLinkTraversalExample.main(AutomaticLinkTraversalExample.java:40)

Could you please help us on this one?

Thanks!
liyang

[Squin-users] result stream?

[Martin <m....@fu...>]

Hej,

one more question:

The processing of queries can take quite long and the user might not 
need all results. Is there a way to display results immediately, i.e. 
while the query is still running?

Thanks.
Regards,
Martin

[Squin-users] URI requirements

[Martin <m....@fu...>]

Hi SQUIN list,

I am new to the field an I didn't have the time to read all the way 
through the papers - maybe you could help me out:

I understand that SQUIN retrieves information not by consulting triple 
stores but by dereferencing URIs. So it requires URIs in the query to be 
valid pointers to RDF data, which is not necessarily the case - is that 
correct?

How does the service react to URIs that can't be dereferenced?

Is it possible to have SQUIN use explicitly specified SPARQL endpoints 
in those cases?

Thanks for answers!

Take care,
Martin

[Squin-users] Squin help

[Ioannis P. <par...@gm...>]

Hi there,

I am trying to set up a squin service using the standalone install package.

Sorry to bother you with this but I would like some help in launching the
service cause i thing i am missing something

In particular with the following points

1. Move this new SQUIN directory somewhere on your webserver, for example to
code>/opt/squin</code>.

2. enter the SQUIN directory, and call java -DOPTIONS=default,plus -jar
start.jar.

Thanks

Ioannis