Hi,
I'm attaching two simple JAVA classes which I'm using for testing (there
are some comments there describing what results I got). The JAVA app and
Fuseki are on the same server. The FusekiTest3 is invoking
DatasetAccessorFactory.createHTTP() (so I think this is what you mean by
"remote" implementation) and FusekiTest2 is using
RDFConnection.fetchDataset (which is the slowest operation).
The GRAPH clause gives me expected results (returns the newly added
triple), but why FROM should be wrong? We use FROM clause in many of our
queries and we didn't notice anything wrong/unexpected when using TDB
dataset. With Fuseki FROM seems to return the content of the default graph
and not the graph indicated by the FROM <named-graph-IRI>.
Both tests fail to preserve the newly added triple.
Here are the maven artifacts I'm using for the client app (maybe I should
download some Fuseki specific JAR?):
<dependency>
<groupId>org.apache.jena</groupId>
<artifactId>jena-tdb</artifactId>
<version>3.5.0</version>
<type>jar</type>
</dependency>
<dependency>
<groupId>org.apache.jena</groupId>
<artifactId>apache-jena</artifactId>
<version>3.5.0</version>
<type>zip</type>
</dependency>
<dependency>
<groupId>org.apache.jena</groupId>
<artifactId>jena-csv</artifactId>
<version>3.5.0</version>
<type>jar</type>
</dependency>
Thanks,
Piotr
2017-12-20 16:52 GMT-05:00 Andy Seaborne <[email protected]>:
>
>
> On 20/12/17 18:28, Piotr Nowara wrote:
>
>> Hi,
>>
>> thanks for answering so quickly.
>>
>> I tried two different solutions:
>>
>> 1) Merging models obtained using DatasetAccessor
>>
>
> Which implementation of DatasetAccessor? (local or remote?)
>
> Model portal = accessor.getModel("http://www.myGraph.com/portal";);
>> Model defaultM = accessor.getModel();
>> Model external = accessor.getModel("http://www.
>> myGraph.com/external
>> ");
>> dataset = DatasetFactory.create(external
>> .add(portal).add(defaultM));
>>
>> 2) RDFConnection - works much slower than the method above (which is not
>> surprise since you said it can affect the performance negatively)
>>
>
> and this is a remote RDFConnection? (otherwise it should perform, with
> default Isolation, the same)
>
>
>> I noticed two confusing issues when working with those datasets:
>> Issue 1: SPARQL SELECT would produce diferent results
>>
>
> in what way different?
>
> depending on where
>> the named graph IRI was defined in the query (FROM clause vd. WHERE
>> clause):
>> SELECT * FROM <http://www.myGraph.com/portal> WHERE {?s ?p ?o}
>> behaves differently than:
>> SELECT * WHERE {GRAPH <http://www.myGraph.com/portal> {?s ?p ?o}}
>>
>
> GRAPH is correct, FROM is wrong.
>
>
>> Issue 2: After ading a triple using INSERT DATA statement the triple was
>> present in the graph but dissapeard after closing the connection despite
>> the fact I did dataset.commit()
>>
>
> Complete example?
>
>
> We didn't experience those issues when working with a "local" Jena TDB. For
>> now we will probably stick to the TDB version, but someday we would need
>> the multi-user functionality Fuseki offers anyway. It seems that we will
>> have to revise all our SPARQL queries to make it Fuseki-ready which means
>> migrating from TDB to Fuseki will be more difficult for us than migrating
>> from another triple-store we were using in the past to Jena TDB that went
>> very smoothly. I'm still wondering whether or not I'm missing something
>> regarding Fuseki.
>>
>> Thanks,
>> Piotr
>>
>>
>> 2017-12-20 5:40 GMT-05:00 Andy Seaborne <[email protected]>:
>>
>>
>>>
>>> On 19/12/17 21:41, Piotr Nowara wrote:
>>>
>>> Hi,
>>>>
>>>> I got a TDB powered JAVA app which is issuing a lot of SPARQL UPDATES
>>>> and
>>>> SELECTS (most of them accessing multiple named graphs at once). My app
>>>> obtains a Jena connection using this simple API call:
>>>>
>>>> this.dataset = TDBFactory.createDataset(this.storagePath);
>>>>
>>>> Then this dataset object is used to run SPARQL UPDATES and SELECTS.
>>>>
>>>> I would like to replicate this solution using Jena Fuseki but I wonder
>>>> if
>>>> that’s possible since the DatasetAccessor class provides only methods to
>>>> access separate named graphs. What I need is a database/dataset level
>>>> access. The Fuseki database should be persistent.
>>>>
>>>> I'd be grateful for any clue or code example.
>>>>
>>>> Query and update work on datasets.
>>>
>>> RDFConnection
>>> http://jena.apache.org/documentation/rdfconnection/
>>> is the combined interface to both local and remote datasets and includes
>>> some operations that include whole GET/POST/PUT of datasets
>>>
>>> RDFConnection.connect("http:/localhost:3030/myDataset")
>>>
>>> for migration from local, note that data is copied across the network
>>> when
>>> doing dataset operations. RDFConnection has whole dataset operations in
>>> the
>>> style of SPARQL Graph Store Protocol (=DatasetAccessor) operations.
>>> If your graphs and dataset are large is maybe not what you want.
>>>
>>> Because this across the network, the semantics of lcoal and remote are
>>> not
>>> identical unless you ask the local mode to do copying:
>>>
>>> RDFConnection.connect(datasets, Isolation.COPY)
>>>
>>> which is a good simulation for a local/remote (and slower for local than
>>> no COPY)
>>>
>>> Andy
>>>
>>>
>>>
>>>> Thanks,
>>>>
>>>> Piotr
>>>>
>>>>
>>>>
>>
