Barry, You create a dataset that is comprised of the following:
defaultGraph -> unionModel namedGraph(https://www.tno.nl/agrifood/graph/pizza/data) namedGraph(https://www.tno.nl/agrifood/graph/pizza/onto) <https://www.tno.nl/agrifood/graph/pizza/onto> https://www.tno.nl/agrifood/graph/pizza/data is loaded from file:src/main/resources/dummy1.ttl https://www.tno.nl/agrifood/graph/pizza/onto is loaded from file:src/main/resources/dummy2.ttl defaultGraph is the union of two graphs defaultGraph.root is loaded from file:src/main/resources/dummy1.ttl defaultGraph.sub1 is loaded from file:src/main/resources/dummy2.ttl writing triples into the dataset will write to the defaultGraph. The defaultGraph being a uniongraph will write to the first graph (default.Graph.root). While they are initialized with the same data (file:src/main/resources/dummy1.ttl), this is not the same as the https://www.tno.nl/agrifood/graph/pizza/data named graph. Your example basically has 4 graphs, 2 in defaultGraph and 2 named graphs. Claude On Fri, Sep 27, 2019 at 3:57 PM Nouwt, B. (Barry) <barry.no...@tno.nl.invalid> wrote: > Hi Claude, thanks for the explanation: from the dataset-as-quads > perspective it does indeed sound logical that empty graphs do not exist. > > Regarding your second answer, I've added some additional information below > (i.e. these can also be found on the github repo: > https://github.com/barrynl/jena-example). The SPARQL is executed on the > dataset described by the conf.ttl below. It does not have a GRAPH specified > in the query and it would indeed go into the default graph, which is a > UnionModel of the two in-memory named graphs. Of which the rootGraph should > store this new data. The details of how I inspect the different graphs can > be found in the Java code in the link above. If you run this example and > inspect the output log and 'dataset' variable (and the inner models and > graphs) with a debugger, the data sometimes shows up and sometimes doesn't. > I am trying to understand why... Any more ideas? > > Regards, Barry > > ---------------------------------------- SPARQL > ---------------------------------------- > INSERT DATA { > :test rdf:type pizza:Pizza . > :test pizza:hasCountryOfOrigin < > http://192.168.99.100/pizza/Italy> . > :test pizza:hasBase <http://192.168.99.100/pizza/23_base> > . > :test pizza:hasSpiciness < > http://192.168.99.100/pizza/23_flauw> . > :test pizza:hasTopping :18-Tomaat . > :test pizza:hasTopping :18-mozzerella . > :test pizza:hasTopping :18-rundergehakt . > } > > ---------------------------------------- conf.ttl > ---------------------------------------- > > @prefix : <#> . > @prefix fuseki: <http://jena.apache.org/fuseki#< > http://jena.apache.org/fuseki>> . > @prefix rdf: <http://www.w3.org/1999/02/22-rdf-syntax-ns#< > http://www.w3.org/1999/02/22-rdf-syntax-ns>> . > @prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#< > http://www.w3.org/2000/01/rdf-schema>> . > @prefix ja: <http://jena.hpl.hp.com/2005/11/Assembler#< > http://jena.hpl.hp.com/2005/11/Assembler>> . > @prefix xsd: <http://www.w3.org/2001/XMLSchema#< > http://www.w3.org/2001/XMLSchema>> . > > :service1 rdf:type fuseki:Service ; > fuseki:name "test" ; > fuseki:serviceQuery "query" ; # SPARQL query service > fuseki:serviceUpdate "update" ; > fuseki:serviceUpload "upload" ; # Non-SPARQL upload service > fuseki:serviceReadWriteGraphStore "data" ; # SPARQL Graph store > protocol (read and write) > # A separate read-only graph store endpoint: > fuseki:serviceReadGraphStore "get" ; # SPARQL Graph store protocol > (read only) > fuseki:dataset :dataset . > > :dataset rdf:type ja:RDFDataset ; > ja:defaultGraph :unionModel ; > ja:namedGraph > [ ja:graphName <https://www.tno.nl/agrifood/graph/pizza/data> > ; > ja:graph :itemGraph ] ; > ja:namedGraph > [ ja:graphName <https://www.tno.nl/agrifood/graph/pizza/onto> > ; > ja:graph :ontoGraph ] > . > > :unionModel rdf:type ja:UnionModel ; > ja:rootModel :itemGraph ; > ja:subModel :ontoGraph . > > :itemGraph rdf:type ja:MemoryModel ; > ja:content [ ja:externalContent > <file:src/main/resources/dummy1.ttl> ] . > > :ontoGraph rdf:type ja:MemoryModel ; > ja:content [ ja:externalContent > <file:src/main/resources/dummy2.ttl> ] . > > > > > -----Original Message----- > From: Claude Warren <cla...@xenei.com> > Sent: donderdag 26 september 2019 12:10 > To: users@jena.apache.org > Subject: Re: [UnionModel] question about unexpected behaviour > > Empty graphs in Fuseki simply don't exist. They no more exist than a > predicate that has not been used. Named graphs only come into existence > when there is at least one triple added to it. If you think about datasets > as collections of quads (<g> <s> <p> <o>) then you can see that the dataset > can only locate graphs that have data. The only other option is that an > infinite number of graphs exist, in which case listing all the graphs would > be impossible. I am sure there is a deep philosophical discussion here but > the Jena rule is that if the graph does not have data it does not exist. > > As for your second question, you did not give an example of how you > inserted the data. If you did not provide a graph name to insert into then > the data would go into the default graph named "urn:x-arq:DefaultGraph" > (defined in org.apache.jena.sparql.core.Quad.defaultGraphIRI). If you did > provide the graph name then the data would be inserted into that graph as > your debugging shows. When you say it does not exist in the graph are you > referring to on disk? How did you write the data back out? The UnionModel > depends on the underlying models to preserve their data. If those models > are in-memory models then they will not be written back to disk, if they > are TDB models (or other similar auto storing models) then they should be > written back to the underlying storage. This assumes that all transactions > and other issues are correctly handled. > > Claude > > > > On Thu, Sep 26, 2019 at 10:05 AM Nouwt, B. (Barry) > <barry.no...@tno.nl.invalid> wrote: > > > Hi all, > > > > I am trying to get the Apache Jena UnionModel working for my scenario, > > but I keep encountering unexpected behavior. I've set up a minimal, > > free-standing example on github in this repository (clone the git > > repo, configure Maven in your IDE and execute the main() method, I.e. > > it probably does not run from the .jar): > > > > https://github.com/barrynl/jena-example > > > > > > > > I have two questions related to this example: > > > > My first question is related to empty graphs in Jena Fuseki. If I load > > the conf.ttl (from the git repo above) at startup in Apache Jena > > Fuseki without the dummy data in the two named graphs, the two graphs > > seem to disappear (I think this does not happen in my Java Example). I > > read somewhere that empty graphs are automatically deleted in Fuseki > > to prevent old graphs from showing up in the Fuseki interface. For my > > use case I would like to configure two (possibly empty at first) named > > graphs via a conf.ttl and be able to store data in them afterwards. Is > this possible? > > > > My second question is about the demonstraded behaviour of the Java > > example in the git repository above. I load a dataset with a > > UnionModel from a conf.ttl file and insert new data in it via SPARQL. > > Although the new data shows up in the select query, it does not show > > up in either of the two names graphs the UnionModel consists of. My > > question is: where is this data stored if not in one of the names > > graphs? (If I inspect the UnionModel via a debugger, the inserted data > > DOES show up in the correct named graph) > > > > Hopefully someone can shed some light on this behaviour. Thanks in > advance! > > > > Regards, Barry > > This message may contain information that is not intended for you. If > > you are not the addressee or if this message was sent to you by > > mistake, you are requested to inform the sender and delete the > > message. TNO accepts no liability for the content of this e-mail, for > > the manner in which you use it and for damage of any kind resulting > > from the risks inherent to the electronic transmission of messages. > > > > > -- > I like: Like Like - The likeliest place on the web < > http://like-like.xenei.com> > LinkedIn: http://www.linkedin.com/in/claudewarren > -- I like: Like Like - The likeliest place on the web <http://like-like.xenei.com> LinkedIn: http://www.linkedin.com/in/claudewarren
