Accessing rdf:Bag information

[tedca77]

Last month, I posted a question of how to access specific rdf:Bag sections for an RDF within the XMP section of JPEG images (XMP is RDF/XML). I did not get a reply but have eventually figured it out myself. Section 6 "Working with rdf](rdf:Alt, rdf:Bag, rdf:Seq)" does not really provide much help for this type of issue. It works, but I am still not 100% sure this is the best way to do it. Looking at other messages, not many people are using RDF4J in this way.

I have put a few examples together for adding a rdf:Bag structure to a model and then updating the model. If helpful, I would be happy to make them more generic and contribute to the documentation in this area.

I wanted to update the following structure:

<Iptc4xmpExt:LocationCreated>   
   <rdf:Bag> 
	<rdf:li Iptc4xmpExt:City="LC1-City"      
	Iptc4xmpExt:CountryCode="LC1"      
	Iptc4xmpExt:CountryName="LC1-Country Name"  
	Iptc4xmpExt:ProvinceState="LC1-State or Province"     
	Iptc4xmpExt:Sublocation="LC1-Sublocation"  
	Iptc4xmpExt:WorldRegion="LC1-World Region"/>    
  </rdf:Bag>     
</Iptc4xmpExt:LocationCreated>

Once read in by RDF4J - it is represented like this in XML :

<rdf:Description rdf:about="http://example.org/Image">
	<Iptc4xmpExt:LocationCreated rdf:nodeID="b6538c1ef06545b68aa38c4f65ce305c52"/>
</rdf:Description>

<rdf:Description rdf:nodeID="b6538c1ef06545b68aa38c4f65ce305c52">
	<rdf:type rdf:resource="http://www.w3.org/1999/02/22-rdf-syntax-ns#Bag"/>
	<rdf:_1 rdf:nodeID="b6538c1ef06545b68aa38c4f65ce305c53"/>
</rdf:Description>

<rdf:Description rdf:nodeID="b6538c1ef06545b68aa38c4f65ce305c53">
	<Iptc4xmpExt:City>LC1-City</Iptc4xmpExt:City>
	<Iptc4xmpExt:CountryCode>LC1</Iptc4xmpExt:CountryCode>
	<Iptc4xmpExt:CountryName>LC1-Country Name</Iptc4xmpExt:CountryName>
	<Iptc4xmpExt:ProvinceState>LC1-State or Province</Iptc4xmpExt:ProvinceState>
	<Iptc4xmpExt:Sublocation>LC1-Sublocation</Iptc4xmpExt:Sublocation>
	<Iptc4xmpExt:WorldRegion>LC1-World Region</Iptc4xmpExt:WorldRegion>
</rdf:Description>

Here is the code to add the structure, (if it does not already exist) using ModelBuilder:

  BNode locationNode = bnode();
           BNode bagNode = bnode();
           ModelBuilder builder = new ModelBuilder();
           builder
                   .setNamespace("rdf",RDF.NAMESPACE)
                   .setNamespace(IPTC_E_PREFIX,IPTC_E_NAMESPACE)
                   .setNamespace(IPTC_C_PREFIX,IPTC_C_NAMESPACE)
                   .defaultGraph()
                   .subject(IRI_RESOURCE)
                   .add(IRI_LOCATIONCREATED, locationNode)
                   .subject(IRI_LOCATIONCREATED)
                   .subject(locationNode)
                   .add(RDF.TYPE,RDF.BAG)
                  .add(BAG_1,bagNode);
           builder.namedGraph(BAG_1)
                    .subject(bagNode)
                   .add(IRI_E_COUNTRY,"")
                   .add(IRI_E_COUNTRYCODE,"")
                   .add(IRI_E_STATE,"")
                   .add(IRI_E_SUBLOCATION,"")
                   .add(IRI_E_CITY,"")
                   .add(IRI_E_WORLDREGION,"");
           Model mm = builder.build();
           //add to the model
           m.addAll(mm);
           //add namespaces
           mm.getNamespaces().stream()
                   .filter(ns -> !m.getNamespace(ns.getPrefix()).isPresent())
                   .forEach(m::setNamespace);
           Rio.write(m, System.out, RDFFormat.RDFXML);

To retrieve a value is relatively simple in my case, as there is only ever one LI item in the list (according to XMP specification.) , so we can just filter on the Predicate 👍

Model iriFilter=model.filter(null,IRI_E_COUNTRY,null);

To update the structure, however, we have to find the correct locationNode and Bag node:

Model locationFilter = m.filter(IRI_RESOURCE, IRI_LOCATIONCREATED, null);
          Resource locationNode = objectResource(locationFilter).orElse(null);
          ValueFactory vf = SimpleValueFactory.getInstance();
          if(locationNode != null) {
              Model bagFilter = m.filter(locationNode,null, null);
              // there may be multiple values - only one is supported by IPTC/XMP
              int count =0;
              for(Statement bags : bagFilter)
              {
                   if(!bags.getObject().equals(RDF.BAG))
                  {
                      Resource bagNode=(Resource) bags.getObject();
                      Model valueFilter = m.filter(bagNode,IRI_E_CITY, null);
                     // code to replace based on the filter :  
                  }
              }
         }

Hope this is useful !