[Question] Loading modes of ontologies with different behaviors

[charbull]

Hello,

I would to have like your opinion on the following:

1- I am using RomanticWeb to create Entities
2- Serializing the entities in an RDF/XML using DotNetRDF

 IGraph g = new Graph();
IList graphList = store().Graphs.ToList();
foreach (IGraph currentGraph in graphList)  {   g.Merge(currentGraph);   }
 RdfXmlWriter rdfXmlWriter = new RdfXmlWriter();
 rdfXmlWriter.Save(g, fileName);

3- I am taking the RDF/XML file and insert it manually in Stardog.
4- After insertion, I am relying on RomanticWeb to load some entities as following:

 IFloor as1 = context.Load<IFloor>(new Uri(nameSpace + "#11-UNIQ-ID"));
 Console.WriteLine(as1.Hasname);

However, I can't retrieve any IEntity, it seems not existent, (even if I see it well in the ontology DB browser.

It seems to work only when:

1- I configure RomanticWeb to be plugged to Stardog through the App.config.
2- I commit from RomanticWeb (context.Commit()) to Stardog,
3- I can load and manipulate all of my objects.

Off course having a direct commit is not a usual situation.
Any idea on what might be happening? Is it the serialization to RDF?
What is context.commit() doing that is different from the serialization?

I looked at the code EntityContext.cs and TripleStoreAdapter.cs, I am not sure if the commit is executed through SPARQL queries?

public void Commit(IEnumerable<DatasetChange> changes)
        {
            var updateCommands = changes.SelectMany(CreateCommands);
            var commands = new SparqlUpdateCommandSet(updateCommands);

            LogTo.Debug("Executing SPARQL Update:{0}{1}", Environment.NewLine, commands);
            ExecuteCommandSet(commands);
        }

Any ideas how to make it compatible with the load (rdf) files.
I am also having this kind of errors sometimes when I am using LINQ queries:

IQueryable<IFloor> typedQuery = from entity in context.AsQueryable<IFloor>()
                                            select entity;

            foreach (IFloor ent in typedQuery)
            {
                Console.WriteLine("- " + ent.Hasname);
            }
            Console.WriteLine("End of results");
            Console.ReadLine();

RomanticWeb.Entities.CardinalityException occurred
  HResult=0x80131500
  Message=Exception of type 'RomanticWeb.Entities.CardinalityException' was thrown.
  Source=RomanticWeb
  StackTrace:
   at RomanticWeb.Entities.ResultAggregations.SingleOrDefault.Aggregate(IEnumerable`1 objects) in S:\TeamCity\buildAgent\work\b59ad31af090d0d3\RomanticWeb\Entities\ResultAggregations\SingleOrDefault.cs:line 25
   at RomanticWeb.Entities.ResultPostprocessing.SimpleTransformer.FromNodes(IEntityProxy parent, IPropertyMapping property, IEntityContext context, IEnumerable`1 nodes) in S:\TeamCity\buildAgent\work\b59ad31af090d0d3\RomanticWeb\Entities\ResultPostprocessing\SimpleTransformer.cs:line 34
   at RomanticWeb.Entities.EntityProxy.TryGetMember(GetMemberBinder binder, Object& result) in S:\TeamCity\buildAgent\work\b59ad31af090d0d3\RomanticWeb\Entities\EntityProxy.cs:line 118
   at RomanticWeb.Entities.Proxies.DynamicExtensions.InvokeGet(Object target, String propertyName) in S:\TeamCity\buildAgent\work\b59ad31af090d0d3\RomanticWeb\Entities\Proxies\DynamicExtensions.cs:line 82
   at ProxyOf_34347631_Hash.get_Hasname()
   at REMI.Program.Main(String[] args) in \REMI\Program.cs:line 43

Ideally, I would like to take a rdf file generated by RomanticWeb and DotNetRDF and loaded in an ontology DB. Then, query the db with RomanticWeb though the context.Load.

Thank you for your help,
Charbel

[alien-mcl]

From what I can see, you're merging all graphs into a single one, including RomanticWeb's meta-graph.
When querying underlying stores, RW uses meta-graph to determine which graph is related to which entity. Unmentioned entities are ignored, which seems to be a case here.

[charbull]

@alien-mcl thank you for your reply.

I eventually exported the graph in Trig and it worked. Is there any way to export the store in json without messing it up?

 store.SaveToFile("C:\\output.trig", new TriGWriter());

Thank you

[alien-mcl]

There is some kind of implementation of JSON-LD writer (see dotnetrdf/dotnetrdf#41), but I don't know what is the status of this feature.

[charbull]

Yes, good point !
I just checked, the actual nuget version of RomanticWeb is dependent on DotNetRDF version 1.0.3.
The Jsonld of DotNetRDF works well and is available in version 2.0.

What do you think the best plan to update to 2.0?

[alien-mcl]

I did update the version from 1.0.3 to higher in the RomanticWeb 1.0 beta (at my fork), but only for .net core. It's due to SPARQL performance issues encountered with InMemoryTripleStore.
I believe updating to 2.0 shouldn't cause bigger problems, but still it's a major version number, thus there may be some breaking changes.
I'll try to pick it ASAP.

[charbull]

Great ! thank you looking forward to it !