Is it possible, to query the ontology alongside a virtual graph? I built a test project (Data tables in PostgreSQL - Ontology and mappings in Protege/w Ontop Plugin), and while querying via the Ontop Sparql Tab works fine, the answers only include triplets from the VKG, but triplets from the ontology do not show up. I tried the same in graphDB with an ontop style repository to no avail.
Thank you in advance!
Attila
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I installed Protégé 5.5 and I am interested in the DL expressivity of my ontology.
In the documentation, it is written that this information should be found in the Ontology Metrics view. However, my view does not contain this particular information.
Do I need to install some additional plugin?
Are you saying you cannot find the view, or that the view shows no information?
If it's the former, in Protege, navigate to Window > Views > Ontology views > Ontology metrics.
If it's the latter, you shouldn't need any additional plugin(s).
If the problem persists you'll need to post the file or some trivial example otherwise there is nothing to test.
Here's what I have (using a Mac):
An ontology was created in Protege (v5), incorporating some classes
from established ontologies.
All classes were given the same Base URI.
HermiT, FacT++, Pellet, and Ontop plugin reasoners were used to test the ontology in Protege, and no errors or messages were returned.
Protege's Ontop plugin (v1.8) was used to map the classes to
postgres RDBS column headers (table_column) and exported the R2RML
mapping file.
The Ontop CLI was used to materialize triples through a
jdbc postgres connection the ontology in turtle format, according to
the R2RML .ttl mappings file.
Here's where my interactions with GraphDB (v8.2) start:
The GraphDB repository was created with an OWL2-RL profile with the 'read only' unchecked.
All ontology and materialized data triples were uploaded to GraphDB through graphdb-import folder in turtle format. All options checked on upload, and the same Base URI was provided.
The Class Hierarchy diagram suggests that the imported triples are properly structured.
The Class Relationship circular network graph shows reasonable
relationships between the largest 10 classes.
The Domain-Range graph shows a number of in-going and out-going connections to nodes/individuals with predicates.
SPARQL queries appear to return expected values.
Here's my problem: When I enter the Visual Graph, I don't see anything. When I search and select a value that should have nodes, all I see is the single node with a message "This node has no visible connections."
What does this mean and where can I start troubleshooting? Or is the Visual Graph buggy?
I've been trying to figure out how to mount a SPARQL endpoint for a couple of days, but as much as I read I can not understand it.
Comment my intention: I have an open data server mounted on CKAN and my goal is to be able to use SPARQL queries on the data. I know I could not do it directly on the datasets themselves, and I would have to define my own OWL and convert the data I want to use from CSV format (which is the format they are currently in) to RDF triple format (to be used as linked data).
The idea was to first test with the metadata of the repositories that can be generated automatically with the extension ckanext-dcat, but is that I really do not find where to start. I've searched for information on how to install a Virtuoso server for the SPARQL, but the information I've found leaves a lot to be desired, not to say that I can find nowhere to explain how I could actually introduce my own OWLs and RDFs into Virtuoso itself.
Someone who can lend me a hand to know how to start? Thank you
I'm a little confused. Maybe this is two or more questions?
1. How to convert tabular data, like CSV, into the RDF semantic format?
This can be done with an R2RML approach. Karma is a great GUI for that purpose. Like you say, a conversion like that can really be improved with an underlying OWL ontology. But it can be done without creating a custom ontology, too.
I have elaborated on this in the answer to another question.
2. Now that I have some RDF formatted data, how can I expose it with a SPARQL endpoint?
Virtuoso is a reasonable choice. There are multiple ways to deploy it and multiple ways to load the data, and therefore LOTs of tutorial on the subject. Here's one good one, from DBpedia.
If you'd like a simpler path to starting an RDF triplestore with a SPARQL endpoint, Stardog and Blazegraph are available as JARs, and RDF4J can easily be deployed within a container like Tomcat.
All provide web-based graphical interfaces for loading data and running queries, in addition to SPARQL REST endpoints. At least Stardog also provides command-line tools for bulk loading.
I have this assignment where I have created an rdfs ontology with artists, their songs, their genres, etc using Protégé and populated it with some data. I am now supposed to connect my ontology and it's data with DBPedia's, so that I can SPARQL for my artists' birthdate. I have successfully imported http://dbpedia.org/ontology/ and http://dbpedia.org/property/ into protégé, but I can't find a way to import the data (http://dbpedia.org/resource/).
Can anyone point me in the right direction?
DBpedia datasets are stored and available for download here (http://wiki.dbpedia.org/Downloads2015-04#h96554-1) but Protégé isn't going to perform well (or at all) when you load a dataset of this size into it.
You may be better downloading various entities by hand such as - http://dbpedia.org/data/Blink-182.ntriples and then loading into Protégé. You can go to any DBPedia page. E.G. http://dbpedia.org/page/Ras_Barker and find download links at the bottom.
I‘m working on a project, which the ontology is very large and can not be separated into multi files. I need to analyse the ontology and show part of on a web page, but I am not sure how to get part of the ontology. I've saved the ontology into a OntModel class,should I use jena API or SPARQL to query part of it? It would be the best if the sub ontology is also can convert to OntModel class. Could you please give me an example please? Please help me，any answer would be appreciated！Thank you！