FAQ¶

Where does the name “OWLIM” (the former GraphDB name) come from?

The name originally came from the term “OWL In Memory” and was fitting for what later became OWLIM-Lite. However, OWLIM-SE used a transactional, index-based file-storage layer where “In Memory” was no longer appropriate. Nevertheless, the name stuck and it was rarely asked where it came from.

What kind of SPARQL compliance is supported?

All GraphDB editions support:

• SPARQL 1.1 Protocol for RDF
• SPARQL 1.1 Query
• SPARQL 1.1 Update
• SPARQL 1.1 Federation
• SPARQL 1.1 Graph Store HTTP Protocol

See also SPARQL compliance.

How is GraphDB related to RDF4J?

GraphDB is a semantic repository, packaged as a Storage and Inference Layer (Sail) for the RDF4J framework and it makes extensive use of the features and infrastructure of RDF4J, especially the RDF model, RDF parsers and query engines.

For more details, see the GraphDB RDF4J.

What are the advantages of using solid-state drives as opposed to hard-disk drives?

We recommend using enterprise grade SSDs whenever possible as they provide a significantly faster database performance compared to hard-disk drives.

Unlike relational databases, a semantic database needs to compute the inferred closure for inserted and deleted statements. This involves making highly unpredictable joins using statements anywhere in its indices. Despite utilising paging structures as best as possible, a large number of disk seeks can be expected and SSDs perform far better than HDDs in such a task.

How to find out the exact version number of GraphDB?

The major/minor version and build number are part of the GraphDB distribution .zip file name. The embedded owlim .jar file has the major and minor version numbers appended.

In addition, at start up, GraphDB logs the full version number in an INFO logger message, e.g., [INFO ] 2016-04-13 10:53:35,056 [http-nio-7200-exec-8 | c.o.t.f.GraphDBFreeSchemaRepository] Version: 7.0, revision: -2065913377.

The following DESCRIBE query:

DESCRIBE <http://www.ontotext.com/SYSINFO> FROM <http://www.ontotext.com/SYSINFO>

returns pseudo-triples providing information on various GraphDB states, including the number of triples (total and explicit), storage space (used and free), commits (total and if one is in progress), the repository signature, and the build number of the software.

How to retrieve repository configurations?

To see what configuration data is stored in a GraphDB repository, go to Repositories and use Download repository configuration as Turtle icon

Then you could open the result file named repositoryname-config.ttl

Why can’t I use my custom rule file (.pie) - an exception occurred?

To use custom rule files, GraphDB must be running in a JVM that has access to the Java compiler. The easiest way to do this is to use the Java runtime from a Java Development Kit (JDK).