This section contains information about performing day to day administration tasks with an OWLIM-SE repository. Most of these standard operations can be achieved using the Sesame software. Some information is repeated here and tailored to the specifics of OWLIM-SE.
In order to preserve the context across export/import a context-aware RDF file format must be used, e.g. TriG. After serialising the repository to a file with this format (this can be done through the Sesame workbench Web application) the file can be imported with the following steps:
The TriX format (an XML-based context-aware RDF serialisation) can also be used.
In general RDF data can be loaded into a given Sesame repository using the 'load' command in the Sesame console application or directly through the workbench web application. However, neither of these approaches will work when using a very large number of triples, e.g. a billion statements. A common solution would be to convert the RDF data into a line-based RDF format (e.g. N-triples) and then split it into many smaller files (e.g. using the linux command 'split'). This would allow each file to be uploaded separately using either the console or workbench applications.
The Sesame openRDF workbench Web application has an export function that can be used to export the contents of moderately sized repositories. However, using this with large repositories (more than a hundred million statements or more) causes problems, usually timeouts for the Servlet container (Tomcat) hosting the application. Also, the workbench cannot be used when using OWLIM-SE without Tomcat.
The basic procedure is to export the RDF data from the old version of OWLIM-SE and then reload it in to a new repository instance that uses the new version of OWLIM-SE. Exporting is straightforward when using the Sesame workbench – simply click the 'Export' button, choose the format and click 'download'. To import in to a new repository, click 'add', select a format, specify the file and base URI, then click 'Upload'.
Once created, the repository configuration is maintained in the Sesame SYSTEM repository. There is no easy generic way of changing this configuration, but there are several possibilities.
A OWLIM-SE repository image can become corrupted if OWLIM-SE (or the Java application that hosts it) crashes. In particular, the repository gets corrupted if OWLIM-SE is interrupted after a successful commit but before flushing the update to disk.
java -cp lib/*:ext/* com.ontotext.trree.DatabaseRestorer STORAGE_FOLDER_PATH ENTITY_INDEX_SIZE RULE_SET
The following three parameters are required:
To ensure that all committed statements are written to disk storage, a transaction can be committed containing a statement with the special predicate <http://www.ontotext.com/owlim/system#flush>, e.g.
This statement can be committed with other statements as a single transaction or separately in its own transaction. All repository data is flushed to disk after the transaction is committed.
If the Lucene jar file is not on the classpath then the following exception will be thrown:
Changing the rule-set can be achieved in the same way as changing any other configuration parameter, except that it is necessary to re-compute the inferred statements with the new rule-set. This does not happen automatically, but can be forced by committing a transaction containing a statement with the special re-infer predicate (the subject and object can be anything), e.g.
There is no facility at present to back up a repository while it is running. Therefore, to backup a repository it must be shutdown gracefully and a copy of its storage directory (and any sub-directories) taken.
Ontologies and schemas imported at initialisation time using the 'imports' configuration parameter are flagged as read-only. This is the preferred method for using ontologies/schemas as it allows the incremental delete algorithm to be very efficient. However, there are times when it is necessary to change a schema and this can be done inside a 'system transaction'.
This statement is not inserted in to the database, rather it serves as a flag that tells OWLIM that it can ignore the read-only flag for imported statements.
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