BigOWLIM is a high-performance semantic repository, implemented in Java and packaged as a Storage and Inference Layer (SAIL) for the Sesame RDF database. BigOWLIM uses the TRREE engine to perform RDFS, OWL DLP, and OWL Horst reasoning, based on forward-chaining of entailment rules. The most expressive language supported is a combination of limited OWL Lite and unconstrained RDFS. BigOWLIM can manage billions of explicit statements on server hardware. A principle limitation of BigOWLIM is the relatively slow delete operation. The upload, reasoning, and the query evaluation proceed fast even against huge ontologies and datasets.
In contrast to SwiftOWLIM (the “standard” in-memory version), BigOWLIM uses a version of TRREE (code-named BigTRREE), which performs reasoning and query evaluation directly against the permanent image of the repository. The persistence is implemented through binary files with a proprietary format. BigTRREE includes a query optimization module so that the query evaluation is no longer dependent on the particular triple pattern ordering of the queries. Another important feature of BigOWLIM is the special handling of equality (owl:sameAs statements) that overcomes the inefficiency faced by SwiftOWLIM in case of large "classes" of equivalent resources, interconnected via owl:sameAs.
BigOWLIM has much lower memory requirements, as compared to SwiftOWLIM: LUBM(50,0), including almost 7M statements, can be handled in 11 min on a notebook, giving Java only 192MB of RAM. LUBM(1000,0), which includes over 130M statements, is handled in 11h on the same machine, given 1.6GB of RAM. BigOWLIM can be configured to make use of more RAM, if available; a configuration calculator is provided to support the selection of the best parameters with respect to the size of the repository and the memory constraints.
Documentation: Presentation (chek the final slides); System Documentation.
Mailing lists subscription available on OWLIM Mailing lists.
BigOWLIM is currently in Beta-testing phase. Evaluation copies can be provided in case of serious interest; inquiries should be sent to OWLIM-info-at-ontotext.com. BigOWLIM will be available under an RDBMS-like commercial licence on a per-server-CPU basis; it is neither free nor open-source. For most of the applications the free version of OWLIM (SwiftOWLIM) should provide sufficient scale and excellent performance.
The development of OWLIM is partly supported by SEKT project.
BigOWLIM successfully passed the threshold of 1 billion (10^9) statements of OWL/RDF – it loaded an 8000-university dataset of the LUBM benchmark and answered the evaluation queries correctly. Evaluation setup and statistics: