This chapter briefly explains the purpose and the scope of this document, its place in the OWLIM user documentation set, and provides some suggestions for efficient use. It starts with an introduction on the differences between the two editions of OWLIM, which facilitates the understanding of the OWLIM product family, the design objectives behind each of the versions and the rationale behind the structuring of the documentation.
OWLIM-Lite and OWLIM-SE are identical in terms of usage and integration. Apart from a few differences in configuration parameters, these editions have the same functionality and implement the same Sesame APIs. However, they use different indexing, inference and query evaluation implementations, which results in different performance, memory requirements, and scalability.
OWLIM-Lite is designed for medium data volumes (below 100 million statements) and for prototyping. Its key characteristics are as follows:
- reasoning and query evaluation are performed in main memory;
- it employs a persistence strategy that ensures data preservation and consistency;
- the loading of data, including reasoning, is extremely fast;
- easy configuration.
OWLIM-SE is suitable for handling massive volumes of data and very intensive querying activities. It is designed as an enterprise-grade database management system. This has been made possible through:
- file-based indices, which enable it to scale to billions of statements even on desktop machines;
- special-purpose index and query optimization techniques, ensuring fast query evaluation against very large volumes of data;
- optimized handling of owl:sameAs (identifier equality) to boost efficiency for data integration tasks;
- efficient retraction of explicit statements and their inferences, which allows for efficient delete operations.
OWLIM-Enterprise is a component that can manage and synchronise multiple OWLIM instances in a resilient and scalable cluster configuration.
Further discussion on the differences between OWLIM's editions can be found in the OWLIM Primer. There is also a [roadmap] that shows the development plans for each of these editions.
This document is designed for software engineers, system integrators and system administrators who wish to integrate the OWLIM-Lite semantic repository in to their applications or who wish to use OWLIM-Lite and Sesame as a stand-alone server for storing and processing structured data. It is also useful for system administrators who need to support and maintain a OWLIM-Lite repository.
The reader is assumed to be familiar with databases, but not an expert in semantic database systems, semantic information retrieval, Semantic Web, or OWLIM itself. Less experienced readers are recommended to read the OWLIM Primer where the required minimum of Semantic Web and related concepts is covered, as well as OWLIM basics.
This document has multiple uses:
- To provide the information necessary to use OWLIM-Lite repositories via the Sesame APIs;
- To give instructions on managing repositories through the Sesame web front-end;
- For familiarisation with OWLIM-Lite's reasoning capabilities and rule language;
- To enable the creation of custom installations and configurations of OWLIM-Lite;
- To introduce the most important factors that affect the efficiency of OWLIM-Lite and to provide some productivity tips.
Readers new to OWLIM should read the OWLIM Primer first and then this document in its entirety. This will guarantee that the necessary basic information has been covered in sufficient depth. After some experience using OWLIM, this guide can be used as a reference for carrying out specific tasks.
The following conventions are used in this document:
- Code examples are listed in a typewriter-like font
- Other important terms, when first introduced, will be written in italics
- Formulas are always in italics
- References are given in square brackets, e.g.  means "Refer to publication #3 in the References section"
- OWLIM-Lite, OWLIM-SE and OWLIM-Enterprise are referred to collectively as "OWLIM" in those cases where it is not necessary to distinguish between the editions, i.e. the specifications, features, and/or settings described are common for all editions