Primer Introduction to GraphDB

compared with
Current by Gergana Petkova
on Sep 18, 2014 12:44.

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GraphDB is based on Ontotexts's Triple Reasoning and Rule Entailment Engine (TRREE) -- a native RDF rule-entailment engine. The supported semantics can be configured through the definition of rule-sets. The most expressive pre-defined rule-set combines unconstrained RDFS and OWL- Lite. Custom rule-sets allow tuning for optimal performance and expressivity. GraphDB supports RDFS (section 3.1.2), OWL DLP (section 3.1.5.1), OWL Horst (section 3.1.5.2), most of OWL Lite (section 3.1.5.4) and OWL2 RL (section 3.1.5.3).
The three editions of GraphDB are GraphDB-Lite, GraphDB-SE (standard edition) and GraphDB-Enterprise (cluster configuration). With GraphDB-Lite, reasoning and query evaluation are performed in-memory, while, at the same time, a reliable persistence strategy assures data preservation, consistency, and integrity. GraphDB-SE is the high-performance 'enterprise' edition that scales to massive quantities of data. Typically, GraphDB-Lite can manage millions of explicit statements on desktop hardware, whereas GraphDB-SE can manage billions of statements and multiple simultaneous user sessions. GraphDB-Enterprise is an enterprise grade cluster management component that uses a collection of GraphDB instances to provide a resilient, high-performance semantic database.
The key differences between the editions of GraphDB are discussed in section 4.5 and in the GraphDB presentation \[28\]. The results form a number of benchmarks, as well as plenty of other performance evaluation and analysis information, are available on the Web site [http://www.ontotext.com/products/ontotext-graphdb/|http://www.ontotext.com/products/ontotext-graphdb/].
h1. GraphDB Interoperability and Architecture

OWLIM GraphDB version 3.X 6 is packaged as a Storage and Inference Layer (SAIL) for Sesame version 2.x and makes extensive use of the features and infrastructure of Sesame, especially the RDF model, RDF parsers and query engines.
Inference is performed by the TRREE engine \[39\], where the explicit and inferred statements are stored in highly-optimised data structures that are kept in-memory for query evaluation and further inference. The inferred closure is updated through inference at the end of each transaction that modifies the repository.

!owlim_usage.png!

*{_}Figure 5 - OWLIM Usage and Relationship to Sesame and ORDI{_}*

GraphDB implements the Sesame SAIL interface so that it can be integrated with the rest of the Sesame framework, e.g. the query engines and the web UI. A user application can be designed to use GraphDB directly through the Sesame SAIL API or via the higher-level functional interfaces. When an a GraphDB repository is exposed using the Sesame HTTP Server, users can manage the repository through the Sesame Workbench Web application, or with other tools integrated with Sesame, e.g. ontology editors like Protégé and TopBraid Composer.
The easiest way for developers to integrate their applications with GraphDB is to use it with the Sesame framework as a set of libraries. The installation and configuration of GraphDB are discussed in the quick start and user guides. More information on the various aspects of the Sesame specifications, its architecture and implementations can be found in section 3.2.

* *rdfs*: supports standard RDFS semantics;
* *owl-horst*: OWL dialect close to OWL Horst; the differences are discussed below;
* *owl-max*: a combination of most of OWL- Lite with RDFS;
* *owl2-rl*: Fully conformant OWL2 RL profile \[44\] except for D-Entailment, i.e. reasoning about data types.

h2. OWL Compliance

Regarding OWL compliance, GraphDB supports several OWL like dialects: OWL Horst \[37\] (*owl-horst*), OWL Max (*owl-max*) that covers most of OWL- Lite and RDFS, OWL2 QL (*owl2-ql*) and OWL2 RL (*owl2-rl*).

With the *owl-max* rule-set GraphDB supports the following semantics:
* full RDFS semantics without constraints or limitations, apart from the entailment related to typed literals (known as D-entailment). For instance, meta-classes (and any arbitrary mixture of class, property, and individual) can be combined with the supported OWL semantics
* most of OWL-Lite
* most of OWL Lite
* all of OWL DLP