Access Methods

OWLIM 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. Explicit and inferred statements are stored in highly-optimized data structures. The inferred closure is updated through inference at the end of each transaction that modifies the repository.
OWLIM 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 user interface tools. A typical user application uses OWLIM directly through the Sesame SAIL API. When an OWLIM repository is exposed using the Sesame HTTP Server, users can manage the repository through the Sesame Workbench Web application, or with other tools that can integrate with Sesame, e.g. ontology editors like TopBraid Composer.
Sesame comprises a large collection of libraries, utilities and APIs, but the important components for this section are:

• the Sesame classes and interfaces (API) that provide uniform access to SAIL components from multiple vendors/publishers;
• the Sesame server and workbench Web applications (Java Enterprise Edition servlet components, referred to on the diagram above as "Sesame Web UI").

This section will describe using the Sesame API to create and access OWLIM repositories, both on the local file-system and remotely via the Sesame HTTP server. Furthermore, a brief introduction will be given to the Sesame workbench Web application that provides many repository management functions through a convenient user interface.

Sesame Application Programming Interface (API)

Programmatically, OWLIM can be used via the Sesame Java framework of classes and interfaces. Documentation for these interfaces (including Javadoc) can be found at http://www.openrdf.org. Code snippets in the following sections are taken from (or are variations of) the GettingStarted example program that comes with the OWLIM distribution.

Using the Sesame API to access a local OWLIM repository

With Sesame 2, repository configurations are represented as RDF graphs. A particular repository configuration is described as a resource, possibly a blank node, of type:
http://www.openrdf.org/config/repository#Repository
This resource has an 'id', a label and an implementation, which in turn has a type, SAIL type, etc. The example repository configuration from the getting-started example program looks like this:

@prefix rdfs: <http://www.w3.org/2000/01/rdf-schema#>.
@prefix rep: <http://www.openrdf.org/config/repository#>.
@prefix sr: <http://www.openrdf.org/config/repository/sail#>.
@prefix sail: <http://www.openrdf.org/config/sail#>.
@prefix owlim: <http://www.ontotext.com/trree/owlim#>.

[] a rep:Repository ;
   rep:repositoryID "owlim" ;
   rdfs:label "OWLIM Getting Started" ;
   rep:repositoryImpl [
     rep:repositoryType "openrdf:SailRepository" ;
     sr:sailImpl [
       sail:sailType "swiftowlim:Sail" ;
       owlim:ruleset "owl-horst-optimized" ;
       owlim:noPersist "true" ;
       owlim:storage-folder "storage" ;
       owlim:base-URL "http://example.org/owlim#" ;
       owlim:new-triples-file "new-triples-file.nt" ;
       owlim:entity-index-size "200000" ;
       owlim:jobsize "200" ;
       owlim:repository-type "in-memory-repository" ;
       owlim:imports "./ontology/owl.rdfs " ;
       owlim:defaultNS " http://example.org/owlim#" .
     ]
   ].

The Java code to use the configuration to instantiate a repository and get a connection to it is as follows:

Note that the code to parse this file and find the 'root' node for the configuration can be found in the getting-started program.
The procedure is as follows: instantiate a local repository manager with the data directory to use for the repository storage files (repositories will store their data in their own sub-directory from here), add a repository configuration for the desired repository type to the manager, 'get' the repository and open a connection to it. From then on, most activities will use the connection object to interact with the repository, e.g. executing queries, adding statements, committing transactions, counting statements, etc. See the getting-started application for examples.

Using the Sesame API to access a remote OWLIM repository

The Sesame Server is a Web application that allows interaction with repositories using the HTTP protocol. It runs in a JEE compliant servlet container, e.g. Tomcat, and allows client applications to interact with repositories located on remote machines. All that is required to connect to and use a remote repository instead of a local one is to replace the local repository manager for a remote one. The URL of the Sesame Server must be provided, but no repository configuration is needed if the repository already exists on the server. The following lines can be added to the getting-started example program, although a correct URL must be specified:

• commons-httpclient-3.1.jar
• commons-logging-1.1.1.jar
• commons-codec-1.3.jar

Managing repositories with the Sesame Workbench

The installation section explains how to set up an OWLIM repository that is exposed via the Sesame HTTP Server. In summary, the Sesame Server and Workbench applications are deployed to a Tomcat instance. After this, the workbench can be used to connect to the Sesame server and create a repository instance.
When the Sesame server is running, it will show a welcome message at the following URL:

http://<hostname|ip_address>:8080/openrdf-sesame

The server has a simple user interface that shows status, logging and configuration information.
The workbench application, however, provides most repository management functions and is available from the following URL:

http:// <hostname|ip_address>:8080/openrdf-workbench

The workbench lists repositories and their namespaces, allows for the addition and deletion of statements, and provides a query interface for SPARQL and SeRQL query languages.

SPARQL endpoint

The Sesame HTTP server is a fully fledged SPARQL endpoint - the Sesame HTTP protocol is a super-set of the SPARQL 1.1 protocol - that provides an interface for transmitting SPARQL (federated) queries and updates to a SPARQL processing service and returning the results via HTTP to the entity that requested them.

Any tools or utilities designed to interoperate with the SPARQL protocol will function with OWLIM when deployed using the Sesame HTTP server, i.e. the openrdf-sesame Web application.

Graph Store HTTP Protocol

The SPARQL 1.1 Graph Store HTTP Protocol is fully supported for direct and indirect graph names. The W3C working draft has the most details, although further information can be found in the Sesame user guide.

This protocol supports the management of RDF statements in named graphs in the REST style, by providing the ability to get, delete, add to or overwrite statement in named graphs using the basic HTTP methods.