OWLIM-Lite Configuration

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This section gives an overview of configuring a OWLIM-Lite repository. Also covered are the contents of the OWLIM-Lite distribution and a description of the 'getting-started' application that is included. This sample application serves as an example for integrating OWLIM-Lite in to other systems. For a detailed step-by-step guide for installing and setting-up OWLIM-Lite, see the installation section.

Contents of the Distribution Package

The OWLIM-Lite distribution zip file includes the following folders:

Folder Contents
doc User guides and OWLIM primer
ext All required third party libraries. The Sesame 2 installation can be downloaded separately from http://www.openrdf.org/. The folder also contains a copy of Lehigh University Benchmark library (lubm.jar), JUnit library (junit.jar) necessary for executing inference tests, the simple logging framework for Java jar files and the lucene full text search jar
getting-started An example application that uses OWLIM, with all the necessary auxiliary files and folders, see section 8.2
lib Contains the binary executable version of OWLIM-Lite as a JAR (Java library) file
lubm Scripts and configuration files to run the LUBM [12] benchmarks documented in section 10.
templates Contains a OWLIM-Lite repository template file (.ttl) used by the Sesame 2 framework for creating new repositories.

The distribution contains the following files in the root directory of the zip file:

File Description
*.pie Rule files containing definitions of the built-in rule-sets.
OWLIM-Lite_license.pdf The license under which OWLIM-Lite is published.
setvars.cmd
setvars.sh
Scripts (Windows and Linux) that define several environment variables used by the scripts that run the test cases and getting-started application. It should be edited for each installation, as it determines the Java virtual machine to be started, the path to all the relevant JAR files, including those of OWLIM-Lite and Sesame

Getting-Started Application

The OWLIM-Lite distribution comes with a sample application that can be used as a template for building applications that interact with a OWLIM-Lite repository. The source code of this application performs a sequence of typical operations: initialization of the repository, uploading statements, executing queries and obtaining results, deleting statements, etc. This application template comes with:

  • Source code and compiled class files
  • Sample ontology and data files
  • Sesame repository template file
  • Scripts which invoke the application

An easy way to set up an application to use OWLIM-Lite is to copy the getting-started folder and modify the contents as necessary.
There follows a short description on how the getting started application is organized and what the sample code does. The easiest way of getting a good understanding of it is to read the source code of the GettingStarted class, located in the src folder - the code is extensively commented.
The program accepts the following command line parameters:

Parameter Description Default
context If not specified, statements loaded are given the context of the file URL from which the statements were loaded. If specified (context=URI), then all statements loaded are given this URI for a context. If an empty context is used (context=) then all statements loaded have no context (default graph) <none>
config Specifies the repository description file to use to create a repository. Configuration options specified in this file are explained in section 8.5. ./owlim.ttl
flush Indicates whether repository updates shiuld be flushed to disk after every commit false
preload Specifies the folder or file containing RDF data that is loaded automatically when the program starts. If the parameter value specifies a folder then it is searched recursively for all files that contain RDF data. ./preload
queryfile Specifies the file containing queries that are to be executed. The files can contain queries in any format supported by Sesame. ./queries/sample.sparql
repository The repository ID identifying the repository described in the configuration file specified by the config parameter. owlim
showresults Specifies whether the results from queries will be displayed or not. true
showstats Indicates whether to show initialisation statistics after loading the selected data files false
updates Specifies whether the statement insertion and deletion step is performed. false
url Indicates whether to connect to the given remote repository URL - overrides config and repository parameters <none>

To run the program, use the example.cmd / example.sh script. This script requires that the JAVA_HOME environment variable has been set. Alternatively, it can be set directly by editing the setvars.cmd / setvars.sh script in the root folder of the OWLIM-Lite software distribution. If the program is modified to use a custom rule set, then JAVA_HOME must point to the Java Runtime Environment (JRE) of a Java Development Kit (JDK) version 1.6 or later. This is so that the new mechanism for locating the Java compiler can be used.
With the example set up, OWLIM-Lite loads two ontologies at start up as specified by the imports parameter in the repository configuration file, i.e. owlim.ttl. These ontologies are ./ontology/owl.rdfs and ./ontology/example.rdfs. The sample program then loads any other ontologies that it finds in the preload folder. When start up is complete, the program outputs some statistics and lists the namespaces found.
The next step is to load the specified query file and to execute the queries that they contain. Some example query files are included in the queries folder. The files can contain several queries where each query starts with an identifier, enclosed in square brackets ^[ and ] on a single line; everything between two subsequent query identifiers is treated as a SeRQL or SPARQL query and is evaluated against the contents of the prepared repository. You may use also the # sign as a single line comment, so each line starting with # will be ignored. Syntax overview:

#some comment
^[queryid1]
<query line1>
<query line2>
...
<query lineN>
#some other comment
^[nextqueryid]
<query line1>
...
<EOF>

The queries are always evaluated, but the results are output only if the showresults parameter is set to true.
Furthermore, the sample application updates the contents of the repository by inserting a statement using RepositoryConnection.addStatement() and the transaction is committed. The program then fetches some statements from the repository using a direct call to the RepositoryConnection.getStatements(). The set of retrieved statements should contain the newly added statement since it matches the given pattern. The statement is then removed in a separate transaction.
The application can also be run against a remote repository exposed using the Sesame servlet container. In this case, the url parameter is used specify the sesame endpoint and this causes the config and repository parameters to be ignored. In order to use this, the following extra Apache and Sesame jar files must be included in the classpath (not provided with the OWLIM distribution):

commons-logging-1.1.1.jar
commons-codec-1.3.jar
commons-httpclient-3.1.jar
sesame-http-client-2.5.0.jar

There are Windows and Linux scripts (namely example.cmd and example.sh) prepared for convenience that execute the sample application using its default configuration and values.

Wordnet example

Wordnet, is the most popular lexical knowledge base, developed at the University of Princeton. It encodes the meanings of about 150,000 English words. The meanings of the words are defined by word-senses, which relate a word to a lexical concept. Lexical concepts are called synsets, i.e. synonym sets – about 115,000 of those appear in Wordnet v.2.0. Numerous lexical semantic relations are formally modelled, e.g.

  • Hyponymy (subsumption from a more-general term)
  • Antonymy (negation, a term with the opposite meaning)
  • Causation and entailment (for verbs)

A standard RDF/OWL representation of Wordnet is available at http://www.w3.org/TR/wordnet-rdf/. It contains about 1.9 million explicit statements (the Full variant), expressed in a fragment of OWL-Lite that further entails 6.3 million implicit statements.
To configure the getting started example program to use the Wordnet data sets and run the included Wordnet queries, one should download the archive of the full version from http://www.w3.org/2006/03/wn/wn20/download/wn20full.zip, extract it into a folder, e.g. ./preload/wordnet and provide a path to this folder using the preload command line parameter when starting the program. Some sample Wordnet queries are provided in the wordnet.serql and wordnet.sparql query files. These can be specified on the command line using the queryfile command line parameter.

Configuration

Sesame 2.0 keeps repository configurations in a SYSTEM repository – in RDF. A new repository can be configured simply by inserting an appropriate graph in to the SYSTEM repository. The getting started application uses the Turtle format for convenience and also because the Sesame console application uses the Turtle format for template files when creating repositories.
The diagram below gives a graphical illustration of an RDF graph that describes a repository configuration:

Often it is desirable to ensure that a repository starts with a predefined set of RDF statements, usually one or more schema graphs. This is possible by using the owlim:imports property. After start up, these files are parsed and their contents are permanently added to the repository. The complete set of configuration parameters, their descriptions and their default and allowed values are listed below. What follows is a short description of those properties specific to OWLIM-Lite that are used to setup the repository. For more information about Sesame 2 configuration schema refer to the Sesame documentation [5]. In short, the configuration is an RDF graph, the root node is of rdf:type rep:Repository, it must be connected through rep:RepositoryID property to a Literal that contains the human readable name of the repository. The root node must be connected via the rep:repositoryImpl property to a node that describes the configuration. The type of the repository is defined via rep:repositoryType property and its value must be openrdf:SailRepository to allow for custom sail implementations (such as OWLIM-Lite) to be used in Sesame 2.0. Then a node that specifies the Sail implementation to be instantiated must be connected with sr:sailImpl property. To instantiate OWLIM-Lite, this last node must have a property sail:sailType with the value swiftowlim:Sail – the Sesame framework will locate the correct SailFactory within the application classpath that will be used to instantiate the Java implementation class.
Namespaces corresponding to the prefixes used in the above paragraph are:

rep:   <http://www.openrdf.org/config/repository#>
sr:    <http://www.openrdf.org/config/repository/sail#>
sail:  <http://www.openrdf.org/config/sail#>
owlim: <http://www.ontotext.com/trree/owlim#>

All properties used to specify OWLIM-Lite's configuration parameters use the owlim: prefix and the local names match up with the parameters listed below, e.g. the value of the ruleset parameter can be specified using the http://www.ontotext.com/trree/owlim#ruleset property.
Many of the OWLIM specific configuration parameters can be set via the Java Virtual Machine (JVM) system properties passed as command line parameters when starting the JVM. Values for configuration parameters that are given on the command line take precedence over those present in the repository configuration. For instance, the ruleset parameter can be set from the command line by using:

-Druleset=owl-max

Sample Configuration

There follows an example configuration (in Turtle RDF format) of a Sesame 2 repository that uses a OWLIM-Lite sail implementation:

@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-max" ;
       owlim:partialRDFS  "true" ;
       owlim:noPersist "true" ;
       owlim:storage-folder "junit-storage" ;
       owlim:base-URL "http://example.org#" ;
       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://www.w3.org/2002/07/owl#"
     ]
   ].

Configuration Parameters

Almost all OWLIM parameters can be set both in the TTL configuration file and from the command line using the Java -D_<_param.name>=<value> command line option to set system properties. When a parameter is set simultaneously using both methods, the system property overrides the value in the configuration file. Some OWLIM parameters can only be set using system properties.
These list of all OWLIM parameters is here:

Parameter TTL Java -D Description
base-URL X X default <none>, specifies the default namespace for the main persistence file. Non-empty namespaces are recommended, because their use guarantees the uniqueness of the anonymous nodes that may appear within the repository.
contexts-index-size X X default 1000, specifies the size of the index for storing contexts.
debug.level   X default 0, defines the level of detail for debug output used for various implementation classes. Valid values are from 0 to 4 inclusive, where 0 is no debug output and 4 is the most verbose.
defaultNS X   default <empty>, default namespaces corresponding to each imported schema file separated by semicolon (
and the number of namespaces must be equal to the number of schema files from the imports parameter.
Example:

owlim:defaultNS "http://www.w3.org/2002/07/owl#;http://example.org/owlim#";
Note: This parameter cannot be set via a command line argument
entity-index-size X X default 1000000, defines the number of entity hash table index entries; the bigger the size, the less the collisions in the hash table and the faster the entity retrieval; the entity hash table does not rehash so its index size is constant throughout the life of the repository. The minimum value is 10000.
imports X   Default none, a list of schema files that will be imported at start up. All the statements, found in these files, will be loaded into the repository and will be treated as read-only. The serialization format is assumed to be RDFS/XML, unless the file has a .NT extension. Example:

owlim:imports
"./ont/owl.rdfs;./ont/ex.rdfs"

Schema files can be either a local path name, e.g. ./ontology/myfile.rdf
or a URL, e.g. http://www.w3.org/2002/07/owl.rdf
If this parameter is used then the default namespace for each imported schema file must be provided using the defaultNS parameter.
Note: This parameter cannot be set via a command line argument.
jobsize X X default 1000, the number of statements processed by each worker thread during a commit operation.
new-triples-file X X default <none>, the file used to store new triples on each commit. The filename used is a concatenation of storage-folder and this parameter.
noPersist     default false, if true, then changes to the repository are not persisted.
num.threads.run   X default <number_of_processors>, sets the number of worker threads used for parallel inferencing.
optimize.rules   X default false, used by the RuleCompiler to select the rule optimization method to use. true - use a method that orders the premises so that the premises with the smallest number of free variables are first. false - uses the more complex rule optimization technique.
partialRDFS (DEPRECATED) X X default false, if true then trivial RDFS inferences are switched off, such as 'every URI is type ' or 'every class is a sub-class of rdfs:Resource', etc. Deprecated in favour of explicit choice of rule-set, see ruleset below. However, if this flag is set to true then the chosen ruleset will effectively have -optimized appended to it if not present, e.g. ruleset=owl-horst and partialRDFS=true is the same as selecting ruleset=owl-horst-optimized
predicate-index-size     default 1000, the size of the index used to store predicates.
repository-type X X default in-memory-repository, available values are:
in-memory-repository
ruleset X X default owl-horst, built-in rule sets are empty, rdfs, owl-horst, owl-max, owl2-rl-conf and owl2-rl-reduced and their optimized counterparts rdfs-optimized, owl-horst-optimized, owl-max-optimized and owl2-rl-reduced-optimized (note that there is no optimised version of owl2-rl-conf). A custom rule set is chosen by setting the path to its rule file (.pie).
storage-folder X X default owlim-storage, specifies the folder where the repository contents will be persisted on shutdown (and reloaded on start up).
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