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Vocabularies

Network RDF Query Facility

The aim of the project is to create RDF Query Facility, - repository and query engine which

provides networked access to RDF databases based on RMI protocol and EJB specification
allows to utilize in RDF repositories knowledge from knowledge bases
1. extend predicate set of query language using predicate defined in KB
can be easily integrated with prolog to use it for reasoning and for assert facts into running prolog application
use semantic information about RDF classes and properties in search operations

The NRQF is based on Jena - RDF parser and query engine from HPL (Hewlett-Backard Labs)

1 Simple RMI wrapper over Jena query engine

Online demonstration.

Javadoc documentation Source/binary/doc .

Makes possible to run Jena QueryEngine as RMI server

There is no need to parse RDF model for each application/execution of application.

Example:

1 to run database

1 run rmiregistry

2 run java JenaQueryServer

the RMI RDF Query Facility will be operating on rmi://yourcomputerIP:1099/JQF

2 to load RDF model:

A from Interactive Client

       1 run "java JQFClient", then in prompt

connect 127.0.0.1:1099

load http://yourRDFfileaddress

B from any application

connect to RDF Query Facility: IJenaQueryFacility jqf = (IJenaQueryFacility)Naming.lookup("rmi://yourserverIP:1099/JQF");

load model:

if (jqf.getState().equals(IJenaQueryFacility.state_loaded)){
                 // model is already loaded
} else {
   try {
           jqf.loadModel(modelURL);

          // model loaded
   } catch (Exception e) {
   // exception handling
}

3 to query database

A from interactive client

       1 run "java JQFClient", then in prompt

connect rdfserverIP:1099

select ...

now in client select should be in small letters and all query in one paragrah. will be solved soon

B from application

    ArrayList results = jqf.query(command);

// command is RDQL string

// Array list is array list of rows of result set, each row is ArrayList of values

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