Realization using d2rq

Overview

Underlying Structure and Procedure

  • D2RQ-Server is running on machine, using either Jetty or a servlet container (e.g. tomcat)
  • Server contains mapping ontology for mapping of a database (created before)
  • Machine is then accessed via http protocol in web-browser
  • RFD-data can be requested from D2RQ Server
  • yields view of RDF-structured linked data
  • SPARQL queries are supported by D2RQ
  • Browser may send SPARQL queries

Development Procedure:

  • Assuming a running server (e.g. localhost) with D2RQ-Server
  • Setup underlying Database
  • Create full Mapping
  • Reduce Mapping (when necessary): Extract relevant data
  • Start D2RQ-Server with Mapping
  • Use SPARQL queries to access data in browser

Example Usage Run

Setup DB

  • e.g. for sql dump file named "output2.sql"

  • authorization via: [username], [userPassword] and [dbName] for D2RQ on running [server]

    1. Create DB user:

      mysql -hlocalhost -uroot -prootpwd -e "CREATE USER '[username]'@'localhost' IDENTIFIED BY '[userPassword]'";

    2. Create DB:

      mysql -hlocalhost -uroot -prootpwd -e "CREATE DATABASE IF NOT EXISTS [dbName]";

    3. Set permission:

      mysql -hlocalhost -uroot -prootpwd -e "GRANT ALL ON [dbName].* TO '[username]'@'localhost'";

    4. Reload grant tables

      mysql -hlocalhost -uroot -prootpwd -e "FLUSH PRIVILEGES";

    5. Load DB

      mysql -hlocalhost -u[username] -[userPassword] [dbName] < output2.sql

Generate full Mapping

  • ./generate-mapping -u [username] -p [userPassword] -o mapping_[dbName]_full.ttl jdbc:mysql://127.0.0.1:3306/[dbName]

Adapt full Mapping

  • vi mapping_[dbName]_full.ttl
  • extract necessary fields
  • make sure to delete fields relevant to security (plain text passwords, answers to security questions, etc.)
  • Terminology of Ontology:
  • Triples of subject, predicate and object:
  • subject: instance of a class
  • predicate: RDF property
  • object: value of RDF property

Start Server with Jetty

Access Linked Data via SPARQL query

  • access SPARQL on running server in browser
  • e.g. localhost:8080/sparql
  • run SPARQL queries
  • optional: set limit (number of results shown)
  • review results