Steven Seida D2RQ Blog Integration Lab

Data to RDF Integration Approaches* 1 of 2 *Summarized from Ch 9 of Semantiic Web Programming, 2009, by Hebeler et al.. Starting PointApproachNotes XML dataDevelop XSLT transformation code (RDF is, after all, XML) Code is generally short and simple, although learning curve is high and changes to source XML structure may cause need for new XSLT. XML dataUse Java XML bindings (JAXB) to get data into Java structures, then write a template for Velocity to write as RDF Provides Java to perform any transformations in data and moves RDF generation into configuration files although changes to XML structure likely to cause recompile. Relational Database Use D2RQ (or SquirrelRDF or OpenLink Virtuoso) to expose data via SPARQL Small learning curve, but RDF tends to mirror database structure.

Data to RDF Integration Approaches (2 of 2) Starting PointApproachNotes Custom dataDevelop Turtle (N3) writer for the structure (say in Java). Very flexible approach, but entirely custom and when kept simple does no data cleaning. Java structuresUse Java Reflection (ability to query classes for method names, etc) to auto create (serialize) classes of each object type and properties of each attribute. No configuration required, so very quick although little customization can occur in the output.

D2RQ Exercise Use D2RQ to provide access to a blog database in Jena.

D2RQ Review Database to RDF Query (D2RQ) Converts database information into RDF triples Generally wants to make classes and properties 1. Create mapping file (auto-generates a starter) 2. Use mapping file for conversion -Can convert entire database -Can leave database and provide SPARQL endpoint

Configure MySQL with a Blog DB 1.Add “blog” database to your mySQL database 1.Connect as root (lakers), create database blog; exit; 2.Load an example blog database with a schema (and data) from file wordpressdump.sql at windows command prompt* 1.mysql -u root -plakers blog < wordpressdump.sql 1.This command must result in an empty/blank response. 3.Download and install d2r-server (d2r-server-0.7) to c:\extra\ 1.Select Download from berlin.de/bizer/d2rq/ 4.Create a mapping file. In the D2R server directory issue the command to generate a mapping file*: 1.Syntax is: generate-mapping [-u username] [-p password] [-d driverclass] [-o outfile.n3] [-b base uri] jdbcURL 2.generate-mapping -u root -p lakers jdbc:mysql:// /blog > blog.n3 1.Specifying the mysql driver is optional 2.The result file is blog.n3 (inspect it) *A space or not a space after –p is very important and irritating.

D2RQ Concepts Top Line of Mapping File: “map:” Defaults to URL of output filename -> Change this to anything (because will be a prefix), but you probably don’t want it to match Vocab. “Vocab:” line -> This is your RDF ontology and instances prefix. Change to Two primary concepts in D2RQ are: 1. ClassMap -> what classes to create 2.PropertyBridge ->what relationships to create

MySQL tables in Blog The blog schema is for WordPress (i.e. wp) mysql> show tables; | Tables_in_blog | | wp_comments | | wp_links | | wp_options | | wp_postmeta | | wp_posts | | wp_term_relationships | | wp_term_taxonomy | | wp_terms | | wp_usermeta | | wp_users | rows in set (0.00 sec) Fields in wp_posts post_author post_date post_date_gmt post_content post_title post_excerpt post_status... In looking at your mapping file, what is D2RQ saying should be a class? What does it say should be RDF properties?

Browsing with D2RQ Open C:\extra\d2r-server-0.7\doc\index.html in a browser Scroll down that page about half-way: We have finished step 3, “generate a mapping file,” now perform steps 4 and 5: Start the server: d2r-server blog.n3 Test the Server -> Open in a web browser. Look around at the data (in html). -Who is the writer of the first two posts?

SPARQL Query in Jena Make a copy of your Lab3_2 project Make (and load) your model using: Model d2rqModel = new ModelD2RQ(mappingFile); -where mappingFile is the filename of the mapping file -Also add d2rq-0.7.jar from the d2r-server*/lib area to your project -Get rid of the model loading, timing, etc. Then issue a SPARQL query and output (useful) results to XML for*: 1.All the property data (and values) about all users**. 2.All the property data about users that have issued postings. *Hovering your mouse over the rdf:type for instances in the localhost:2020 web page can show the actual type names. *Does the d2r-server you started on the preceding page need to be running for your SPARQL to work?

Other Questions What steps are required to enable a database with D2RQ? What Jena constructs are required to access a D2RQ store? What do we do if we want joined tables to be the class instances (and properties)? Does D2RQ provide us a persistence mechanism?

Backup

Optional: MySQL with Non-Root User 1.Inside mysql Add “blog” database with user “blogger” with password “noise” to your mySQL database 1.Connect as root, create database BLOG; 2.create user blogger identified by ‘noise’; create databse blog; 3.grant all privileges on blog.* to identified by ‘noise' with grant option; 2.Load the blog database with a schema (and data) in file wordpressdump.sql (run at windows command line): 1.mysql -u blogger -pnoise blog < wordpressdump.sql 3.Install d2r-server to c:\extra\ (then run a shell in the d2r-server* directory) 4.Create a mapping file. In the D2R server directory issue the command to generate a mapping file: 1.generate-mapping [-u username] [-p password] [-d driverclass] [-o outfile.n3] [-b base uri] jdbcURL 2.generate-mapping -u blogger -p noise jdbc:mysql:// /blog > blog.n3 1.The mysql driver is optional 2.The result file is blog.n3

How to dump a MySQL database To Dump the blog database using credentials for user blogger (with password noise), run the following at a command line: mysqldump -u blogger -pnoise blog >wordpressdump.sql (Note: There is no space between –p and noise) How to restore same database and credential, run the following: mysql -u blogger -pnoise blog < wordpressdump.sql (Note: that the blog database must already exist with blogger as a user and there is not space between –p and noise.)