relational database example

Requirements

This example requires Java 7 or newer.
Download the following package graal-relational-database-example.zip and extract it where you want.

Build

Open a terminal and go into the extracted folder. Then, execute the following command:

javac -cp relational-database-example-1.3.1.jar fr/lirmm/graphik/graal/examples/relational_db/NaturalRdbmsExample.java

Run the example

Execute the following command:

java -cp relational-database-example-1.3.1.jar fr/lirmm/graphik/graal/examples/relational_db/NaturalRdbmsExample ./data/

What does this example do?

Create a KBBuilder:


  KBBuilder kbb = new KBBuilder();

Connect it to an SQLite database:


  kbb.setStore(new NaturalRDBMSStore(new SqliteDriver(new File(rootDir, dbFilepath))));

Load an ontology from lubm-ex-20.dlp file:


  kbb.addRules(new DlgpParser(new File(rootDir, ontoFilepath)));

Specify the approach to use to query answering (here priority to query rewriting):
```
  kbb.setApproach(Approach.REWRITING_FIRST);
    
```
Generate a knowledge base with this database and ontology:
```
  KnowledgeBase kb = kbb.build();
    
```
Create a DlgpWriter to print the results:
```
  writer = new DlgpWriter();
    
```

Parse and print a query:


  ConjunctiveQuery query = DlgpParser.parseQuery("?(X, Y1, Y2) :- "
      + " <Professor>(X),                                         "
      + " worksFor(X, <http://www.Department0.University0.edu>),  "
      + " name(X, Y1),                                            "
      + " emailAddress(X, Y2).");
  writer.write("\n= Query =\n");
  writer.write(query);

Query the KB and print the answers:


  writer.write("\n= Answers =\n");
  CloseableIterator results = kb.query(query);
  if (results.hasNext()) {
  	do {
  		writer.write(results.next());
  	} while (results.hasNext());
  } else {
  	writer.write("No answers.\n");
  }

Close resources:


  results.close();
  writer.close();
  kb.close();