Constraints

You can create SPARQL query constraints using the Expressions class which provides static methods to create Expression objects representing SPARQL's built-in expressions:

Variable name = Spanqit.var("name");
Expression<?> regexExpression = Expressions.regex(name, "Smith");
System.out.println(regexExpression.getQueryString());
// ==> REGEX( ?name, "Smith" )

Expressions take Operand instances as arguments. Operand is implemented by the types you would expect (Variable, the RDF model interface RdfValue, and Expression itself). Where possible, Expressions has included wrappers to take appropriate Java primitives as parameters as well:

Variable price = Spanqit.var("price");
Expression<?> priceLimit = Expressions.lt(price, 100);
System.out.println(priceLimit.getQueryString());
// ==> ?price < 100

For those places where a wrapper has not (yet) been created, RdfLiterals can be used instead. The Rdf class provides factory methods to create StringLiteral, NumericLiteral, and BooleanLiteral instances:

Variable price = Spanqit.var("price");
ExpressionOperand discount = Rdf.literalOf(0.9);
Expression<?> discountedPrice = Expressions.multiply(price, discount);
System.out.println(discountedPrice.getQueryString());
// ==> ( ?price * 0.9 )

The RDF Model >