Adding SELECT content

Several methods allow to add elements in the SELECT part of the SPARQL request:

• The SPARQLRequest.addSelect(String var) method adds a variable to use in the SELECT part of the request. Return true if the variable could be added (which means it was not already defined in the WHERE part of the request)
• The SPARQLRequest.addSelect(String... variables) method adds a list of variables to use in the SELECT part of the request
• The SPARQLRequest.setSelect(String... variables) method sets the list of variables to use in the SELECT part of the request
• The SPARQLRequest.addSelect(Expression expr, String asVar) method adds an expression to use in the SELECT part of the request. Return true if the variable could be added (which means it was not already defined in the WHERE part of the request)
• The SPARQLRequest.setSelectAll() method sets the "SELECT *" construct
• The SPARQLRequest.hasSelectVariable(String var) method returns true if a variable is alsready part of the SELECT

Selects with all

The syntax SELECT * is an abbreviation that selects all of the variables that are in-scope at that point in the query.

The following example uses a "SELECT *":

   SparqlRequest request = new SparqlRequest("sitac");
   request.setSelectAll();
   request.addType("zone", "TaskZone");
   request.addPropertyValue("zone", "isTasked", true);   

Will return the following SPARQL content:

   SELECT *
   WHERE {
      ?zone rdf:type sitac:TaskZone .
      ?zone sitac:isTasked "true" .
   }

Selects with variables

The following example uses a SELECT with a variable:

   SparqlRequest request = new SparqlRequest("sitac");
   request.addSelect("zone");
   request.addType("zone", "TaskZone");
   request.addPropertyValue("zone", "isTasked", true);   

Will return the following SPARQL content:

   SELECT ?zone
   WHERE {
      ?zone rdf:type sitac:TaskZone .
      ?zone sitac:isTasked "true" .
   }

Selects with expression

The following example uses a SELECT with an expression:

   SparqlRequest request = new SparqlRequest("sitac");
   request.addSelect("zone");
      
   VariableExpression varExpr = new VariableExpression("altitude");
   FunctionExpression function = new FunctionExpression(FunctionExpression.FUNCTION_FLOOR, varExpr);
   request.addSelect(function, "alt");
   request.addType("zone", "Zone");
   request.addPropertyRef("zone", "hasAltitude", "altitude");  

Will return the following SPARQL content:

   SELECT ?zone (floor(?altitude) AS ?alt)
   WHERE {
     ?zone rdf:type sitac:Zone .
     ?zone sitac:hasAltitude ?altitude .
   }