added options for describe algorithms (#30)

SparqlLexer.g4

@@ -37,6 +37,10 @@ CARD_EST_REDUCTION_FACTOR: ('C'|'c')('A'|'a')('R'|'r')('D'|'d')'_'('E'|'e')('S'|
 CARD_EST_MIN_CARDINALITY: ('C'|'c')('A'|'a')('R'|'r')('D'|'d')'_'('E'|'e')('S'|'s')('T'|'t')'_'('M'|'m')('I'|'i')('N'|'n')'_'
                           ('C'|'c')('A'|'a')('R'|'r')('D'|'d')('I'|'i')('N'|'n')('A'|'a')('L'|'l')('I'|'i')('T'|'t')('Y'|'y');
 
+CONCISE_BOUNDED_DESCRIPTION: ('C'|'c')('B'|'b')('D'|'d');
+
+DESCRIBE_DIRECT: ('D'|'d')('I'|'i')('R'|'r')('E'|'e')('C'|'c')('T'|'t');
+
 BASE : ('B'|'b')('A'|'a')('S'|'s')('E'|'e');
 
 PREFIX : ('P'|'p')('R'|'r')('E'|'e')('F'|'f')('I'|'i')('X'|'x');

SparqlParser.g4

@@ -72,7 +72,7 @@ constructQuery
     ;
 
 describeQuery
-    : DESCRIBE (varOrIRI+ | '*') datasetClause* whereClause? solutionModifier
+    : DESCRIBE describeAlgorithm? (varOrIRI+ | '*') datasetClause* whereClause? solutionModifier
     ;
 
 askQuery
@@ -95,6 +95,10 @@ cardinalityEstimation
     : Q_HINT_CARD_EST (CARD_EST_REDUCTION_FACTOR|CARD_EST_MIN_CARDINALITY)
     ;
 
+// NOT PART OF THE OFFICIAL GRAMMAR (tentris specific)
+describeAlgorithm
+    :  (CONCISE_BOUNDED_DESCRIPTION|DESCRIBE_DIRECT)
+    ;
 
 varOrBlankNode
     : var | blankNode