Attribute:
        ...
	{IndexAttribute} '[' indices+=AttributeIndex (',' indices+=AttributeIndex)* ']';

AttributeIndex:
	{WildcardIndex} '*' |
	{NumberIndex} index=JSONNUMBER (':' to=JSONNUMBER (':' step=JSONNUMBER)?)? |
	{ExpressionIndex} '(' expression=Expression ')' |
	{ConditionIndex} '?' '(' expression=Expression ')';

terminal JSONNUMBER returns ecore::EFloat: // Definition according to JSON standard
	'-'? ('0' | ('1'..'9') DIGIT*) ('.' DIGIT+)? (('E' | 'e') ('+' | '-')? DIGIT+)?;

terminal fragment DIGIT:
	('0'..'9');