---+ SPARQL TODO List

* Complete SORT BY:
	* Compare order in test-cases
	* Value-specific comparison
	* Compare expression results (e.g., ASC(?a+?b))

* Implement value based semantics in xsd:dateTime

* { ?x ?y 1 } cannot be mapped to rdf(X, Y, literal(type(xsd:integer, '1')))
  because it must match :a :b "01"^^xsd:integer.

* Does SPARQL define a total ordering of literals?  If so, we may use
  this for the literal AVL-tree and speedup some of these queries a
  lot.