PREFIX country: <http://www.daml.ri.cmu.edu/ont/Country.daml#>
PREFIX cia: <http://ontolingua.stanford.edu/doc/chimaera/ontologies/world-fact-book.daml#>

SELECT ?name ?currency
FROM <http://www.daml.ri.cmu.edu/ont/Country.daml>
FROM <http://ontolingua.stanford.edu/doc/chimaera/ontologies/world-fact-book.daml>

WHERE 
{ 
  ?country country:name ?name.
  ?country country:cia ?ciaCountry
  OPTIONAL {?ciaCountry cia:HAS-MAIN-CURRENCY-TYPE ?currency.}
}
ORDER BY ?name