Question: Of river tributaries of the Mississippi River, which is shortest?
Choices: Hudson River
Rhine
Amazon
River Thames
Ohio River
Danube
Mississippi River
Pirates of the Caribbean: Dead Man's Chest
Missouri River
Columbia River
SPARQL: SELECT ?e WHERE { ?e <pred:instance_of> ?c . ?c <pred:name> "river" . ?e_1 <tributary> ?e . ?e_1 <pred:name> "Mississippi River" .  ?e <length> ?pv . ?pv <pred:value> ?v .  } ORDER BY ?v LIMIT 1
Program:
function: Find
inputs: Mississippi River
function: Relate
dependencies: 0
inputs: tributary
forward
function: FilterConcept
dependencies: 1
inputs: river
function: SelectAmong
dependencies: 2
inputs: length
smallest
Answer: Ohio River