bitmask.sparql

# Exploit named graphs to model associative arrays (i.e. Maps) in RDF
INSERT DATA {
  GRAPH eg:modeOfTransportation {
    eg:Bike      eg:hasBit 1 .
    eg:Car       eg:hasBit 2 .
    eg:Train     eg:hasBit 4 .
    eg:Airplane  eg:hasBit 8 .
  }
}

CONSTRUCT {
  eg:s eg:usesMode ?o
} WHERE {
  BIND(10 AS ?bitmask)

  # Convert the integer to
  # (1) a binary string representation, (2) split the string by each character into a JSON array
  # (3) reverse the order
  BIND(json:reverse(json:split(json:binaryString(?bitmask), "(?!$)")) AS ?bitarr)

  # Unnest each charactor ("0" or "1") with its array index
  ?bitarr json:unnest (?bitstr ?bitindex)

  # Filter out zero bits
  FILTER(?bitstr != "0")

  # Obtain the bit's corresponding decimal value (using Jena's power function)
  BIND(math:pow(2, ?bitindex) AS ?val)

  # Perform the lookup
  OPTIONAL { GRAPH eg:modeOfTransportation { ?o eg:hasBit ?val } } 
}