rdfSymbPairs :: GenParser Char st [(IRI, Maybe IRI)]
rdfSymbPairs = uriPair >>= \ u -> do
    commaP `followedWith` uriP
    us <- rdfSymbPairs
    return $ u : us
  <|> return [u]
rdfSymbPairs :: GenParser Char st [(IRI, Maybe IRI)]
rdfSymbPairs = uriPair >>= \ u -> do
    commaP `followedWith` uriP
    us <- rdfSymbPairs
    return $ u : us
  <|> return [u]
rdfSymbPairs = uriPair >>= \ u -> do
    commaP `followedWith` uriP
    us <- rdfSymbPairs
    return $ u : us
  <|> return [u]