With no explanation, label each line with "O", "art-broadcastprogram", "art-film", "art-music", "art-other", "art-painting", "art-writtenart", "building-airport", "building-hospital" or "building-hotel" preceded by ":".
Periodically
people
and
carriages
tumbled
into
what
had
become
little
more
than
an
open
sewer
.
Periodically:O
people:O
and:O
carriages:O
tumbled:O
into:O
what:O
had:O
become:O
little:O
more:O
than:O
an:O
open:O
sewer:O
.:O