Right now there are lots of things Mapnik does not know how to render - which Mapnik handles by not rendering them at all.
Until these tags are handled, I suggest users can add an extra tag to tell Mapknik what to render as, something like;
leisure=dog_park
mapnik_render:leisure=park
or
shop=outdoor
mapnik_render:shop=convenience
Otherwise it is tempting to only use tags that make things visible, even though they are incorrect (which I have seen).
Also the tags can be automatically removed later on, when they are supported.
– Sasq