[Tagging] objects mixing linear and area (for ex fence and landuse)

[Yves]

>While it's obvious to a human when looking at the rendered object, it's
>rather difficult to write software to interpret this clearly: an object is
>supposed to be an area or a line, not both
>-- Joseph Eisenberg

OSM elements are rarely interpreted independently of their tags, so I won't be so sure about this one. Of course if a data consumer is to do half of the job, then it's their choice. 
Yves