Improper tag use?

I’ve been working on a project involving cleaning and auditing OSM data for a Udacity online class. I’ve come across a large number of ways which appear to be tagged incorrectly according to the documentation in the OSM Wiki. Specifically, these elements have been tagged with building=terrace and landuse=residential, and they all appear to be patios or terraces adjacent or attached to private homes. There are about 2,000 of them. Am I correct in understanding that this way of tagging these elements is not in compliance with the documentation? Should they be corrected? What would be the proper way to tag them?
Roke (pronounced “rocky”) Whitson

Maybe you are right, and we need some work on that issue.

So first tell us in what area you have seen these objects. The we can do some inspections, with JOSM validator or Overpass-Turbo.

After that we need a decision whether that data has really wrong tagging, and if yes, how we can correct that. There are established tools / methods for that.

First things first, yes there are things in OSM that are by any community standard “incorrectly tagged”. What this usually means is that the original mapper didn’t know or didn’t understand the options available (and that’s quite possible if wiki pages, forum and list posts and help site questions aren’t in their first language).

However, please don’t rely on the wiki (or the JOSM validator, or the various QA sites) as being always “correct” either. The information there should be a guide only - the best way to tell what something should be tagged as is to actually go there in person and have a look at it.

Where there are what look to be genuine tagging problems (like “building=terrace” applied to a patio) then in the first instance I’d contact the original mapper and politely explain the problem. OpenStreetMap isn’t primarily a “data” project; it’s a “people” one, and your message about potentially incorrect tagging needs to be designed to encourage the person that receives it to tag things correctly in the future.

The more difficult question is what to tag these sort of areas as. That’s probably a question for the tagging list or perhaps a national list forum if they’re all in one country (such as this thread in the German forum).