Missing tags/elements when downloading from OSM XAPI and OSM API

The relevant fields are <node>, <way>, and <relation>, in that order, and lots of them, all enclosed in a big <osm>...</osm> section. Anything else is superfluous and won't be processed by most applications anyway.

I believe, the original question hasn't really been answered yet, which was, why there's no bounds element in the XAPI response. Let's take a closer look.

After all, the XAPI call to the following URL will be translated into something Overpass API can make some sense out of, notably an Overpass XML request.

So, if you query for something like

overpass.osm.rambler.ru/cgi/xapi_meta?*[bbox=27.9314,-26.1841,28.1538,-26.0028]

this will in fact be translated into the following Overpass XML query under the hood:

<query type="node">
  <bbox-query s="-26.1841" n="-26.0028" w="27.9314" e="28.1538"/>
</query>
<union>
  <item/>
  <query type="way">
    <bbox-query s="-26.1841" n="-26.0028" w="27.9314" e="28.1538"/>
  </query>
  <recurse type="way-node"/>
</union>
<print mode="meta"/>
<query type="relation">
  <bbox-query s="-26.1841" n="-26.0028" w="27.9314" e="28.1538"/>
</query>
<print mode="meta"/>

BTW: You can get to this translated query on your own, if you're following the XAPI Compatibility Layer to Overpass XML / QL migration procedure, as outlined in the wiki.

That's already a good starting point to feed into overpass turbo: http://overpass-turbo.eu/s/eAf

Now, how do we get the bounds element into the query result?

You need to know that this requires something called global bounding box, which can be added by providing an <osm-script> element along with a bbox attribute. Your resulting query looks like this: it's basically the same overpass turbo query as before, but this time also returning a bounds element.

http://overpass-turbo.eu/s/eAh

You can get the query results from overpass turbo via Export -> get raw data directly from Overpass API, you'll end up with a file called interpreter and the following line in the resulting file:

 <bounds minlat="-26.1841" minlon="27.9314" maxlat="-26.0028" maxlon="28.1538"/>

Mission accomplished!