Noun compounds don't have a clear annotation

[omriabnd]

In many schemes many of them would be considered MWEs. In UCCA unanalyzable is only reserved to extreme cases, which leaves cases like "Jewish religion" or "master class" w/o one clear annotation.

[nschneid]

There is definitely a lot of gray area with noun compounds. "Jewish religion" to me is not an MWE because you could substitute any religion, whereas "master class" is an MWE as an idiomatic way to say advanced form of instruction. (But certainly less opaque than "hot dog".)