Use of boolean property value in a form.
From semantic-mediawiki.org
Fragment of a discussion from Help talk:Type Boolean
Hmm, these booleans. I am not sure but this rather looks like an issue with the Semantic Forms extension. I'd give it a shot at the respective talk page. Do not forget to indicate the versions of MW, SMW and SF as well as PHP you are using. There is no need to quote the code as long as you point to line 67. Cheers