<sch:rule context="tei:*[@calendar]"> <sch:assert test="string-length( normalize-space(.) ) gt 0"> @calendar indicates one or more systems or calendars to which the date represented by the content of this element
belongs, but this <sch:name/> element has no textual content.</sch:assert> </sch:rule>
The type attribute may be used to distinguish different kinds of ‘origin’, for example original
place of publication, as opposed to original place of printing.