nit: it's a WebSGML thing eg. an XML feature factored in to the revised SGML spec for accomodating XML-style empty elements, which was necessary so that XML could be DTD-less, yet still have a compact idiom for empty elements.
Classic SGML only had a shortform syntax such as
<elmt/content of elmt/
and WebSGML introduced NETC and EMPTYRM to extend this into a (rather idiosyncratic) way of achieving support for XML-style empty elements within the SGML framework.
Classic SGML only had a shortform syntax such as
and WebSGML introduced NETC and EMPTYRM to extend this into a (rather idiosyncratic) way of achieving support for XML-style empty elements within the SGML framework.