In your SGML documents or your DTD, within your SGML declaration, you can use the general delimiters NESTC and HCRO. NESTC stands for "NET-enabling start-tag close". NET stands for "Null End Tag". HCRO stands for "Hex Character Reference Open" delimiter.
You use the NESTC, or NET-enabling start-tag close, to close start tags and enable null end tags. For example:
DELIM NESTC "/"
specifies the use of "/" as the close of a start tag for an element that can end with a Null End Tag.
In combination with the example above, you could define the Null End Tag as follows:
DELIM NET ">"
Then you could enter an empty element tag EMPTY with only a start tag, as follows:
You use the HCRO, or Hex Character Reference Open delimiter, to open hex character references.
DELIM HCRO "&#x"
specifies the use of &#x as the delimiter for a hex character.
For the example above, you would mark two hex character elements as follows:
These general delimiters were specified in the SGML TC 2 (Technical Corrigendum #2).
These two general delimiters are not recognized unless they are defined in an SGML declaration. If NESTC is defined, then it is used, instead of a Null End Tag, at the end of a start tag that enables a NET end tag. If HCRO is defined, then hexadecimal numeric character references are allowed wherever decimal numeric character references are allowed.