Here's a trivial SGML document:
<!doctype simp [
<!element simp o o (bit*)>
<!element bit - - (#PCDATA)>
<!attlist bit name id #required>
]>
<bit name=one>1</bit>
<bit name=two>2</bit>
And here's a picture of part of the grove that a conformant SGML parser (see the DSSSL spec. for details) should produce:
Copyright (c) Henry S. Thompson 1997
License to reproduce for any educational purpose is hereby granted, provided only that this copyright notice is reproduced in full as a part of any reproduction.