An abstract syntaxt of a sample document structure

Article		::= <article> (Paragraph | Picture) article>
Paragraph	::= <para> <TEXT> para>
Picture		::= <figure> <BITMAP> Paragraph figure>
<TEXT>		::= ASCII string
<BITMAP>	::= OCTET string

The coding of the abstract syntax

<article>	::= ASCII-CHARS
		    ( `<' `a' `r' `t' `i' `c' `l' `e' `>' )
article>	::= ASCII-CHARS
		    ( `<' `/' `a' `r' `t' `i' `c' `l' `e' `>' )
...
ASCII string	::= /* All ascii characters */
OCTET string	::= /* a string of 8-bit bytes */

This is a sample document using the abstract syntax and coding in Xa and Xb

<article> 
   <para>
      This is a sample of some paragraphs.
      This is the first.
   para>
   <para>
      And this is the second.
   para>
   <figure>
      ........................
      ........................
      <para>
         Figure 1. And here is the figure of the article.
      para>
   figure>
article>