D Expansion of Entity and Character References (Non-Normative)

This appendix contains some examples illustrating the sequence of entity- and character-reference recognition and expansion, as specified in 4.4 XML Processor Treatment of Entities and References.

If the DTD contains the declaration

  <!ENTITY example "<p>An ampersand (&#38;#38;) may be escaped   numerically (&#38;#38;#38;) or with a general entity   (&amp;amp;).</p>" >  

then the XML processor will recognize the character references when it parses the entity declaration, and resolve them before storing the following string as the value of the entity " example ":

  <p>An ampersand (&#38;) may be escaped   numerically (&#38;#38;) or with a general entity   (&amp;amp;).</p>  

A reference in the document to " &example; " will cause the text to be reparsed, at which time the start- and end-tags of the p element will be recognized and the three references will be recognized and expanded, resulting in a p element with the following content (all data, no delimiters or markup):

  An ampersand (&) may be escaped   numerically (&) or with a general entity   (&).  

A more complex example will illustrate the rules and their effects fully. In the following example, the line numbers are solely for reference.

  1 <?xml version='1.0'?>   2 <!DOCTYPE test [   3 <!ELEMENT test (#PCDATA) >   4 <!ENTITY % xx '&#37;zz;'>   5 <!ENTITY % zz '&#60;!ENTITY tricky "error-prone" >' >   6 %xx;   7 ]>   8 <test>This sample shows a &tricky; method.</test>  

This produces the following:

• in line 4, the reference to character 37 is expanded immediately, and the parameter entity " xx " is stored in the symbol table with the value " %zz; ". Since the replacement text is not rescanned, the reference to parameter entity " zz " is not recognized. (And it would be an error if it were, since " zz " is not yet declared.)

• in line 5, the character reference " &#60; " is expanded immediately and the parameter entity " zz " is stored with the replacement text " <!ENTITY tricky "error-prone" > ", which is a well- formed entity declaration.

• in line 6, the reference to " xx " is recognized, and the replacement text of " xx " (namely " %zz ;") is parsed. The reference to " zz " is recognized in its turn , and its replacement text (" <!ENTITY tricky "error-prone" > ") is parsed. The general entity " tricky " has now been declared, with the replacement text " error-prone ".

• in line 8, the reference to the general entity " tricky " is recognized, and it is expanded, so the full content of the test element is the self-describing (and ungrammatical) string This sample shows a error-prone method.