Example: XHTML 1.0

• Large DTDs often have elements with the same attributes
• Entity declarations would be of use within the DTD itself (syntactic sugar: the "%" in the entity declaration means that the entity should be used within the DTD, using the "%" rather than the "&" character)
• XHTML 1.0 Recommendation largely consists of the DTD!
• Eg, the h1 definition:

  <!ENTITY % coreattrs 
    "id    ID    #IMPLIED
     class CDATA #IMPLIED
     style CDATA #IMPLIED
     title CDATA #IMPLIED"
  >
  ...
  <!ENTITY % attrs "%coreattrs; %i18n; %events;">
  ...
  <!ENTITY % inline "a|%special;|%fontstyle;|%phrase;|%inline.forms;">
  <!ENTITY % Inline "(#PCDATA | %inline; | %misc;)*">
  <!ELEMENT h1 %Inline;>
  <!ATTLIST h1
    %attrs;
  >