The following string, which is used as an example string two times in 'Modularization of XHTML™' [1] as well as two times in 'XHTML™ Modularization 1.1' [2], omits the required exclamation mark:
]] <ENTITY % MODULE.img.myattr.qname "%MODULE.pfx;myattr" > [[ (Explanation: Instead of "<!ENTITY" the text says "<ENTITY".) [1] http://www.w3.org/TR/2001/REC-xhtml-modularization-20010410/xhtml-modularization [2] http://www.w3.org/TR/xhtml-modularization/xhtml-modularization -- With regards, Leif Halvard Silli