XML Companion, The, Third Edition

DTD declarations

When a DTD is in use, the xml:base attribute needs to be defined explicitly for each element it may be allowed to appear in:

<!ELEMENT collection  xml:base  CDATA  #IMPLIED>

When the element name is significant enough to imply a specific base location, this location can be inserted into the DTD as a default value:

<!ELEMENT image  xml:base CDATA "file:///d:/images/">

It is even possible that the value should never be changed, in which case it could be made into a fixed attribute value:

<!ELEMENT image  xml:base CDATA
                           #FIXED "file:///d:/images/">

Warning

These techniques should not be used if there is any possibility that the XML documents will be processed using parsers that do not validate them against a DTD or schema, or when ...