difficulties working with xml-data

advantages of xml

Xml has become the leading technology for data-exchange because of it's advantages:

• Xml is well readable for humans and computers. It is an open standard. It can be read and written by any simple text-editor.
• Xml-files can contain complex data-structures.
• Xml-interfaces can easily be changed.
  • New elements can be added.
  • Programs reading this modified interface simply overread the new elements.
  • The programms do not crash!
• Xml-elements have not to be positioned on a special line or column.
• The order of xml-elements is normally not relevant.

But: Standard unix-tools do not work with xml-data!

The advantages of xml turn into disadvantages, because standard unix-tools like "diff", "cmp", "sort", "join" and "comm" do not work correct with xml-files. Look at the following examples:

example 1

The following two files are contentwise equal. only the order of the elements is completely different. A standard compare-tool will be not aware of this. It will always will find differences, although the files are cotentwise equal.

example 2

The "<name> and "<firstname>" of the person are in both files equal.
But in file "test2b.xml" there is no element "<birthdate>".

If you compare these two files for example with "diff"-utility, you cannot exclude element "<birthdate>" from comparison.