Well, it always depends on your application 
It seems to me that you mainly have more general questions about the XML Schema built-in-datatypes.
So the link below might be helpful for you.
http://www.w3.org/TR/xmlschema-2/#built-in-datatypes
Here you will a find a graph, showing the inheritance structure of XML Schema built-in datatypes.
If you click on a certain datatype, you will get more information about value space, constraining facets and also sample values.
Best regards,
Peter
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