Computer science

Computer science
a paper on XML, does not need to be very fancy I just need to answer these questions:

1 What is XML?
2 Why XML?
3 Features of XML
4 Difference between XML and HTML
5 Rules for writing a XML Document.
6 What is a well formed XML Document?
7 What is a valid XML Documents
8 What are the two types of XML definitions?
9 What are the meaning of all symbols such as *? +, |, ATTLIST, REQUIRED, IMPLIED, etc.
10 What is XPath?
11 How to draw a tree structure? Write a XPATH expression.
12 How to write a simple XML documents based on the tree structure.