Summary

n this chapter, we've got acquainted with a new important development, the eXtensible Markup Language, that, combined with a style sheet language, has a potential to eventually replace the heavily overused HTML of nowadays.  Being a simplified subset of SGML, XML allows you to create customized markup tags and specify the corresponding document strucure for any type of documents you may need to store or disseminate.  In particular, we have discussed the following topics:

• What XML is and isn't, in what aspects it is better than HTML, and why it is important to mark up the logical structure of a document in the first place;

• What are the well-formed XML documents and how they can be easily created from HTML documents;

• What are the advantages of providing an XML document with a DTD and how to refer to the DTD file from within an XML document;

• How elements and entities are declared in an XML DTD and then used in the documents;

• What linking capabilities are provided by the XML standard and how they extend the HTML hypertext model;

• What were the main goals of the creators of XML and in what ways its design principles help it compete with HTML and other technologies.