XML is programmable, hierarchical data. It is designed to be similar to HTML in terms of ease of use and similar to SGML in terms of power, extensibility, and expressiveness.
You can translate XML documents into other formats by using XSLT. Often the target format is HTML, but it does not have to be. Translating between divergent document formats is also quite common.
DTDs and XML schemas help ensure that an XML document is not only well formed but also valid. A document can be well formed and still have invalid data in it. It's up to a validating XML parser to check the document against its DTD or XML schema to ensure that it contains valid data.
DOM is a popular API for processing XML documents as objects. Put succinctly, DOM loads an ...