# XML Guide * * * ## XML - EXtensible Markup Language XML is a cross-platform, software- and hardware-independent tool for transmitting information. ## XML Document Example Tove Jani Reminder Don't forget me this weekend! * * * ## What is XML? * XML stands for _EXtensible Markup Language_ * XML is a _markup language_ much like HTML * XML is designed to _describe data_ * XML tags are not predefined. You need to _define your own tags_. * XML uses a _Document Type Definition (DTD)_ or _XML Schema_ to describe the data. * XML with a DTD or XML Schema is designed to be _self-descriptive_. * XML is a W3C Standard * * * ## XML Does Not Do Anything XML itself does nothing. XML creates structure, stores, and carries information. The example XML document above is a note written from Jani to Tove. Note the heading and the body. It also has information about where it came from. However, this XML document does nothing. It is just information wrapped in XML tags. Someone must write software to send, receive, or display it: **MESSAGE** **To:** Tove **From:** JANI Don't forget me this weekend! * * * ## XML Tags Are Not Predefined XML tags are not predefined. You must "invent" your own tags. The tags used to mark up HTML documents are predefined. HTML authors can only use tags that are defined in the HTML standard (like `

`, `

`, etc.). XML allows the author to define his/her own tags and his/her own document structure. In the example above (like `` and ``), the tags are not defined in any XML standard. These tags are "invented" by the XML document author. (#) (#) (#) ## How to Learn XML? (#)