An XML document contains XML Elements.
An XML element is everything from (including) the element's start tag to (including) the element's end tag.
An element can contain:
In the example above, <bookstore> and <book> have element contents, because they contain other elements. <book> also has an attribute (category="CHILDREN"). <title>, <author>, <year>, and <price> have text content because they contain text.
XML elements must follow these naming rules:
Any name can be used, no words are reserved.
Make names descriptive. Names with an underscore separator are nice: <first_name>, <last_name>.
Names should be short and simple, like this: <book_title> not like this: <the_title_of_the_book>.
Avoid "-" characters. If you name something "first-name," some software may think you want to subtract name from first.
Avoid "." characters. If you name something "first.name," some software may think that "name" is a property of the object "first."
Avoid ":" characters. Colons are reserved to be used for something called namespaces (more later).
XML documents often have a corresponding database. A good practice is to use the naming rules of your database for the elements in the XML documents.
Non-English letters like йтб are perfectly legal in XML, but watch out for problems if your software vendor doesn't support them.
XML elements can be extended to carry more information.
Look at the following XML example:
Let's imagine that we created an application that extracted the <to>, <from>, and <body> elements from the XML document to produce this output:
Don't forget me this weekend!
Imagine that the author of the XML document added some extra information to it:
Should the application break or crash?
No. The application should still be able to find the <to>, <from>, and <body> elements in the XML document and produce the same output.
One of the beauties of XML, is that it can be extended without breaking applications.
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