XML is a standard, definded by W3C.
Ideally, XML encoding shoudl be UNICODE, supporting ALL languages available.
The more powerful usage of xml: the tag can be other languages than English, too! (localized content is widely seen and shuold be reflected as standard.)
URI = URL + URN
Identifier can be other than “within the browser”, think of The book, email, telephone number.
Even RFC number or geolocation! However please specify the protocol so other will understand WTH you’re talking.
RSS, Atom feed, ODF (OOXML is not XML), SVG. All defined by XML.
XML: Used everywhere
XML hell, B2B interchanged data, web feed, whatever!
Some basic rules:
Move along, see some other good site!
Attr. Vs. Elem.
Attribute is more trivial than element, Attribute can contain only CDATA, Element can contain whatever.
XML: Price to pay
Document are <very>long</very>. They are overwhelmed with
<unnecessary> <nested> <and> <also> <clumsy>tags</clumsy> </also> </and> </nested> </unnecessary>
Also, you have to compromise < > ! & “ character with yet-another-special strings to replace these.
Content & Child Element can be lived within one branch
<div> Some text goes here. This is the content <ul> <li>And some list goes here</li> <li>and yet another list element</li> </ul> </div>
Mixed or Messed content?
Not so well-structured. However you can see this as “document“, more natural to XML.
Well-formed Vs. Valid
Well – formed = Pass the XMLness rules.
Valid = Well-formed + Conformed with DTD / Schema.
How about Schemas?
DTD: Old classic schemas. 11 years. Simpler, but less power.
XSD: Overpass DTD weakness, currently as W3C Recommendation. More complicated and more power.
Even valid one might be useless. Semantics concern
XML had nothing to do with semantics. Users DO! Ill-semantic document is crap, nobody would understand it.
HTML Vs. XML: The fundamental different
HTML is about Presentation, mainly for human consumption.
XML is about Structure, machine understandable.
The more detailed different can be found EVERYWHERE. Go ahead and googled it.