N/A
So we have another short overview of xml for you to look at:
What is XML you ask? (confused? no worries..)
XML was designed to transport and store data.
HTML was designed to display data.
Before you continue you should have a basic understanding of the following:
What is XML?
- XML stands for EXtensible Markup Language
- XML is a markup language much like HTML
- XML was designed to carry data, not to display data
- XML tags are not predefined. You must define your own tags
- XML is designed to be self-descriptive
- XML is a W3C Recommendation
The Difference Between XML and HTML
XML is not a replacement for HTML.
XML and HTML were designed with different goals:
- XML was designed to transport and store data, with focus on what data is.
- HTML was designed to display data, with focus on how data looks.
HTML is about displaying information, while XML is about carrying information.
XML Does not DO Anything
Maybe it is a little hard to understand, but XML does not DO anything. XML was created to structure, store, and transport information (content).
The following example is a note to Tove from Jani, stored as XML
<note> <to>Romeo</to> <from>Juliet</from> <subject>wherefore art thou</subject> <body>Deny thy father and refuse thy name</body> </note>
But still, this XML document does not DO anything. It is just pure information wrapped in tags. Someone must write a piece of software to send, receive, and/ or display it. (again that code is describe/defined in the database on the other end).The note above is quite self descriptive. The xml tags <from> <to> etc, simply added context and meaning to the data, which I describe through what I do with that data on my server side data base system (mysql + php). It has sender and receiver information, it also has a heading and a message body.
In other words… XML is Just Plain Text
XML is nothing special. It is just plain text. Software that can handle plain text can also handle XML.
However, XML-aware applications can handle the XML tags specially. The functional meaning of the tags depends on the nature of the application.
With XML You Invent Your Own Tags
The tags in the example above (like and ) are not defined in any XML standard. These tags are “invented” by the author of the XML document.
That is because the XML language has no predefined tags.
The tags used in HTML (and the structure of HTML) are predefined. HTML documents can only use tags defined in the HTML standard (like /p, p,/p h1, etc.).
XML allows the author to define his own tags and his own document structure.
XML is Not a Replacement for HTML
XML is a complement to HTML
It is important to understand that XML is not a replacement for HTML. In most web applications, XML is used to transport and define data, while HTML is used to format and display the data.
My best description of XML is this:
XML is a software- and hardware-independent tool for carrying information.
XML is a W3C Recommendation
XML became a W3C Recommendation in February, 1998.
XML is Everywhere
- We have been participating in XML development since its creation. It has been amazing to see how quickly the XML standard has developed, and how quickly a large number of software vendors has adopted the standard.
- XML is now as important for the Web (especially the social Web)as HTML was to the foundation of the Web.
- XML is the most common tool for data transmission between all sorts of applications, and is becoming more and more popular in the area of storing and describing information.
The last item on the list for this learning cycle is to read more about XML and follow a short tutorial found at W3C Schools and take their short self-study quiz.
After, we should be ready for the next cycle where we introduce content management systems… most of which are based on php and xml.