XML: The Free, Extensible Language for Data Description, Slides of Database Management Systems (DBMS)

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Introduce of XML

What is XML?

• XML stands for E X tensible M arkup L anguage
• XML is a markup language much like HTML
• XML was designed to describe data
• XML tags are not predefined. You must define

your own tags

• XML uses a Document Type Definition (DTD)

or an XML Schema to describe the data

• XML with a DTD or XML Schema is designed to

be self-descriptive

One Example of XML

• Tom
• Jane Reminder
• Don't forget me this Weekend!

**This XML document does not DO anything. It is just

pure information wrapped in XML tags. Someone must write a piece of software to send, receive or display it.

XML is free and extensible

• XML tags are not predefined. You must "invent" your own tags.
• The tags used to mark up HTML documents and the structure of HTML documents are predefined. The author of HTML documents can only use tags that are defined in the HTML standard (like

  ,

  , etc.).
• XML allows the author to define his own tags and his own document structure.
• The tags in the example above (like and ) are not defined in any XML standard.

XML can Separate Data from HTML

• With XML, your data is stored outside your HTML.
• When HTML is used to display data, the data is stored inside your HTML. With XML, data can be stored in separate XML files. This way you can concentrate on using HTML for data layout and display, and be sure that changes in the underlying data will not require any changes to your HTML.
• XML data can also be stored inside HTML pages as "Data Islands". You can still concentrate on using HTML only for formatting and displaying the data.

XML is used to Exchange Data

• With XML, data can be exchanged between

incompatible systems.

• In the real world, computer systems and databases

contain data in incompatible formats. One of the most time-consuming challenges for developers has been to exchange data between such systems over the Internet.

• Converting the data to XML can greatly reduce this

complexity and create data that can be read by many different types of applications.

XML can be used to Store Data

• With XML, plain text files can be used to

store data.

• XML can also be used to store data in files or

in databases. Applications can be written to

store and retrieve information from the

store, and generic applications can be used to

display the data.

XML can make your Data more Useful

• With XML, your data is available to more

users.

• Since XML is independent of hardware,

software and application, you can make your

data available to other than only standard

HTML browsers.

• Other clients and applications can access

your XML files as data sources, like they are

accessing databases.

• must All XML elements have a closing tag

This is a paragraph

This is another paragraph

• XML tags are case sensitive

This is incorrect

This is correct

• All XML documents must have a root element --All XML documents must contain a single tag pair to define a root element. --All other elements must be within this root element.

.....

• Attribute values must always be quoted

Tom

Jane

• Comments in XML

• There is nothing special about XML

--There is nothing special about XML. It is just plain text with the addition of some XML tags enclosed in angle brackets.

--Software that can handle plain text can also handle XML.

Data Binding

• Empire Burlesque Bob Dylan USA Columbia 10.90 1985

• Hide your heart Bonnie Tyler UK CBS Records 9.90 1988

• Greatest Hits Dolly Parton

XML in future Web development

• XML is going to be everywhere.
• It has been amazing to see how quickly the XML

standard has been developed and how quickly a large number of software vendors have adopted the standard.

• XML will be as important to the future of the Web

as HTML has been to the foundation of the Web and that XML will be the most common tool for all data manipulation and data transmission.