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What is XML?
XML stands for extensible markup language. A markup language is a set of codes, or tags, that describes the text in a digital document. The most famous markup language is hypertext markup language [HTML], which is used to format Web pages. XML, a more flexible cousin of HTML, makes it possible to conduct complex business over the Internet.
What are XML’s advantages over HTML?
Whereas HTML tells a browser application how a document should look, XML describes what’s in the document. In other words, XML is concerned with how information is organized, not how it is displayed. [XML formatting is done through separate style sheets.]
To illustrate, consider the following HTML tags: the command
signals a paragraph and word translates into word. The HTML tags are fixed; every site developer uses the same tags to do the same things. XML, by contrast, lets you create your own tags to label the meaning or use of data. So if you’re using XML to describe a widget you’re selling, your tags might look like this: $100” SKU=“555432” dealer=“Widgets Incorporated”>.
XML’s flexibility has many benefits. It lets you transfer data among corporate databases and Web sites without losing crucial descriptive information. It lets you automatically customize the presentation of data rather than display the same page to all comers. And it makes searches more efficient because search engines can sort through precise tags rather than long pages of text.
What are the business applications of XML?
Because XML brings sophisticated data coding to Web sites, it helps companies integrate their information flows. By creating a single set of XML tags for all corporate data, information can be shared seamlessly among Web sites, databases, and other back-end systems. But the revolutionary power of XML lies in supporting transactions between businesses. When a company sells a good or service to another company, a great deal of information needs to be exchanged—about prices, terms, specifications, delivery schedules, and so on. HTML’s one-size-fits-all nature makes such exchanges difficult, if not impossible, over the Internet. With XML, all the necessary information can be shared electronically, allowing complex deals to be closed without any human intervention. That’s why business-to-business Web markets, such as those run by Ariba and Commerce One, already rely on XML to automatically match buyers and sellers. In the not-too-distant future, your company may be judged by the content of its XML tags.
But if individual companies create their own tags, how will they share information with one another?
That’s the risk of flexibility. Without a standardized syntax, one company may create unique tags that are unrecognizable to its suppliers and buyers. To reduce that danger, many XML dictionaries are being created in fields like finance, mathematics, chemicals, and e-commerce. Embedded in XML, these dictionaries standardize tag definitions. On Wall Street, for example, JP Morgan and PricewaterhouseCoopers recently proposed FpML, a dictionary that would standardize the XML tags for foreign currency exchange and other financial transactions. Similar efforts are under way in other industries.
A version of this article appeared in the July–August 2000 issue of Harvard Business Review.
XML is a software- and hardware-independent tool for storing and transporting data.
What is XML?
- XML stands for eXtensible Markup Language
- XML is a markup language much like HTML
- XML was designed to store and transport data
- XML was designed to be self-descriptive
- XML is a W3C Recommendation
XML Does Not DO Anything
Maybe it is a little hard to understand, but XML does not DO anything.
This note is a note to Tove from Jani, stored as XML:
Tove
Jani
Reminder
Don't forget me this weekend!
The XML above is quite self-descriptive:
- It has sender information
- It has receiver information
- It has a heading
- It has a message body
But still, the XML above does not DO anything. XML is just information wrapped in tags.
Someone must write a piece of software to send, receive, store, or display it:
Note
To: Tove
From: Jani
Reminder
Don't forget me this weekend!
The Difference Between XML and HTML
XML and HTML were designed with different goals:
- XML was designed to carry data - with focus on what data is
- HTML was designed to display data - with focus on how data looks
- XML tags are not predefined like HTML tags are
XML Does Not Use Predefined Tags
The XML language has no predefined 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.
HTML works with predefined tags like
,