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You can't avoid hearing about XML (Extensible Markup Language). Sometimes it
seems like everybody is talking about it. Trade journals, technical web sites and
business magazines are full of references to this new technology. There's so much
hype about XML that sometimes it's difficult to get a clear picture of just how this
technology can be harnessed to achieve useful and measureable business objectives.
This article will cut through some of that hype by providing a concise description of
what XML is, as well as showing two of the primary ways that it can be useful to businesses.
What is XML?
In practical terms, XML is a language for representing content in a structured manner.
Like HTML, the language in which web pages are created, XML is a markup language.
However, XML differs from HTML in that it is what is known as a metalanguage, or a
language for creating other languages.
This sounds complicated, so let's put it in perspective. HTML consists of a finite set of
element types, or tags, that can be used to record information about content. These
tags are referred to as markup. For example, HTML tags can be used to indicate that a
web browser should display some text in boldface, as shown below:
<b>This displays as bold on a web page.</b>
Since HTML consists of a finite set of tags, it stands to reason that it has limitations in
representing content. As an example, a web page may contain a phone number, but
there's no way in HTML to indicate what the content means. With HTML, a phone
number can be displayed in a particular font, in boldface or in a selected color, but
there's no way to explicitly state that this piece of information is a phone number.
Unlike HTML, XML lets you define your own markup elements. Thus, you can have tags
that have meaning within a designated knowledge area. XML will alow you to define
a <phone_number> tag to mark phone numbers within your documents. Representing
content in XML thus becomes a data modeling activity, much akin to relational
database design.
Another key feature of XML is that it encourages the separation of content and
presentation logic. The idea is that XML documents will contain content and tags that
describe the meaning of the content. Presentation logic is extracted into a style sheet,
a separate file that describes how the elements of an XML document should be
displayed.
How Can XML Be Useful to Businesses?
There are two primary ways in which XML can be useful to businesses:
- Content Reuse
- Communication
Content is a valuable commodity, and leveraging content in different ways can provide
significant advantages for companies. XML facilitates the reuse of content.
As an example, consider a newspaper that stores its news articles in XML. The
documents will contain tags that describe the meaning of the content, such as <headline>,
<byline>, etc. Presentation logic will exist in a separate style sheet.
This means that the newspaper company could have separate style sheets to display
an XML document in print media and on the web. The same news story, but used in
two different ways. The same content could also be easily reused in newsletters,
email marketing campaigns or news feeds to other companies.
XML also represents a valuable communication medium. The language promotes the
structured representation of content, with data elements that are meaningful within a
specified knowledge domain. This means one company can effectively provide content
to other companies, with no ambiguity in the meaning of the information.
Furthermore, since XML is a standard language, there are a wide variety of tools
available for processing and manipulating XML content. XML thus offers significant
advantages over proprietary data dissemination methods.
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