What is XML ?
Keywords : web, website, design, browser, HTML, XHTML, XML, XSL, DTD.
Summary: XML means "Extensible Markup Language". It is a general-purpose markup language for documents containing structured information designed to transport and store data. Although HTML and XHTML appear to have similarities in their syntax, they are significantly different in many ways, they were designed for different purposes : HTML is about displaying information, while XML is about carrying information. XML is a W3C (short for World Wide Web Consortium- the international governing body for the development of platform independent web standards and specifications) recommendation.
It used to take me 10 minutes to design a web site. When I began designing
web sites back in 1996, the process was very simple. I would ask the person who had requested
the web site to put all of their content into a Microsoft Word file and email it to me.
I would copy and paste that content into FrontPage or a text editor, insert some HTML tags
to create the layout, add some graphics for style and I was finished.
Wireless technology
put the kibosh on my plan to make a decent living working 30 minutes per day for the rest
of my life. Beginning in 1998 or 1999, every wireless electronic gadget under the sun now
came equipped with full access to the internet and email. Web browsers and email client
software were installed on laptops, palm tops, cell phones, and computer screens in automobiles,
to name a few.
The platforms and web browsers being used on wireless products are different
from an ordinary desktop PC. These new systems are not fully compatible with many
elements of the HTML programming language. As a result, websites created exclusively
with HTML are often invisible or inaccessible to the wireless user.
The programming community responded by creating cross-platform compatible languages
and specifications for creating web sites so that all sites could be viewed equally,
or at least close to equally, on all web browsers. A language called XML was created to define
data without telling the browser how to display it. HTML forced the browser to display data a certain way.
XML defined data without telling the browser how to display it because XML was a simple text file.
Thus, data created with XML could be viewed on any machine, computer, or browser. Then, specifications
such as XHTML and XSL were developed in order to turn XML files into web pages that had style and structure,
and more importantly, could be viewed and interpreted across all platforms, wireless or not.
Now that you understand how and why web design has changed, you are ready to learn about the main
topic of this article, XML Schema. XML Schema is a specification that enables a programmer to describe
the structure of an XML document. Programmers used to rely on Document Type Definition (DTD) to structure
their XML documents, but XML Schema is now seen as the permanent replacement for DTD. XML Schema was initially
introduced by Microsoft, and was later endorsed and adopted by the World Wide Web Consortium (W3).
XML Schemas ensure that data can be communicated in a format that is universal. For example, different
countries use different formats to display the date. Some countries put the month first, others put
the day first, and some put the year first. The XML Schema for date requires that all dates be in YYYY-MM-DD format.
Thus, everyone viewing XML data knows what the data is because they know it is written in XML Schema. XML Schema
has a lot of built-in data types for defining data. To define data, XML Schema uses attributes.
XML Schema attributes are somewhat similar to HTML attributes in that they are included within a tag,
and the attribute further defines the tag. With HTML, an image tag would have a source attribute to provide the
name of the file that contains the image to be displayed. Another example of an HTML attribute would be an
alignment attribute within a paragraph tag that stipulates whether the paragraph should be aligned to the left or
right.
Examples of XML Schema attributes for describing data are string, decimal, boolean, integer, date, and time. One
of the most important features of XML Schema is that it is replete with many different built-in restrictions that can
be imposed on all data so that data is consistently displayed a certain way or presented in a certain format.
Using XML Schema restrictions, a programmer can impose limits on upper or lower bounds for ranges of numbers,
the length of numbers or the length of lists of items, and XML Schemas can even be used to define how white
space is handled (tabs, line feeds, etc.).
XML Schema and XML programming are not easy to learn. You might want to start by searching for some basic online
tutorials, but if web design is your full-time profession, you should instead enroll in some courses offline
at a local college or computer programming institute. If you do not make use of versatile languages such as
XML, XSL, and XHTML, your website might be invisible to those who surf the web on wireless devices, and you might
be putting your career as a web designer in jeopardy.
Source: Article Directory
Jim Pretin is the owner of http://www.forms4free.com, a service that helps programmers make email forms., a service that helps programmers make email forms.
Resources :
W3C page about Extensible Markup Language (XML)
XML Tutorial (W3C)
