gabrielstein.org

XML, the Extensible Markup Language, is a W3C-endorsed standard for document markup. It defines a generic syntax used to mark up data with simple, human-readable tags. It provides a standard format for computer documents that is flexible enough to be customized for domains as diverse as web sites, electronic data interchange, vector graphics, genealogy, real estate listings, object serialization, remote procedure calls, voice mail systems, and more.

You can write your own programs that interact with, massage, and manipulate the data in XML documents. If you do, you’ll have access to a wide range of free libraries in a variety of languages that can read and write XML so that you can focus on the unique needs of your program. Or you can use off-the-shelf software, such as web browsers and text editors, to work with XML documents. Some tools are able to work with any XML document. Others are customized to support a particular XML application in a particular domain, such as vector graphics, and may not be of much use outside that domain. But the same underlying syntax is used in all cases, even if it’s deliberately hidden by the more user-friendly tools or restricted to a single application.

The first concept to understand XML files is understand Elements, Attributes and Character Data.

For example, if you have a table ‘person’ in a database with columns Id,Name, Age and Address, we can export this information using XML:

<person Id=”555″>
<Name> Gabriel </Name>
<Age> 28 </Age>
<Address> Street XYZ </Address>
</person>

In the first line, we have the element called ‘person’ with an attribute Id with a value ’555′. In the second, third and fourth line we have elements which receives the contents ‘Gabriel’, ’28′ and ‘Street XYZ’.
An element is delimited by the start-tag and the end-tag. Everything between the start-tag and the end-tag of the element (exclusive) is called the element’s content.

Example:
<Name> Gabriel </Name>

XML elements can have attributes. An attribute is a name-value pair attached to the element’s start-tag. Names are separated from values by an equals sign and optional whitespace. Values are enclosed in single or double quotation marks.

Example:
<person Id=”555″>

But… why use XML? For the basics, we can export database data, like table contents to our suppliers, partners and websites.
And more: there´s a lot of DBMS in the world. MySQL, Postgres, SQL, Oracle, DB2…
For now, you understood the basics of XML files, but we have a lot of things to learn, how make any DBMS export data to XML, how manipulate data on XML files…

But… stay calm… we will discuse this topics on anothers posts.

Well.. see you on another post!

*DBMS – Database management system