Center for Archival Resources On Legislatures (CAROL)

Foundations: XML

Introduction to XML

XML is a hardware- and software-independent structured language and format designed to structure, store, transport, and facilitate presentation of data. XML is the most common tool for data transmissions between all sorts of applications.

The World Wide Web Consortium (W3C) uses the following to describe XML through w3schools.com:

• XML stands for EXtensible Markup Language.
• XML is a markup language much like HTML.
• XML was designed to carry data, not to display data.
• XML tags are not predefined. You must define your own tags.
• XML is designed to be self-descriptive.
• XML is a W3C Recommendation.

The W3School's XML Basic Tutorial summarizes the characteristics of XML that often make it an appropriate standard to use. The tutorial states the following:

XML Simplifies Data Sharing

In the real world, computer systems and databases contain data in incompatible formats. XML data is stored in plain text format. This provides a software- and hardware-independent way of storing data. This makes it much easier to create data that can be shared by different applications.

XML Simplifies Data Transport

One of the most time-consuming challenges for developers is to exchange data between incompatible systems over the Internet. Exchanging data as XML greatly reduces this complexity, since the data can be read by different incompatible applications.

XML Simplifies Platform Changes

Upgrading to new systems (hardware or software platforms), is always time consuming. Large amounts of data must be converted and incompatible data is often lost. XML data is stored in text format. This makes it easier to expand or upgrade to new operating systems, new applications, or new browsers, without losing data.

XML Makes Your Data More Available

Different applications can access your data, not only in HTML pages, but also from XML data sources. With XML, your data can be available to all kinds of "reading machines" (Handheld computers, voice machines, news feeds, etc), and make it more available for blind people, or people with other disabilities.

Project Resources

The project team worked on a number of fronts related to XML. Links to these are provided below.

• XML Basics (NOTE: This takes you out of the CAROL Resource Center.)
• XML Usage Survey February 2009 (pdf)
• Legislative Metadata Schema
• XML Native Database white paper December 2009 (pdf)
• XML Native Database pilot project August 2009-January 2010 (NOTE: This takes you out of the CAROL Resource Center.)

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February 15, 2012; links verified March 29, 2013.