XMLXML is a format for storing structured information that looks a lot like HTML. (See an example.) Because XML lets us create tags like <author> and <distance>, XML files can be understood by both humans and machines. XML can also represent hierarchical structures which are awkward to represent in a relational database. XML has been used as the basis for many file formats, such as SVG, VoiceXML, WAP, and XHTML. Many organizations have developed XML formats for internal use, and because it's a standard, it's a great way for organizations to share data. For example, RSS lets web sites share headlines and articles and ebXML is a standard for business-to-business electronic commerce.
Web ServicesWeb Services are one of the most important developments in XML. Web services are web applications that are meant to be used by software programs rather than by people. For instance, web services can be used to connect a graphical front-end program that runs on an ordinary computer or a wireless device to a database-backed server application. Web services also allow web applications to communicate, enabling a new generation of web applications. Some web sites, like epinions.com have even based their internal infrastructure on web services.
People have been using http to transmit machine-readable information for a long time, but XML-RPC and SOAP provide stanards that link many different operating systems, web servers, and programming languages. Thanks to support from big vendors like Microsoft and IBM, SOAP has gotten the lion's share of hype -- however, quite a lot of interesting applications of XML-RPC have developed in the Open Source world, such as an interface to KDE that allows scripting in any language and the Red Hat Network uses XML-RPC to automatically update software package on computers running Red Hat Linux.
What we can doOver the years, working with new technologies is one of the things that we've done best -- we've been working with XML since it was introduced. We've written about XML, developed our own XML vocabularies, and used emerging standards such as VoiceXML. We're always looking for new challenges.