5. Extensibly Marked Up

I'm new to XML (eXtensible Markup Language) but as I embark on an information career, I will need to be familiar with it. XML defines data and allows information to be moved from one place to another. It is used to organise information, such as in records management, for example, the Dublin Core Metadata Initiative, which is an international standard that ensures records can be shared or transferred and in archiving, the Encoded Archival Description (EAD) is the internationally recognised schema. XML is also used in bibliography and referencing packages such as EndNote and RefWorks, which enables resources to be transferred to other packages as well as word processing software.

I produced this list of magazines using XML. It's a very basic structure, having only the title, subject and date of issue as the categories. To improve the search and make it more detailed, I could also add a list of contents and writers/contributors and where the magazine is located.

XML is like a family. It contains one root element, the parent, while the elements below the root are the children. In this example, the root element is the magazine list and the child elements are the title, subject and date.

XML tags must be well-formed and valid otherwise the document will not display properly. Unlike HTML, XML must have open and closed tags and it has to contain consistent syntax. For example, if you use "yes" or "no", you cannot use other words such as "maybe".

A document type definition (DTD), describes the validity of the XML:

Working with XML and DTD requires a really good eye for detail. DTD is very limited as it's not flexible and it looks like a different language to XML, hence the XML Schema is becoming increasingly popular.