How is data structured in XML?

XML is tag-based. Every element has a start tag and an end tag, such as <interface>…</interface>, and elements nest inside each other to build a tree.

The Extensible Markup Language is widely used in web services and in network protocols such as NETCONF. A list of users looks like this:

<users>
  <user>root</user>
  <user>Jason</user>
  <user>Jamie</user>
  <user>Luke</user>
</users>

The rules that matter:

• Each element opens with <name> and closes with </name>, and the data or child elements sit between the two.
• Elements nest: the users section contains four user elements, which gives the data its structure.
• Tags can carry attributes and namespaces (xmlns="…"), which NETCONF uses to say which data model an element belongs to.

XML is precise and self-describing, but verbose: every name appears twice.

Go deeper:

• XML — Wikipedia — syntax, namespaces and schemas.