<element attribute-name = "attribute-value">....</element>
The value of an attribute needs to be quoted, even if it contains only numbers. An example
<car color = "green">volvo</car>
The same information can also be defined without using attributes: <car>
<brand>volvo</brand> <color>green</color>
</car>
When possible try to avoid attributes. Data structures are more easy described in XMLtags.
Software that checks XML-documents can do a better job with tags than with attributes.