Defining Work Item Type Fields
Work Item forms use fields to display data, or to let users input data or select options. You control the appearance and behavior of fields on work item forms by defining those fields in the work item type definition.
In the work item type definition, define a field by specifying a name, a reference name, and a type. Fields can also be defined to include Help text, to follow rules, and to exhibit specific reporting behavior.
<FIELD refname="System.Title" name="Headline" type="String" reportable="Dimension"> <!-- Field Help Text and Rules go here --> </FIELD>