When and where to apply a field rule
You can use field rules to determine work item type behavior regardless of the state of the work item. For example, a field that is required for a bug that is new and active remains required until the bug is closed.
Field rules can also be scoped to certain states, transitions, and even reasons. The complete set of rules that apply to any particular field is additive from the following four subsets:
Work item type-specific
You can apply scope to field rules by using the FIELDS and FIELD (Workflow) elements within the STATE, TRANSITION, and REASON elements.
When you list fields in the workflow, specify only the field reference name.
The following example defines the following rule: When a bug is in the Active state, do not allow the customer severity field to be modified.
<STATE name="Active"> <FIELDS> <FIELD refname="MyCorp.Severity" > <READONLY /> </FIELD> </FIELDS> </STATE>