There are situations where many data elements need to be captured in a specific context on the interview, but the interview looks clumsy when they are all displayed together.
The «DropDownPanel()» command enables the template author to group various controls together so that they appear only when the user selects to show them. The way this works is that the data element controls are placed on a panel in almost exactly the same way that they appear on the interview panel itself, but this panel only becomes visible when the user chooses to display it. An example of a drop down panel before and after displaying would be:
All of the data elements referenced can have their various properties set in other parts of the document (such as Caption, Heading, Footing, AlignCaption, etc.). The Contact_Details data element is regarded as a place holder, much like that described in “The PlaceHolder Command”, and can be used so that a Caption or Heading or Footing or other property can be attached to the drop down panel. But the data element Contact_Details will not appear in the data set after the interview has completed.
In the template that produced the above drop down panel, the data element Postal_Address is subject to the condition that the Send_by_SnailMail control has been checked. If it were not checked, then the Postal_Address control would not appear. This is normal behaviour according to the XpressDox relevance rules.