we are simply using in the DCF
<attributeoption attribute="xxx" dialoghidden="yes" screenhidden="no"/">
dialogHidden="yes" means the corresponding attribute is never shown in the Modify Attributes dialog so users have no way to modify it unless they hack via the "Edit selection as XML" or a text editor.
screenHidden="no" means it will be visible in the editing windows and they can use the "Insert Link" menu to create cross-references. However, the attribute value is not selectable thus copy and paste will not work. A workaround is to write some ACL code for the copy and hook that function to a menu or toolbar; alternative is to use a trick: first insert a cross-reference and then copy/paste the IDREF of the link rather than the ID of the target...HTH,
"Tout ce qui est impossible resteà accomplir" (Jules Verne)