[tcs-lc] Question about XML attribute vs. element

[Richard Pyle]

What is the basic rule for when to designate something as an attribute,
rather than a separate element, in an XML schema?

Specifically, I'm thinking about "NomenCode" in TCS v095.  Right now, it
appears as an element within NameDetailed.  But why couldn't/shouldn't it be
represented instead as an enumerated attribute of NameDetailed?

Aloha,
Rich