parid0927 | Sun, 19 Jan 2003 16:17:10
In a well-formed topic map graph, only a-nodes serve as "A" endpoint types, only c-nodes serve as "C" endpoint types, only r-nodes serve as the "R" endpoint types, and only t-nodes serve as the "T" endpoint types. There is no such thing as an "x-node", because all kinds of nodes are eligible to serve as the x endpoints of Cx arcs. The exceptional character of the x endpoints of Cx arcs is the reason why "x" is the only endpoint type name that is always rendered in lower case.
A topic map graph has four different types of nodes, a-nodes (A), c-nodes (C), r-nodes (R), and t-nodes (T). Each of these nodes can serve as the "x" end of a "Cx" arc, therefore is no x-node. (When "x" is the endpoint of an arc, it is rendered in lower case as a signal of its special character.)
While it may seem more precise to say "a-nodes serve as the "A" endpoint type" it seems rather verbose and possibly confusing. From my reading of the draft, there is no different between an a-node and the "A" endpoint type. I can't have one without the other, so if there is some advantage in the extra words I am not seeing it.