On 12/21/2017 07:31 AM, Niall O'Reilly wrote:
On 19 Dec 2017, at 7:09, Richard Gibson wrote:
1. "Domain name" is defined as «an ordered list of one or more
labels… identifying a portion along one edge of a directed acyclic
graph» (presumably starting at the root).
I'm not sure why one would presume to start there. As I read the
following fragment
of RFC 1034, the list of labels explicitly starts at the node of
interest and is read
towards the root.
|The domain name of a node is the list of the labels on the path from
the node to the root of the tree. By convention, the labels that
compose a domain name are printed or read left to right, from the most
specific (lowest, farthest from the root) to the least specific
(highest, closest to the root). |
Two reasons why I presume edge direction to be away from the root:
first, because it's consistent with the rest of the document in its
current form (for example, the very next sentence after my quoted text
describes how a fully qualified domain name "begins at the common root
of the graph"), and second, because parent-to-child directionality is
inherent to the DNS for delegations.
RFC 1034 seems to contemplate an undirected graph, so can happily use
towards-the-root for domain names and away-from-the-root for
delegations. But I don't think 7719bis has that luxury, because "domain
name" should remain valid even in a "naming system" without a single
common root.
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