Re: [urn] URI Scheme with Complex Equality Rules

Hi Ted,

Thanks for the reply.
I was thinking of a URI scheme instead of a URN NID, however,  it appears URI scheme requires that we create RFC which is a much more cumbersome process.

The OPC Foundation is author/maintainer of IEC 62541 and we are trying to fix the incorrect URN usage in the spec today.
The identifiers are used in the subjectAltName of X509 Certificates and uniquely identify the application that the Certificate is assigned to.

The uniqueness of our identifiers is within the scope of the system so an IP address can be system unique and static.
We specifically do not want to use ‘http’ because people tend to assume they are valid URLs with backing websites.

Regards,

Randy

From: Ted Hardie <ted.ietf@gmail.com>
Sent: Friday, August 26, 2022 10:08 PM
To: Randy Armstrong (OPC) <randy.armstrong@opcfoundation.org>
Cc: urn@ietf.org
Subject: Re: [urn] URI Scheme with Complex Equality Rules

Hi Randy,

Based on a skim of your use case, I can't yet see why minting a URI scheme would not work.

opcid://authority/parameters

The authority here would be the DNS name or IP address, and the definition of the scheme could establish that you wanted case insensitive matching for the parameters (where the context would be stored).  Is there something in IEC 62541 that would make this approach unviable? I admit that  I did not spend any francs to get it, so I don't have examples of what the context might look like, so if you have examples you can share, that would be useful.

Note that while URNs are guaranteed to be unique across the lifetime of an identifier, your scheme doesn't seem likely to want that, as it is relying on the DNS and IP address assignment, neither of which guarantees that property.

regards,

Ted

On Fri, Aug 26, 2022 at 1:47 PM Randy Armstrong (OPC) <randy.armstrong@opcfoundation.org<mailto:randy.armstrong@opcfoundation.org>> wrote:
I am sending this issue to this email as per the suggestion in RFC 8141.

The OPC Foundation (https://opcfoundation.org) has a need to uniquely identify OPC UA (IEC 62541) network resources but we do not want the complexity that comes with the various URN schemes.

Specifically we need:

  1.  Equality checks with case-insensitive string comparisons;
  2.  Human readable strings with uniqueness provided by a DNS name or IP address (always lower case).
  3.  A valid URI.
  4.  R/Q/F components not allowed.

We have been using urns of the form: urn:<dnsname>:<additional context>, however, this is not technically allowed by the URN RFC.
We do not want a syntax that needs to be parsed before any comparison can be done.

We could submit a request for our own nid but we don’t really have any syntax requirements other than the dns name and the case-insensitive string comparisons.

What is the best way forward?

Regards,

Randy Armstrong
OPC Foundation

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