Re: [Uri-review] Request for URI schemes assigned to OPC UA

[Randy Armstrong <[e-mail]>]

The Application URI is the canonical identifier, however, it is simply an opaque string. There is nothing in OPC UA depends on the content of the value.  We simply use URI syntax because is a requirement for including the identifier in the subjectAltName of an x509 v3 certificate.


At this point I would like to know what is the benefit of registering anything? It seems like the main risk is the potential for accidental conflict with other uses of the same scheme. However, we would run into the same issue if our application was turned down and we used any existing scheme such as 'http' (which is the recommendation).

________________________________
From: Ted Hardie <[e-mail]>
Sent: Tuesday, May 23, 2017 9:20:57 AM
To: Randy Armstrong
Cc: Graham Klyne; [e-mail]; TCB
Subject: Re: [Uri-review] Request for URI schemes assigned to OPC UA

On Tue, May 23, 2017 at 9:03 AM, Randy Armstrong <[e-mail]<mailto:[e-mail]>> wrote:

The URN conforms  to:

https://tools.ietf.org/html/rfc2141


Other than that the specification leaves it up to the implementer to choose something globally unique.

RFC 3406, recently replaced by RFC 8141 go into the mechanics of URN registration.  Briefly, global uniqueness of the NID is maintained by a  global registry or URN namespace identifiers.

Implementers also have the option of using the http scheme as the application URI.

Is there a reason to register a URN scheme when we don't care about the content of the URN?

________________________________

I understood your message below indicated that the URN was the canonical name for the resources, with the individual network paths being linked to that URN.  Did I get that wrong?

regards,

Ted


From: Ted Hardie <[e-mail]<mailto:[e-mail]>>
Sent: Tuesday, May 23, 2017 8:34:50 AM
To: Randy Armstrong
Cc: Graham Klyne; [e-mail]<mailto:[e-mail]>; TCB

Subject: Re: [Uri-review] Request for URI schemes assigned to OPC UA

On Tue, May 23, 2017 at 5:30 AM, Randy Armstrong <[e-mail]<mailto:[e-mail]>> wrote:

1) We use the schemes for URLs that identify multiple network paths to a single resource which is identified with a URI that uses the 'urn' scheme. It is not clear to me that registration is required for this usage. Please advise.


Would you mind identify which URN nid you are using?  I did not see one listed here:

https://www.iana.org/assignments/urn-namespaces/urn-namespaces.xhtml#urn-namespaces-1

that was obvious.

regards,

Ted



2) The specs is an IEC specification as well (see https://webstore.iec.ch/publication/21993 ). In addition, the text quoted is old. Anyone can download the specifications from the OPC Foundation website today.













________________________________
From: Graham Klyne <[e-mail]<mailto:[e-mail]>>
Sent: Tuesday, May 23, 2017 2:07:11 AM
To: Randy Armstrong; [e-mail]<mailto:[e-mail]>
Cc: TCB
Subject: Re: [Uri-review] Request for URI schemes assigned to OPC UA

I have two objections here to permanent registration:

1. The specifications appear to be non-open "Note: Access to specifications and
developer resources are available to OPC Foundation members only."

2. The use of multiple URI schemes to access the same resource goes against
principles of web architecture [http://www.w3.org/TR/webarch/#uri-aliases].

This topic has been discussed previously on this list: see thread at [1].

[1]
https://mailarchive.ietf.org/arch/search/?email_list=uri-review&gbt=1&index=ze2I30iloSGZxlP2vAeCWcPOWus

#g
--



On 22/05/2017 22:04, Randy Armstrong wrote:
> Scheme name:
>
> opc.tcp       :  OPC UA Connection Protocol over TCP/IP
> opc.amqp  :  OPC UA Connection Protocol over AMQP
> opc.wss      :  OPC UA Connection Protocol over WebSockets
>
> We expect to add new schemes as time goes on.
>
> Status:  permanent
>
> Applications/protocols that use this scheme name:
>
> Applications which implement the OPC UA Connection Protocol defined by the OPC Unified Architecture specification:
> https://opcfoundation.org/developer-tools/specifications-unified-architecture
>
> The opc.tcp scheme has been in use in the field for about 10 years (we were unaware of the registration process).
> Note that the OPC Foundation has a trademark on the term "OPC" (see US Trademark #78732560)
>
> Contact:
> Randy Armstrong
> [e-mail]<mailto:[e-mail]>
>
> Change controller:
> OPC Foundation
> https://opcfoundation.org/
>
> References:
> The protocols and schemes are defined in Part 6: Mappings:
> http://www.opcfoundation.org/UA/Part6/
>
> _______________________________________________
> Uri-review mailing list
> [e-mail]<mailto:[e-mail]>
> https://www.ietf.org/mailman/listinfo/uri-review
>

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