Original text:
The syntax for the URI schemes in this section are specified using Augmented Backus-Naur Form (ABNF) RFC5234.  The definitions of <del> "host", "port", "path-abempty", and "query" are adopted from RFC3986. </del>  Section 8 (Multicast CoAP) in RFC7252 is not applicable to these schemes.

Reviewer comments:
Do we need to include the RFC7252 note for emphasis?
Probably not, as we are not changing anything about 5.10.1, are we? (But then 7.5 also points out a place where we maintain a property of 5.10.1.) ((But then, again, where would be put this?))
We need to identify the ABNF fragments as ABNF as in so they become easier to check in BAP.
We could add the note to Section 7, right after the new reference to "fragment":
Merged in abnf annotations from
is relevant to Section 7.
Good point. So I assume applying the same fix (add »[ "#" fragment ]«) four times to the ABNF in 7.1 to 7.4 would fix that? (We probably want to line-break before path-abempty in all four cases.)
If would be helpful to have more context for how the fragment identifier is used in CoAP. I don't see much detail in RFC7252 besides: Note: Fragments ([RFC3986], Section 3.5) are not part of the request URI and thus will not be transmitted in a CoAP request.
Fragment identifiers are not used in a transfer protocol; their use is a local matter on the client side. The mistake we made in RFC 7252 is providing ABNF that doesn't show fragment identifiers at all in the URI syntax. While CoAP as a protocol does not care about them, they are intended to be allowed in CoAP URIs so they can indeed be used on the client side. The note mentions this, but the ABNF does not reflect that. Same for coap-tcp-tls. Does it matter? The meaning of fragment identifiers is defined by the media type. So far, there has been little use of fragment identifiers in the media types being used with CoAP. Now, SenML actually does go ahead and defines a meaning for them, and other media types in the future might as well. So it would be good if the ABNF in the CoAP standards did not give the impression fragment identifiers cannot be used at all with CoAP URIs.
Note from Carsten: We may have to reopen that issue based on the about-face that the HTTP WG made here:
From URL which references: Absolute URI Some protocol elements allow only the absolute form of a URI without a fragment identifier. For example, defining a base URI for later use by relative references calls for an absolute-URI syntax rule that does not allow a fragment. absolute-URI = scheme ":" hier-part [ "?" query ] URI scheme specifications must define their own syntax so that all strings matching their scheme-specific syntax will also match the grammar. Scheme specifications will not define fragment identifier syntax or usage, regardless of its applicability to resources identifiable via that scheme, as fragment identification is orthogonal to scheme definition. However, scheme specifications are encouraged to include a wide range of examples, including examples that show use of the scheme's URIs with fragment identifiers when such usage is appropriate. and URL further states: Requirements for Permanent Scheme Definitions This section gives considerations for new schemes. Meeting these guidelines is REQUIRED for 'permanent' scheme registration. 'Permanent' status is appropriate for, but not limited to, use in standards. For URI schemes defined or normatively referenced by IETF Standards Track documents, 'permanent' registration status is REQUIRED. [RFC3986] defines the overall syntax for URIs as: URI = scheme ":" hier-part [ "?" query ] [ "#" fragment ] A scheme definition cannot override the overall syntax for URIs. For example, this means that fragment identifiers cannot be reused outside the generic syntax restrictions and that fragment identifiers are not scheme specific. A scheme definition must specify the scheme name and the syntax of the scheme-specific part, which is clarified as follows: URI = scheme ":" scheme-specific-part [ "#" fragment ] scheme-specific-part = hier-part [ "?" query ] On Jan 28, 2015, at 1:56 PM, Julian Reschke wrote: The answer is "no". URL I don't know how I got beaten into submission on that for RFC7230. ....Roy

Revised text:
The syntax for the URI schemes in this section are specified using Augmented Backus-Naur Form (ABNF) RFC5234.  The definitions of  <ins> "host", "port", "path-abempty", "query", and "fragment" are adopted from RFC3986. </ins> Section 8 (Multicast CoAP) in RFC7252 is not applicable to these schemes.