Re: [regext] Extension Prefixes, JSON Values, and URI Path Segments

[Mario Loffredo <[e-mail]>]

Hi Jasdip,

please find my comments embedded.

Il 31/05/2022 22:20, Jasdip Singh ha scritto:
> Hi Mario,
>
> Few comments, and one suggestion.
>
> Thanks,
> Jasdip
>
> On 5/30/22, 4:50 AM, "Mario Loffredo" <[e-mail]> wrote:
>
>      Hi Jasdip,
>
>      the current approach appears unpractical to me as it results in managing
>      all the changes in the same manner regardless their scope.
>
> [JS] Consistency is the key point. Per the Breakage Analysis section in the RDAP Extensions Analysis doc I had shared earlier [1], the current approach -- tight coupling between extension identifier and rdapConformance value -- seems to afford us zero collisions and near-zero breakage for various change scenarios, and that should be a good thing, no?. To your point, yes, there are few scenarios (especially during transition for an extension vis-à-vis an existing path without that extension identifier in it) where sending data for both the old and new extension identifier in a response sounds inefficient but that's the trade-off with a consistent, collision- and breakage-free extension model.
>
> [1] https://docs.google.com/document/d/1iadJc1D2-z_9pSy0PNcl4mhEQglh7dIHhbmRgrCW6mc/edit?usp=sharing

[ML] Approach A will raise breakage issues as, at least according to a 
strict interpretation of what is stated in the existing RFCs, every 
change will result in replacing old features with new ones through a 
deprecation process.

I agree with you that it will be consistent and collision-free but In my 
opinion it will introduce more complexity for both clients and servers 
whereas things could be managed straightforwardly.

Tom has replied to this objection of mine presenting some workarounds 
that could be used to figure out some use cases without necessarily 
starting a deprecation procedure.

Nevertheless, it seems to me those workarounds require the handling of 
additional features beyond those involved by the change itself (e.g. in 
the case of a non breaking change to response extension, the usage of a 
specific field containing the conformance value).

REST API implemeters are well aware that breaking changes should be 
avoided as far as possible. Most of changes to REST services consist in 
adding new features rather than deleting, replacing or changing old ones.

That being agreed , can't really understand why we should go in the 
opposite direction and  basically reset the gains from using REST and, 
above all, JSON.

Most of version changes could be signaled on server side by simply 
adding a value in the rdapConformance array instead of dealing with a 
deprecation process and providing clients with information about sunset 
and complete replacement of old features.

>
>      A unified apporach is always advisable except in those cases where it
>      results in adding complexity where it is unneeded. And I suspect  that
>      this would be one of those cases.
>
>      Indeed, handling every change (at least reading strictly the RFCs)
>      through a transition process would be a mess for server operators.
>
> [JS] It doesn't look like we need any extraneous transition process beside listing the from and to extension identifiers in the rdapConformance array. Please see below one plausible way for jcard-to-jscontact transition using solely the current approach.
[ML] Think that deprecations are tricky and transition processes should 
be used carefully and only when the change to the REST API is relevant 
such as the replacement of jCard with JSCard.
>
>      Let's imagine, for example, how a possible non-breaking change in
>      JSContact representation impacting on the RDAP response could be managed
>      while the possible transition from VCARD to JSContact was still in place.
>
>      Server operators may have to deal with a transition within another
>      transition ?!?!
>
> [JS] One plausible way for jcard-to-jscontact transition using solely the current approach (tight coupling):
>
> Phase 1: Only jcard
> ---------------------------
>
> p = entity/<handle>
>
> {
>    “rdapConformance” : [
>      “rdap_level_0”
>    ],
>    {
>      …,
>      "vcardArray" : [
>        …
>      ]
>    }
> }
>
> Phase 2: jscard_0 extension (available along with jcard)
> ---------------------------------------------------------------------------
>
> p = entity/<handle>
>
> {
>    “rdapConformance” : [
>      “rdap_level_0”,
>      “jscard_0”
>    ],
>    {
>      …,
>      "vcardArray" : [
>        …
>       ],
>      “jscard_0” : {
>        …
>      }
>    }
> }
>
> Phase 3: no_jcard extension (jcard data no more in response)
> -----------------------------------------------------------------------------------
>
> p = entity/<handle>
>
> {
>    “rdapConformance” : [
>      “rdap_level_0”,
>      “jscard_0”,
>      “no_jcard”
>    ],
>    {
>      …,
>      “jscard_0” : {
>        …
>      }
>    }
> }
>
> Phase 4: jscard_1 extension (has a new field beside the jscard_0 data)
> ---------------------------------------------------------------------------------------------
>
> p = entity/<handle>
>
> {
>    “rdapConformance” : [
>      “rdap_level_0”,
>      “jscard_0”,
>      “no_jcard”,
>      “jscard_1”
>    ],
>    {
>      …,
>      “jscard_0” : {
>        …
>      },
>      “jscard_1” : {
>        …,
>        “new_field” : …
>      }
>    }
> }
>
> Phase 5: Transition from jscard_0 to jscard_1 after a sufficient grace period for clients
> -------------------------------------------------------------------------------------------------------------------
>
> p = entity/<handle>
>
> {
>    “rdapConformance” : [
>      “rdap_level_0”,
>      “no_jcard”,
>      “jscard_1”
>    ],
>    {
>      …,
>      “jscard_1” : {
>        …
>      }
>    }
> }
>
>      Non-breaking changes can be more easily managed and signaled by server
>      operators by adding a minor version in rdapConformance array and an
>      optional link to the related documentation in the response. That's it.

[ML] The rdap-jscontact draft defines two query parameters to make an 
RDAP server return only one between JSCard and jCard.  I consider it a 
valuable choice as it restricts  the response payload (significantly for 
search response) and permits clients to receive JSCard only when they 
are ready to process it.

That apart, your example represents the scenario where the transition 
from jscard_0 to jscard_1 comes later the transition from vcardArray to 
jscard_0,  not simultaneously.

Anyway, if returning three times almost the same considerable 
information wouldn't be likely, returning it twice would occur each time 
JSCard (or even jCard) was changed.

>
> [JS] One suggestion. To help settle and/or move forward the discussion vis-a-vis if we should stick with the current approach (tight coupling), or evolve using the proposed approach (lack of tight coupling), it would be great if we could review and discuss the Breakage Analysis section in https://docs.google.com/document/d/1iadJc1D2-z_9pSy0PNcl4mhEQglh7dIHhbmRgrCW6mc/edit?usp=sharing and decide whether the breakage points matter for various change scenarios or not.

[ML] By a strict interpretation of Approach A, every change would result 
in a replacement of something. Since replacing a feature with another 
one, a.k.a. deprecation, is considered a breaking change in the REST 
contract, Approach A would appear to me penalized in that sense, unless 
we agree on more sustainable solutions reflecting a different 
interpretation of Approach A like for example those outlined by Tom (see 
above).

However, I remain more inclined to follow Approach B or C (the latter 
seems more likely ).


Best,

Mario

>
>      Cheers,
>
>      Mario
>
>
>      Il 27/05/2022 16:31, Jasdip Singh ha scritto:
>      > Hi.
>      >
>      > I'd contend that unlike the proposed approach(es), current approach:
>      > - guarantees no collisions under every change scenario (not just optional new field)
>      > - guarantees sufficient transition time for clients when moving to the next version of an extension (without requiring any additional signaling beyond RDAP conformance) and thereby, guarantees near-zero breakage (breakage only possible if a client ignores the transition time)
>      > - has a simple registration model for each opaque extension identifier
>      >
>      > Jasdip
>      >
>      > On 5/27/22, 10:25 AM, "regext on behalf of Gould, James" <[e-mail] on behalf of jgould=[e-mail]> wrote:
>      >
>      >      Mario,
>      >
>      >          [ML] My only objection to Approach C is that every new version would
>      >          result in registering a new extension identifier. I would opt for a less
>      >          verbose solution, if any.
>      >
>      >      I'm not aware of the plan for new versions of the existing extensions, so I don't view it as a scalability issue.  While an extension is an Internet Draft, the pointed versions will not be registered until the draft becomes an RFC.  This is similar to what happens with the EPP extensions, where pre-RFC implementers can use the pointed version contained in the draft for signaling that will eventually become a full registered version (e.g., "0_N" becoming "1" or "1_N" becoming "2") in the registry.  When there are multiple versions of an extension, I believe it is important to capture those versions in the RDAP Extension Registry with a link to the associated specification.  Mixing versioning with the prefixes I believe is unnecessary and brittle, so I don't support Approach A.  Approach B provides the flexibility to define the full RDAP Conformance version in the specification, so it supports versioning without the brittle side effects, but I view Approach C as being better since the versioning is more explicit in the registry.  If there is the risk of an overload of versions in the registry, then I would agree with the concern of Approach C, but I don't believe that risk exists.
>      >
>      >      --
>      >
>      >      JG
>      >
>      >
>      >
>      >      James Gould
>      >      Fellow Engineer
>      >      [e-mail] <applewebdata://13890C55-AAE8-4BF3-A6CE-B4BA42740803/[e-mail]>
>      >
>      >      703-948-3271
>      >      12061 Bluemont Way
>      >      Reston, VA 20190
>      >
>      >      Verisign.com <http://verisigninc.com/>
>      >
>      >      On 5/27/22, 10:10 AM, "Mario Loffredo" <[e-mail]> wrote:
>      >
>      >          Hi james,
>      >
>      >          my comment inline.
>      >
>      >          Il 27/05/2022 14:43, Gould, James ha scritto:
>      >          > Mario,
>      >          >
>      >          > Thank you for providing an example of the complexity of versioning that is associated with tightly coupling the RDAP compliance value with the set of prefixes.  Unfortunately, RDAP doesn't include the same sort of version negotiation that exists in EPP with the use of XML namespace URIs in the greeting and login services.  I view the RDAP Conformance being closer to the EPP greeting services.  I'll continue down the EPP line of discussion, where EPP leverages the XML namespace URIs for versioning that is tied to XML schemas and leverages XML namespace prefixes for grouping of the XML elements.  EPP explicitly requires the use of a namespace-aware XML parser, which enables the use of any XML namespace prefix.  There is no direct tie in the RFCs to the specific XML namespace prefix to use that is linked with the versioned XML namespace URIs.
>      >          [ML] Agreed. I only meant to make WG see things from a different angle
>      >          beyond the considerations based on what RFCs currently permit presenting
>      >          what could be the operational consequences of opting for Approach A.
>      >          >
>      >          >
>      >          > REST and JSON is schema-less, so are we attempting to bring in XML concepts into REST and JSON with the tight coupling of extension RDAP conformance values and the extension elements?
>      >          [ML] Clearly stated that we shouldn't. But what is most important,
>      >          > Approach C that is currently implemented in draft-ietf-regext-rdap-redacted includes the registration of a full versioned identifier for the RDAP Conformance, with "redacted_level_0_3" and the registration of the prefix "redacted" to ensure uniqueness with other extensions.  The "redacted" prefix looks a lot like "redacted_level_0_3", but that is not required.  The tie between the tie is based on the use of the same "Published specification" value in the RDAP Extension Registry.  I haven't heard of a concrete case to help the client out by having the RDAP Conformance value match the prefix with the optional support for versioning in both.  An extension should be additive, and the client would first key off the set of versioned RDAP conformance values, to determine what is supported based on what is defined in the specification.  We have no equivalent of an XML schema, and I don't believe we should attempt to model that in RDAP.
>      >          [ML] Me too.
>      >          > I view attempting to model XML schemas with predefined XML prefixes as brittle and unneeded.
>      >          [ML] Fully agreed. I'd also say "unpractical" as it would reduce the
>      >          benefits from using REST and JSON.
>      >          > Enable true versioning in the RDAP conformance and enable prefixes to be independently registered in the RDAP Extension Registry without any predefined linkage.
>      >
>      >          [ML] My only objection to Approach C is that every new version would
>      >          result in registering a new extension identifier. I would opt for a less
>      >          verbose solution, if any.
>      >
>      >          Summarizing, I'm OK with either approach B or C.
>      >
>      >
>      >          Best,
>      >
>      >          Mario
>      >
>      >          >
>      >          >
>      >          > Thanks,
>      >          >
>      >          --
>      >          Dr. Mario Loffredo
>      >          Technological Unit “Digital Innovation”
>      >          Institute of Informatics and Telematics (IIT)
>      >          National Research Council (CNR)
>      >          via G. Moruzzi 1, I-56124 PISA, Italy
>      >          Phone: [phone]
>      >          Web: http://secure-web.cisco.com/16t5sBrz_iAuxdO4FzKpp7t63WvEdOI56N9ldgS_C5bon4NCc-fivU9_kFZf8_evpDmkcPCcQiuBoJ7ofMrxCHVesyRtQIvx85qEcFV0qX_2PuNNpIb30pT3SRzrneNKg75w7-OAskVaeHoaFH9yk1uOXj-IB65xr1AE0B_z08bGMucXu9VhZ-ghBF2wZjUuw9-C2po2YN2kn9i4nBpQQqX0Kc1A-h2sVt4NJuokO7CbStWfhVUom1hVeNIZuUWn3/http%3A%2F%2Fwww.iit.cnr.it%2Fmario.loffredo
>      >
>      >
>      >      _______________________________________________
>      >      regext mailing list
>      >      [e-mail]
>      >      https://www.ietf.org/mailman/listinfo/regext
>      >
>      > _______________________________________________
>      > regext mailing list
>      > [e-mail]
>      > https://www.ietf.org/mailman/listinfo/regext
>
>      --
>      Dr. Mario Loffredo
>      Technological Unit “Digital Innovation”
>      Institute of Informatics and Telematics (IIT)
>      National Research Council (CNR)
>      via G. Moruzzi 1, I-56124 PISA, Italy
>      Phone: [phone]
>      Web: http://www.iit.cnr.it/mario.loffredo
>
>
-- 
Dr. Mario Loffredo
Technological Unit “Digital Innovation”
Institute of Informatics and Telematics (IIT)
National Research Council (CNR)
via G. Moruzzi 1, I-56124 PISA, Italy
Phone: [phone]
Web: http://www.iit.cnr.it/mario.loffredo