[regext] Benjamin Kaduk's Discuss on draft-ietf-regext-rdap-sorting-and-paging-17: (with DISCUSS and COMMENT)

[Benjamin Kaduk via Datatracker <[e-mail]>]

Benjamin Kaduk has entered the following ballot position for
draft-ietf-regext-rdap-sorting-and-paging-17: Discuss

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DISCUSS:
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Should we say something about which order the sorting criteria are
applied (first to last vs last to first) when multiple sortItems are
specified in a query?

I recognize that in the HATEOS model, the actual JSONPaths reported by
the server should be used by the client to determine what a given sort
property does, but it also seems like it would be confusing for this
document to specify (e.g.) an "email" property with specific JSONPath,
and then have a server go off and use "email" to mean something else,
even if that is just the addition of "pref" as discussed at the end of
Section 2.3.1.  Do we want to try to have the properties defined by this
document be universally defined and encourage the use of new/different
property names for variations on them?  (The answer may well be "no",
but the answer is not intuitively clear to me.)  To put it another way,
is the list in Section 2.3.1 normative, or just an example?


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COMMENT:
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Section 1

   However, there are some drawbacks associated with the use of the HTTP
   header.  First, the header properties cannot be set directly from a
   web browser.  Moreover, in an HTTP session, the information on the
   status (i.e. the session identifier) is usually inserted in the
   header or a cookie, while the information on the resource
   identification or the search type is included in the query string.
   The second approach is therefore not compliant with the HTTP standard
   [RFC7230].  As a result, this document describes a specification
   based on the use of query parameters.

A few more words (section number from 7230?) on why the second approach
is not compliant with HTTP might help the reader, though it isn't
stricly necessary (we're not using it, after all).

Section 2.1

      *  "jsonPath": "String" (OPTIONAL) the JSONPath of the RDAP field
         corresponding to the property;

What is this path relative to?  (Does the client have to know from the
other context what type of object it refers to?)

      *  "links": "Link[]" (OPTIONAL) an array of links as described in
         [RFC8288] containing the query string that applies the sort
         criterion.

Just to check: this is going to have the same structure for a Link
object that draft-ietf-regext-rdap-partial-response does?  (I am not
coming up with a great way to deduplicate the definitions, off the top
of my head.)

   o  "pageSize": "Numeric" (OPTIONAL) a numeric value representing the
      number of objects returned in the current page.  It MUST be
      provided if and only if the total number of objects exceeds the
      page size.  This property is redundant for RDAP clients because
      the page size can be derived from the length of the search results
      array but, it can be helpful if the end user interacts with the
      server through a web browser;

If it's redundant, we should probably say something about error handling
for when the things that are supposed to be identical have different
values.

Section 2.3

   Except for sorting IP addresses, servers MUST implement sorting
   according to the JSON value type of the RDAP field the sorting
   property refers to.  That is, JSON strings MUST be sorted
   lexicographically and JSON numbers MUST be sorted numerically.  If IP
   addresses are represented as JSON strings, they MUST be sorted based
   on their numeric conversion.

There are more JSON types than string and number; are those other types
garanteed to not appear in sortable RDAP fields?  (I can't see how such
a guarantee could be made, given that servers can define their own
sorting properties.)

   If the "sort" parameter reports an allowed sorting property, it MUST
   be provided in the "currentSort" field of the "sorting_metadata"
   element.

nit: is "reports" the best word to describe this behavior (which, IIUC,
is "present in the query component of the request URL"?

Section 2.3.1

   In the "sort" parameter ABNF syntax, property-ref represents a
   reference to a property of an RDAP object.  Such a reference could be
   expressed by using a JSONPath.  The JSONPath in a JSON document

nit: is there a missing word here ("a JSONPath expression")?

   o  Note that some of the object specific properties are also defined
      as query paths.  The object specific properties include:

nit: the list structure in this item does not seem parallel to the
structure of the first item.

      as two representations of the same value.  By default, the
      unicodeName value MUST be used while sorting.  When the
      unicodeName is unavailable, the value of the ldhName MUST be used
      instead;

I'm not entirely sure how much value "by default" adds here.  Would the
meaning be different if we said "The unicodeName value MUST be used
while sorting if it is present; when the unicodeName is unavailable, the
value of the ldhName is used instead"?

   o  The jCard "sort-as" parameter MUST be ignored for the sorting
      capability described in this document;

It's a little bit of a juxtaposition to refer to jCard here in the prose
but vcard in the table.

   o  Even if a nameserver can have multiple IPv4 and IPv6 addresses,
      the most common configuration includes one address for each IP
      version.  Therefore, the assumption of having a single IPv4 and/or
      IPv6 value for a nameserver cannot be considered too stringent.

I disagree with the flat assertion that it "cannot be considered too
stringent".  It can be so considered, as a matter of difference of
opinion; what is appropriate to do here is to say that this
document/protocol makes the assumption (especially since we go on to
describe the exception-handling procedure when the assumption is
violated).

   o  Multiple events with a given action on an object might be
      returned.  If this occurs, sorting MUST be applied to the most
      recent event;

This makes a lot of sense as the default and I don't propose changing it
now, but I do wonder how hard it would be to add support later for
sorting on (say) the oldest event instead.

   The "jsonPath" field in the "sorting_metadata" element is used to
   clarify the RDAP field the sorting property refers to.  The mapping
   between the sorting properties and the JSONPaths of the RDAP fields
   is shown below:
   [...]
      name

         $.domainSearchResults[*].unicodeName

This seems to ignore the subtlety regarding unicodeName vs ldhName.  Is
there a way it could be expressed in JSONPath?

   o  Nameserver

      name

         $.domainSearchResults[*].unicodeName

Presumably this is supposed to be nameserverSearchResults?

Section 2.4

I think we want another introductory paragraph like:

% The cursor parameter is used by the server to preserve information
% about the pagination state of a given query's results across calls to
% the search API, so that successive requests by the client can return
% page N, N+1, N+2, etc.  Its value is only required to be interpretable
% by the server and could be implemented, for example, as an opaque
% database lookup key.  If a server does use a method for generating
% cursor values that involves internal structure, such as the one
% described below, the server needs to recognize that the value supplied
% by a client could have been modified (maliciously), and implement
% appropriate bounds-checking and similar measures when parsing received
% values.

The current wording strongly suggests that base64-encoding a meaningful
value that the client could inspect or even construct is required, and I
do not think that is very maintainable or what was intended, given the
current second paragraph ("servers can change the method over time
without announcing anything to clients").

(side note) I'm also pretty partial to the way JMAP discusses returning
(paginated, but non-uniformly) changes to a given data stream, e.g., at
https://www.rfc-editor.org/rfc/rfc8620.html#section-5.2 -- any given
state is named, and you can get "stuff starting at <named state>" and
the name to use for the state as of the current reply.

Section 4

If the server doesn't have access to an efficient (e.g.) counting
operation on the backend, would we recommend that the server not support
sorting/pagination, since there's not much benefit from having the
server pull up all the results and count them just to be able to return
the total count value back to the client, and then go do the same work again
when the client asks for the next page of results?

Section 7

I suggest noting that (encoded) structured "cursor" values present a new
attack surface on the server that needs to be protected.

   results in a response.  However, this last security policy can result
   in a higher inefficiency if the RDAP server does not provide any
   functionality to return the truncated results.

I'm not sure I understand (or agree with) this last sentence -- it seems
that unlateral silent truncation of results by the server leads to not
just inefficiency but also potential security considerations in its own
right, with the client not knowing that it has incomplete results.
Also, if the server is truncating the results, by definition it "has
functionality to return the truncated results" -- that's what it's
doing!  So I assume the intent was to say something about negotiating or
indicating that the results are truncated, not actually doing the
truncation.

   The new parameters presented in this document provide RDAP operators
   with a way to implement a server that reduces inefficiency risks.

[same question about "inefficiency" being the right word]

Appendix B

   o  It does not allow direct navigation to arbitrary pages because the
      result set must be scrolled in sequential order starting from the
      initial page;

(side note) I didn't follow the references, so maybe this was covered
there, but I don't quite follow why direct navigation is impossible.  If
you use a key field for seeking, can't you just start in the middle from
some known value for that key field?

Appendix C.2

   total count.  Therefore, as "totalCount" is an optional response
   information, fetching always the total number of rows has been

I'm not entirely sure in what sense "optional response information" is
intended -- my reading of Section 2.1 is that it's mandatory to return
totalCount if the client included the 'count' query parameter.