Registration Protocols Extensions                            M. Loffredo
Internet-Draft                                             M. Martinelli
Intended status: Standards Track                     IIT-CNR/Registro.it
Expires: March 5, August 14, 2020                               February 11, 2020                                 September 2, 2019

       Registration Data Access Protocol (RDAP) Partial Response
               draft-ietf-regext-rdap-partial-response-04
               draft-ietf-regext-rdap-partial-response-05

Abstract

   The Registration Data Access Protocol (RDAP) does not include
   capabilities to request partial responses.  In fact, according to the
   user authorization, the server can only return full responses.  A
   partial response capability, especially in the case of search
   queries, could bring benefits to both clients and servers.  This
   document describes an RDAP query extension that allows clients to
   specify their preference for obtaining a partial response.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on March 5, August 14, 2020.

Copyright Notice

   Copyright (c) 2019 2020 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Conventions Used in This Document . . . . . . . . . . . .   3
   2.  Approaches to Partial Response Implementation . . . . . . . .   3
   3.  RDAP Path Segment Specification . . . . . . . . . . . . . . .   5
     3.1.   3
     2.1.  Subsetting Metadata . . . . . . . . . . . . . . . . . . .   5
       3.1.1.   3
       2.1.1.  Representing Subsetting Links . . . . . . . . . . . .   6
   4.   4
   3.  Dealing with Relationships  . . . . . . . . . . . . . . . . .   7
   5.   5
   4.  Basic Field Sets  . . . . . . . . . . . . . . . . . . . . . .   7
   6.   5
   5.  Negative Answers  . . . . . . . . . . . . . . . . . . . . . .   8
   7.   7
   6.  RDAP Conformance  . . . . . . . . . . . . . . . . . . . . . .   9
   8.   8
   7.  Implementation Status . . . . . . . . . . . . . . . . . . . .   9
     8.1.   8
     7.1.  IIT-CNR/Registro.it . . . . . . . . . . . . . . . . . . .   9
   9.   8
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  10
   10.   8
   9.  Security Considerations . . . . . . . . . . . . . . . . . . .  10
   11.   9
   10. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  10
   12.   9
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .  11
     12.1.   9
     11.1.  Normative References . . . . . . . . . . . . . . . . . .  11
     12.2.   9
     11.2.  Informative References . . . . . . . . . . . . . . . . .  11  10
   Appendix A.  Approaches to Partial Response Implementation  . . .  11
     A.1.  Specific Issues Raised by RDAP  . . . . . . . . . . . . .  12
   Appendix B.  Change Log . . . . . . . . . . . . . . . . . . . . .  12  13
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  13  14

1.  Introduction

   The use of partial response in RESTful API ([REST]) design is very
   common.  The rationale is quite simple: instead of returning objects
   in API responses with all data fields, only a subset is returned.
   The benefit is obvious: less data transferred over the network means
   less bandwidth usage, faster server response, less CPU time spent
   both on the server and the client, as well as less memory usage on
   the client.

   Several leading APIs providers (e.g.  LinkedIn [LINKEDIN], Facebook
   [FACEBOOK], Google [GOOGLE]) implement the partial response feature
   by providing an optional query parameter by which users require the
   fields they wish to receive.  Partial response is also considered a
   leading principle by many best practices guidelines in REST APIs
   implementation ([REST-API1], [REST-API2]) in order to improve
   performance, save on bandwidth and possibly accelerate the overall
   interaction.  In other contexts, for example in digital libraries and
   bibliographic catalogues, servers can provide responses according to
   different element sets (i.e. "brief" to get back a short response and
   "full" to get back the complete response)
   Currently, RDAP does not provide a client with any way to request a
   partial response: the server can only provide the client with the
   full response ([RFC7483]).  Furthermore, servers cannot define the
   limits of the results according to partial responses and this causes
   strong inefficiencies.

   The protocol described in this specification extends RDAP search
   capabilities to enable partial responses, responses through the provisioning of
   pre-defined sets of fields the user can request to an RDAP service by
   adding a new query
   parameter and using a RESTful web service. parameter.  The service is implemented using the
   Hypertext Transfer Protocol (HTTP) ([RFC7230]) and the conventions
   described in RFC 7480 ([RFC7480]).

1.1.  Conventions Used in This Document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 ([RFC2119]).

2.  Approaches to Partial Response Implementation

   Looking at the implementation experiences described above, two
   approaches to the implementation  RDAP Path Segment Specification

   The path segment defined in this section is an OPTIONAL extension of partial response can be detected:

   o  the client declares explicitly the data fields to get back;

   o  the client declares
   search path segments defined in RFC 7482 ([RFC7482]).  This document
   defines an RDAP query parameter, "fieldSet", whose value is a name string
   identifying a server pre-defined set of
      data fields.

   The former is more flexible than the latter because clients fields (Figure 1).

   This solution can
   specify all be implemented by the data RDAP providers with less
   effort than fields they need.  However, it selection and easily requested by consumers.  The
   considerations that has some
   drawbacks:

   o  fields have to be declared according led to a given syntax.  This is a
      simple task when the data structure of the object is flat, but it
      is much opt for this solution are reported in
   more difficult when detail in Appendix A.

   https://example.com/rdap/domains?name=example*.com&fieldSet=afieldset

      Figure 1: Example of RDAP search query reporting the object has a tree structure like "fieldSet"
                                 parameter

2.1.  Subsetting Metadata

   According to most advanced principles in REST design, collectively
   known as HATEOAS (Hypermedia as the one Engine of Application State)
   ([HATEOAS]), a JSON object.  The presence of arrays and deep nested
      objects contributes client entering a REST application through an initial
   URI should use the server-provided links to complicate both dynamically discover
   available actions and access the syntax definition resources it needs.  In this way,
   the client is not requested to have prior knowledge of the query service
   and, consequently, to hard code the processing phase on URIs of different resources.
   This would allow the server
      side;

   o  clients should perfectly know the returned data structure to avoid
      cases when make URI changes as the requested fields are invalid;

   o API evolves
   without breaking the request of some fields might not match clients.  Definitively, a REST service should be
   as self-descriptive as possible.

   Therefore, servers implementing the user access levels.
      Clients might put unauthorized fields query parameter described in this
   specification SHOULD provide additional information in their requests and
      servers should define a strategy for providing a response:
      returning always an error response or returning
   responses about the available field sets.  Such information is
   collected in a response that
      ignores new data structure named "subsetting_metadata"
   containing the unauthorized fields.

   In addition to those listed above, RDAP responses raise some specific
   issues: following properties:

   o  most of  "currentFieldSet": "String" (REQUIRED) either the relevant information value of the entity object is included
      "fieldSet" parameter as specified in the jCard but such information cannot be easily selected
      because it is split into query string or the items of a jagged array; field
      set applied by default;

   o  RDAP responses contain some properties providing service
      information (e.g. rdapConformance, links, notices, remarks, etc.)
      which are not normally selected but they are just as important.
      They could be returned anyway but, in this case, the server would
      provide unrequested data.

   As  "availableFieldSets": "AvailableFieldSet[]" (OPTIONAL) an example compliant to array of
      objects each one describing an alternate available field set.
      Members are:

      *  "name": "String" (REQUIRED) the first approach, field set name;
      *  "default": "Boolean" (REQUIRED) whether the Catnap Query
   Language ([CQL]) field set is
         applied by default;
      *  "description": "String" (OPTIONAL) a comprehensive expression language that can be
   used to customize the JSON response of a RESTful web service.  The
   practical application human-readable description
         of CQL to RDAP responses points out that
   declaring explicitly the output fields would still be acceptable when
   a few fields are requested but it would become very complicated if
   the fields should be more.  In the following, two CQL expressions for
   a search domain query are shown (Figure 1): field set;
      *  "links": "Link[]" (OPTIONAL) an array of links as described in
         RFC 8288 ([RFC8288]) containing the first, only
   objectClassName and ldhName are requested, in query string that applies
         the second, field set.

2.1.1.  Representing Subsetting Links

   An RDAP server MAY use the fields
   of a possible WHOIS-like response are listed.

https://example.com/rdap/domains?name=example*.com
        &fields=domainSearchResults(objectClassName,ldhName)

https://example.com/rdap/domains?name=example*.com
        &fields=domainSearchResults(objectClassName,ldhName,unicodeName,
                status,
                events(eventAction,eventDate),
                entities(objectClassName,handle,roles),
                nameservers(objectClassName,ldhName))

      Figure 1: Examples "links" array of CQL expressions for a search domain query

   The latter approach seems the "subsetting_metadata"
   element to facilitate RDAP interoperability.  In
   fact, servers can define some basic provide ready-made references ([RFC8288]) to the available
   field sets which, if known (Figure 2).  Each link represents a reference to an
   alternate view of the
   clients, results.

   {
     "rdapConformance": [
       "rdap_level_0",
       "subsetting_level_0"
     ],
     ...
     "subsetting_metadata": {
        "currentFieldSet": "afieldset",
        "availableFieldSets": [
        {
        "name": "anotherfieldset",
        "description": "Contains some fields",
        "default": false,
        "links": [
           {
           "value": "https://example.com/rdap/domains?name=*nr.com
                     &fieldSet=afieldset",
           "rel": "alternate",
           "href": "https://example.com/rdap/domains?name=*nr.com
                    &fieldSet=anotherfieldset",
           "title": "Result Subset Link",
           "type": "application/rdap+json"
           },
           ...
        ]
     },
     "domainSearchResults": [
       ...
     ]
   }

           Figure 2: Example of a "subsetting_metadata" instance

3.  Dealing with Relationships

   Some additional considerations can increase the probability to get be made about how second level
   objects could be represented within a valid response.  The
   usage of field sets lets the query string be less complex. set.  In
   addition, fact, since the definition of pre-defined sets of fields makes easier
   topmost objects could be returned according to establish different field sets,
   the results limits.

   Finally, considering that there is not a real need same thing could go for RDAP users to
   have the maximum flexibility in defining all their related objects.  As a consequence,
   the possible sets of
   logically connected fields (e.g. users interested response could contain either no relationship or associated
   objects which are in domains usually
   need turn provided according to know the status, a field set.

4.  Basic Field Sets

   In order to improve interoperability between clients and servers, the creation date,
   name, as well as the expiry date list of fields for each
   domain), the latter approach is preferred.

3. field set, should be
   shared by most of RDAP Path Segment Specification

   The path segment defined in this providers.  This section defines three basic
   field sets which servers MAY implement to facilitate their
   interaction with clients:

   o  "id": the server provides only the key field, respectively:
      "handle" for entities, "ldhName" for domains and nameservers.  If
      a returned domain or nameserver is an OPTIONAL extension of
   search path segments defined IDN ([RFC5890]), then the
      "unicodeName" field MUST be included in RFC 7482 ([RFC7482]). the response.  This document
   defines an RDAP query parameter, "fieldSet", whose value is a string
   identifying a server pre-defined field
      set could be used when the client wants to simply obtain a
      collection of fields object identifiers (Figure 2).

   https://example.com/rdap/domains?name=example*.com&fieldSet=afieldset

      Figure 2: Example of RDAP search query reporting 3);

   o  "brief": it contains the "fieldSet"
                                 parameter

3.1.  Subsetting Metadata

   According to most advanced principles fields that can be included in REST design, collectively
   known as HATEOAS (Hypermedia as the Engine of Application State)
   ([HATEOAS]), a "short"
      response.  This field set could be used when the client entering is asking
      for a REST application through an initial
   URI should use the server-provided links to dynamically discover
   available actions and access subset of the resources full response which gives a basic knowledge of
      each object;

   o  "full": it needs.  In this way, contains all the client information the server can provide for
      a particular object.

   The "objectClassName" field is not requested to have prior knowledge implicitly included in each of the service
   and, consequently,
   above field sets.  RDAP providers are RECOMMENDED to include a "self"
   link in each field set other than "full" in order to hard code the URIs of different resources.
   This would allow the server clients to make URI changes as
   easily request for the API evolves
   without breaking the clients.  Definitively, a REST service should be
   as self-descriptive as possible.

   Therefore, servers implementing the query parameter described in this
   specification SHOULD provide additional information in their
   responses about the available field sets.  Such information is
   collected in a new data structure named "subsetting_metadata"
   containing the following properties:

   o  "currentFieldSet": "String" (REQUIRED) either the value of
      "fieldSet" parameter as specified in the query string or the field
      set applied by default;

   o  "availableFieldSets": "AvailableFieldSet[]" (OPTIONAL) an array of
      objects each one describing an alternate available field set.
      Members are:

      *  "name": "String" (REQUIRED) the field set name;
      *  "default": "Boolean" (REQUIRED) whether the field set is
         applied by default;
      *  "description": "String" (OPTIONAL) a human-readable description
         of the field set;

      *  "links": "Link[]" (OPTIONAL) an array of links as described in
         RFC 8288 ([RFC8288]) containing the query string that applies
         the field set.

3.1.1.  Representing Subsetting Links

   An full objects.  RDAP server providers MAY use the "links" array of the "subsetting_metadata"
   element to provide ready-made references ([RFC8288]) to the available also add any
   property providing service information.

   Fields included in "brief" and "full" field sets (Figure 3).  Each link represents a reference could be returned
   according to an
   alternate view of the results. user access levels.

   {
     "rdapConformance": [
           "rdap_level_0",
       "subsetting_level_0"
     ],
     ...
     "subsetting_metadata":
     "domainSearchResults": [
       {
        "currentFieldSet": "afieldset",
        "availableFieldSets":
         "objectClassName": "domain",
         "ldhName": "example1.com",
         "links": [
           {
        "name": "anotherfieldset",
        "description": "Contains some fields",
        "default": false,
           "value": "https://example.com/rdap/domain/example1.com",
           "rel": "self",
           "href": "https://example.com/rdap/domain/example1.com",
           "type": "application/rdap+json"
           }
         ],
       },
       {
         "objectClassName": "domain",
         "ldhName": "example2.com",
         "links": [
           {
           "value": "https://example.com/rdap/domains?name=*nr.com
                     &fieldSet=afieldset", "https://example.com/rdap/domain/example2.com",
           "rel": "alternate", "self",
           "href": "https://example.com/rdap/domains?name=*nr.com
                    &fieldSet=anotherfieldset",
           "title": "Result Subset Link", "https://example.com/rdap/domain/example2.com",
           "type": "application/rdap+json"
           }
         ],
       },
       ...
     ]
     },
     "domainSearchResults": [
       ...
     ]
   }

    Figure 3: Example of a "subsetting_metadata" instance

4.  Dealing with Relationships

   Some additional considerations can be made about how second level
   objects could be represented within a field set.  In fact, since the
   topmost objects could be returned RDAP response according to different field sets, the same thing could go for their related objects.  As a consequence, "id" field set

5.  Negative Answers

   Each request including an unsupported field set SHOULD obtain an HTTP
   400 (Bad Request) response code.

   Optionally, the response could contain either no relationship or associated
   objects which are MAY include additional information regarding
   the negative answer in turn provided according to a field set.

5.  Basic Field Sets

   In order to improve interoperability between clients the HTTP entity body.

6.  RDAP Conformance

   Servers returning the "subsetting_metadata" section in their
   responses MUST include "subsetting_level_0" in the rdapConformance
   array.

7.  Implementation Status

   NOTE: Please remove this section and servers, the
   name, as well reference to RFC 7942 prior
   to publication as an RFC.

   This section records the list status of fields for each field set, should be
   shared by most known implementations of RDAP providers.  This section defines three basic
   field sets which servers MAY implement to facilitate their
   interaction with clients:

   o  "id": the server provides only
   protocol defined by this specification at the key field, respectively:
      "handle" for entities, "ldhName" for domains time of posting of this
   Internet-Draft, and nameservers.  If is based on a returned domain or nameserver proposal described in RFC 7942
   ([RFC7942]).  The description of implementations in this section is an IDN ([RFC5890]), then
   intended to assist the
      "unicodeName" field MUST be included IETF in the response.  This field
      set could be used when the client wants its decision processes in progressing
   drafts to simply obtain a
      collection of object identifiers (Figure 4);

   o  "brief": it contains the fields RFCs.  Please note that can be included in a "short"
      response.  This field set could be used when the client is asking
      for a subset listing of any individual
   implementation here does not imply endorsement by the full response which gives a basic knowledge of
      each object;

   o  "full": it contains all IETF.
   Furthermore, no effort has been spent to verify the information the server can provide for
      a particular object.

   The "objectClassName" field
   presented here that was supplied by IETF contributors.  This is implicitly included in each not
   intended as, and must not be construed to be, a catalog of the
   above field sets.  RDAP providers available
   implementations or their features.  Readers are RECOMMENDED advised to include a "self"
   link in each field set note that
   other than "full" in order implementations may exist.

   According to RFC 7942, "this will allow clients reviewers and working groups
   to
   easily request for assign due consideration to documents that have the full objects.  RDAP providers MAY also add any
   property providing service information.

   Fields included in "brief" benefit of
   running code, which may serve as evidence of valuable experimentation
   and "full" field sets could be returned
   according feedback that have made the implemented protocols more mature.
   It is up to the user access levels.

   {
     "rdapConformance": [
           "rdap_level_0",
     ],
     ...
     "domainSearchResults": [
       {
         "objectClassName": "domain",
         "ldhName": "example1.com",
         "links": [
           {
           "value": "https://example.com/rdap/domain/example1.com",
           "rel": "self",
           "href": "https://example.com/rdap/domain/example1.com",
           "type": "application/rdap+json"
           }
         ],
       },
       {
         "objectClassName": "domain",
         "ldhName": "example2.com",
         "links": [
           {
           "value": "https://example.com/rdap/domain/example2.com",
           "rel": "self",
           "href": "https://example.com/rdap/domain/example2.com",
           "type": "application/rdap+json"
           }
         ],
       },
       ...
     ]
   }

    Figure 4: Example individual working groups to use this information as
   they see fit".

7.1.  IIT-CNR/Registro.it

      Responsible Organization: Institute of Informatics and Telematics
      of National Research Council (IIT-CNR)/Registro.it
      Location: https://rdap.pubtest.nic.it/
      Description: This implementation includes support for RDAP response according queries
      using data from .it public test environment.
      Level of Maturity: This is an "alpha" test implementation.
      Coverage: This implementation includes all of the features
      described in this specification.
      Contact Information: Mario Loffredo, mario.loffredo@iit.cnr.it

8.  IANA Considerations

   IANA is requested to register the "id" field set

6.  Negative Answers

   Each request including an unsupported field set SHOULD obtain an HTTP
   400 (Bad Request) following value in the RDAP
   Extensions Registry:

      Extension identifier: subsetting
      Registry operator: Any
      Published specification: This document.
      Contact: IESG <iesg@ietf.org>
      Intended usage: This extension describes a best practice for
      partial response code.

   Optionally, provisioning.

9.  Security Considerations

   The search query typically requires more server resources (such as
   memory, CPU cycles, and network bandwidth) when compared to the
   lookup query.  This increases the risk of server resource exhaustion
   and subsequent denial of service due to abuse.  Partial response MAY include additional information regarding can
   contribute together with other strategies (e.g. restricting search
   functionality, limiting the negative answer in rate of search requests, truncating and
   paging results) to mitigate this risk.

   Furthermore, partial response can support RDAP operators to implement
   a versatile access control policy through the HTTP entity body.

7. authentication
   mechanisms as described in RFC 7481 ([RFC7481]).  In fact, RDAP Conformance

   Servers returning
   operators can follow different, not alternative, approaches to the "subsetting_metadata" section in their
   building of responses MUST include "subsetting_level_0" according to the user access levels:

   o  the list of fields for each set can be different according to the
      user access levels;

   o  some field sets could be available only to some users.

   Servers can also define different results limits according to the
   available field sets, so a more flexible truncation strategy can be
   realized.

   Therefore, the new query parameter presented in this document
   provides the RDAP operators with a way to implement a secure server
   without penalizing its efficiency.

10.  Acknowledgements

   The authors would like to acknowledge Scott Hollenbeck, Tom Harrison
   and Karl Heinz Wolf for their contribution to this document.

11.  References

11.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC5890]  Klensin, J., "Internationalized Domain Names for
              Applications (IDNA): Definitions and Document Framework",
              RFC 5890, DOI 10.17487/RFC5890, August 2010,
              <https://www.rfc-editor.org/info/rfc5890>.

   [RFC7230]  Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
              Protocol (HTTP/1.1): Message Syntax and Routing",
              RFC 7230, DOI 10.17487/RFC7230, June 2014,
              <https://www.rfc-editor.org/info/rfc7230>.

   [RFC7480]  Newton, A., Ellacott, B., and N. Kong, "HTTP Usage in the
              Registration Data Access Protocol (RDAP)", RFC 7480,
              DOI 10.17487/RFC7480, March 2015,
              <https://www.rfc-editor.org/info/rfc7480>.

   [RFC7481]  Hollenbeck, S. and N. Kong, "Security Services for the
              Registration Data Access Protocol (RDAP)", RFC 7481,
              DOI 10.17487/RFC7481, March 2015,
              <https://www.rfc-editor.org/info/rfc7481>.

   [RFC7482]  Newton, A. and S. Hollenbeck, "Registration Data Access
              Protocol (RDAP) Query Format", RFC 7482,
              DOI 10.17487/RFC7482, March 2015,
              <https://www.rfc-editor.org/info/rfc7482>.

   [RFC7483]  Newton, A. and S. Hollenbeck, "JSON Responses for the
              Registration Data Access Protocol (RDAP)", RFC 7483,
              DOI 10.17487/RFC7483, March 2015,
              <https://www.rfc-editor.org/info/rfc7483>.

   [RFC8288]  Nottingham, M., "Web Linking", RFC 8288,
              DOI 10.17487/RFC8288, October 2017,
              <https://www.rfc-editor.org/info/rfc8288>.

11.2.  Informative References

   [CQL]      Whitaker, G., "Catnap Query Language Reference", September
              2017, <https://github.com/gregwhitaker/catnap/wiki/Catnap-
              Query-Language-Reference>.

   [FACEBOOK]
              facebook.com, "facebook for developers - Using the Graph
              API", July 2017, <https://developers.facebook.com/docs/
              graph-api/using-graph-api>.

   [GOOGLE]   google.com, "Making APIs Faster: Introducing Partial
              Response and Partial Update", March 2010,
              <http://googlecode.blogspot.it/2010/03/making-apis-faster-
              introducing-partial.html>.

   [HATEOAS]  Jedrzejewski, B., "HATEOAS - a simple explanation", 2018,
              <https://www.e4developer.com/2018/02/16/hateoas-simple-
              explanation/>.

   [LINKEDIN]
              linkedin.com, "Java One 2009: Building Consistent RESTful
              APIs in a High Performance Environment", July 2009,
              <https://blog.linkedin.com/2009/07/08/brandon-duncan-java-
              one-building-consistent-restful-apis-in-a-high-
              performance-environment>.

   [REST]     Fielding, R., "Architectural Styles and the rdapConformance
   array.

8. Design of
              Network-based Software Architectures", 2000,
              <http://www.restapitutorial.com/media/
              RESTful_Best_Practices-v1_1.pdf>.

   [REST-API1]
              Jobinesh, P., "RESTful Java Web Services - Second
              Edition", September 2015.

   [REST-API2]
              Masse, M., "REST API Design Rulebook", October 2011.

   [RFC7942]  Sheffer, Y. and A. Farrel, "Improving Awareness of Running
              Code: The Implementation Status

   NOTE: Please remove this section and the reference to Section", BCP 205,
              RFC 7942 prior 7942, DOI 10.17487/RFC7942, July 2016,
              <https://www.rfc-editor.org/info/rfc7942>.

Appendix A.  Approaches to publication as an RFC.

   This section records the status of known implementations of the
   protocol defined by this specification Partial Response Implementation

   Looking at the time of posting of this
   Internet-Draft, and is based on a proposal implementation experiences described in RFC 7942
   ([RFC7942]).  The description of implementations in this section is
   intended to assist the IETF in its decision processes in progressing
   drafts Section 1, two
   approaches to RFCs.  Please note that the listing of any individual implementation here does not imply endorsement by of partial response can be detected:

   o  the IETF.
   Furthermore, no effort has been spent to verify client declares explicitly the information
   presented here that was supplied by IETF contributors.  This is not
   intended as, and must not be construed to be, a catalog of available
   implementations or their features.  Readers are advised to note that
   other implementations may exist.

   According to RFC 7942, "this will allow reviewers and working groups
   to assign due consideration data fields to documents that have get back;

   o  the benefit of
   running code, which may serve as evidence client declares a name identifying a server pre-defined set of valuable experimentation
   and feedback that have made the implemented protocols more mature.
   It
      data fields.

   The former is up to more flexible than the individual working groups to use this information as latter because clients can
   specify all the data fields they see fit".

8.1.  IIT-CNR/Registro.it

      Responsible Organization: Institute of Informatics and Telematics
      of National Research Council (IIT-CNR)/Registro.it
      Location: https://rdap.pubtest.nic.it/
      Description: need.  However, it has some
   drawbacks:

   o  fields have to be declared according to a given syntax.  This implementation includes support for RDAP queries
      using is a
      simple task when the data from .it public test environment.
      Level structure of Maturity: This the object is flat, but it
      is much more difficult when the object has a "proof tree structure like
      the one of concept" research
      implementation.
      Coverage: This implementation includes all a JSON object.  The presence of arrays and deep nested
      objects contributes to complicate both the features
      described in this specification.
      Contact Information: Mario Loffredo, mario.loffredo@iit.cnr.it

9.  IANA Considerations

   IANA is requested syntax definition of
      the query and, consequently, the processing phase on the server
      side;

   o  clients should perfectly know the returned data structure to register avoid
      cases when the following value in requested fields are invalid;

   o  the RDAP
   Extensions Registry:

      Extension identifier: subsetting
      Registry operator: Any
      Published specification: This document.
      Contact: IESG <iesg@ietf.org>
      Intended usage: This extension describes request of some fields might not match the user access levels.
      Clients might put unauthorized fields in their requests and
      servers should define a strategy for providing a response:
      returning always an error response or returning a best practice for
      partial response provisioning.

10.  Security Considerations

   The search query typically requires more server resources (such as
   memory, CPU cycles, and network bandwidth) when compared to that
      ignores the
   lookup query.  This increases unauthorized fields.

A.1.  Specific Issues Raised by RDAP

   In addition to those listed above, RDAP responses raise some specific
   issues:

   o  most of the risk relevant information of server resource exhaustion
   and subsequent denial the entity object is included
      in the jCard but such information cannot be easily selected
      because it is split into the items of a jagged array;

   o  RDAP responses contain some properties providing service due
      information (e.g. rdapConformance, links, notices, remarks, etc.)
      which are not normally selected but they are just as important.
      They could be returned anyway but, in this case, the server would
      provide unrequested data.

   As an example compliant to abuse.  Partial response the first approach, the Catnap Query
   Language ([CQL]) is a comprehensive expression language that can
   contribute together with other strategies (e.g. restricting search
   functionality, limiting be
   used to customize the rate JSON response of search requests, truncating and
   paging results) a RESTful web service.  The
   practical application of CQL to mitigate this risk.

   Furthermore, partial response can support RDAP operators to implement responses points out that
   declaring explicitly the output fields would still be acceptable when
   a versatile access control policy through few fields are requested but it would become very complicated if
   the HTTP authentication
   mechanisms as described in RFC 7481 ([RFC7481]). fields should be more.  In fact, RDAP
   operators can follow different, not alternative, approaches to the
   building of responses according to following, two CQL expressions for
   a search domain query are shown (Figure 4): in the first, only
   objectClassName and ldhName are requested, in the user access levels:

   o second, the list of fields
   of a possible WHOIS-like response are listed.

https://example.com/rdap/domains?name=example*.com
        &fields=domainSearchResults(objectClassName,ldhName)

https://example.com/rdap/domains?name=example*.com
        &fields=domainSearchResults(objectClassName,ldhName,unicodeName,
                status,
                events(eventAction,eventDate),
                entities(objectClassName,handle,roles),
                nameservers(objectClassName,ldhName))

      Figure 4: Examples of CQL expressions for each set can be different according a search domain query

   The latter approach seems to the
      user access levels;

   o facilitate RDAP interoperability.  In
   fact, servers can define some basic field sets could be available only to some users.

   Servers can also define different results limits according which, if known to the
   available field sets, so a more flexible truncation strategy
   clients, can be
   realized.

   Therefore, the new query parameter presented in this document
   provides increase the RDAP operators with a way probability to implement get a secure server
   without penalizing its efficiency.

11.  Acknowledgements valid response.  The authors would like to acknowledge Scott Hollenbeck and Tom
   Harrison for their contribution to this document.

12.  References

12.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC5890]  Klensin, J., "Internationalized Domain Names for
              Applications (IDNA): Definitions and Document Framework",
              RFC 5890, DOI 10.17487/RFC5890, August 2010,
              <https://www.rfc-editor.org/info/rfc5890>.

   [RFC7230]  Fielding, R., Ed. and J. Reschke, Ed., "Hypertext Transfer
              Protocol (HTTP/1.1): Message Syntax and Routing",
              RFC 7230, DOI 10.17487/RFC7230, June 2014,
              <https://www.rfc-editor.org/info/rfc7230>.

   [RFC7480]  Newton, A., Ellacott, B., and N. Kong, "HTTP Usage in
   usage of field sets lets the
              Registration Data Access Protocol (RDAP)", RFC 7480,
              DOI 10.17487/RFC7480, March 2015,
              <https://www.rfc-editor.org/info/rfc7480>.

   [RFC7481]  Hollenbeck, S. and N. Kong, "Security Services for query string be less complex.  In
   addition, the
              Registration Data Access Protocol (RDAP)", RFC 7481,
              DOI 10.17487/RFC7481, March 2015,
              <https://www.rfc-editor.org/info/rfc7481>.

   [RFC7482]  Newton, A. and S. Hollenbeck, "Registration Data Access
              Protocol (RDAP) Query Format", RFC 7482,
              DOI 10.17487/RFC7482, March 2015,
              <https://www.rfc-editor.org/info/rfc7482>.

   [RFC7483]  Newton, A. and S. Hollenbeck, "JSON Responses for definition of pre-defined sets of fields makes easier
   to establish the
              Registration Data Access Protocol (RDAP)", RFC 7483,
              DOI 10.17487/RFC7483, March 2015,
              <https://www.rfc-editor.org/info/rfc7483>.

   [RFC8288]  Nottingham, M., "Web Linking", RFC 8288,
              DOI 10.17487/RFC8288, October 2017,
              <https://www.rfc-editor.org/info/rfc8288>.

12.2.  Informative References

   [CQL]      Whitaker, G., "Catnap Query Language Reference", September
              2017, <https://github.com/gregwhitaker/catnap/wiki/
              Catnap-Query-Language-Reference>.

   [FACEBOOK]
              facebook.com, "facebook results limits.

   Finally, considering that there is not a real need for developers - Using RDAP users to
   have the Graph
              API", July 2017, <https://developers.facebook.com/docs/
              graph-api/using-graph-api>.

   [GOOGLE]   google.com, "Making APIs Faster: Introducing Partial
              Response and Partial Update", March 2010,
              <http://googlecode.blogspot.it/2010/03/
              making-apis-faster-introducing-partial.html>.

   [HATEOAS]  Jedrzejewski, B., "HATEOAS - a simple explanation", 2018,
              <https://www.e4developer.com/2018/02/16/
              hateoas-simple-explanation/>.

   [LINKEDIN]
              linkedin.com, "Java One 2009: Building Consistent RESTful
              APIs maximum flexibility in a High Performance Environment", July 2009,
              <https://blog.linkedin.com/2009/07/08/brandon-duncan-java-
              one-building-consistent-restful-apis-in-a-high-
              performance-environment>.

   [REST]     Fielding, R., "Architectural Styles and defining all the Design possible sets of
              Network-based Software Architectures", 2000,
              <http://www.restapitutorial.com/media/
              RESTful_Best_Practices-v1_1.pdf>.

   [REST-API1]
              Jobinesh, P., "RESTful Java Web Services - Second
              Edition", September 2015.

   [REST-API2]
              Masse, M., "REST API Design Rulebook", October 2011.

   [RFC7942]  Sheffer, Y. and A. Farrel, "Improving Awareness
   logically connected fields (e.g. users interested in domains usually
   need to know the status, the creation date, the expiry date of Running
              Code: The Implementation Status Section", BCP 205,
              RFC 7942, DOI 10.17487/RFC7942, July 2016,
              <https://www.rfc-editor.org/info/rfc7942>. each
   domain), the latter approach is preferred.

Appendix A. B.  Change Log

   00:  Initial working group version ported from draft-loffredo-regext-
      rdap-partial-response-03
   01:  Removed "FOR DISCUSSION" items.  Changed the basic field sets
      from REQUIRED to OPTIONAL.  Removed the definition of fields
      included in "brief" field set.  Provided a more detailed
      description of "subsetting_metadata" structure.  Removed some
      references.
   02:  Added the "Negative Answers" section.  Changed "IANA
      Considerations" section.
   03:  Added the "unicodeName" field in the id fieldSet when a returned
      domain or nameserver is an IDN.  Added RFC5890 to "Normative
      References" section.
   04:  Recommended the RDAP providers to include a "self" link in any
      field set other than "full".  Updated "Acknowledgements" section.
   05:  Moved "Approaches to Partial Response Implementation" section to
      the appendix.

Authors' Addresses

   Mario Loffredo
   IIT-CNR/Registro.it
   Via Moruzzi,1
   Pisa  56124
   IT

   Email: mario.loffredo@iit.cnr.it
   URI:   http://www.iit.cnr.it

   Maurizio Martinelli
   IIT-CNR/Registro.it
   Via Moruzzi,1
   Pisa  56124
   IT

   Email: maurizio.martinelli@iit.cnr.it
   URI:   http://www.iit.cnr.it