draft-ietf-regext-rdap-partial-response-04.txt   draft-ietf-regext-rdap-partial-response-05.txt 
Registration Protocols Extensions M. Loffredo Registration Protocols Extensions M. Loffredo
Internet-Draft M. Martinelli Internet-Draft M. Martinelli
Intended status: Standards Track IIT-CNR/Registro.it Intended status: Standards Track IIT-CNR/Registro.it
Expires: March 5, 2020 September 2, 2019 Expires: August 14, 2020 February 11, 2020
Registration Data Access Protocol (RDAP) Partial Response Registration Data Access Protocol (RDAP) Partial Response
draft-ietf-regext-rdap-partial-response-04 draft-ietf-regext-rdap-partial-response-05
Abstract Abstract
The Registration Data Access Protocol (RDAP) does not include The Registration Data Access Protocol (RDAP) does not include
capabilities to request partial responses. In fact, according to the capabilities to request partial responses. In fact, according to the
user authorization, the server can only return full responses. A user authorization, the server can only return full responses. A
partial response capability, especially in the case of search partial response capability, especially in the case of search
queries, could bring benefits to both clients and servers. This queries, could bring benefits to both clients and servers. This
document describes an RDAP query extension that allows clients to document describes an RDAP query extension that allows clients to
specify their preference for obtaining a partial response. specify their preference for obtaining a partial response.
skipping to change at page 1, line 36 skipping to change at page 1, line 36
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/. Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on March 5, 2020. This Internet-Draft will expire on August 14, 2020.
Copyright Notice Copyright Notice
Copyright (c) 2019 IETF Trust and the persons identified as the Copyright (c) 2020 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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described in the Simplified BSD License. described in the Simplified BSD License.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Conventions Used in This Document . . . . . . . . . . . . 3 1.1. Conventions Used in This Document . . . . . . . . . . . . 3
2. Approaches to Partial Response Implementation . . . . . . . . 3 2. RDAP Path Segment Specification . . . . . . . . . . . . . . . 3
3. RDAP Path Segment Specification . . . . . . . . . . . . . . . 5 2.1. Subsetting Metadata . . . . . . . . . . . . . . . . . . . 3
3.1. Subsetting Metadata . . . . . . . . . . . . . . . . . . . 5 2.1.1. Representing Subsetting Links . . . . . . . . . . . . 4
3.1.1. Representing Subsetting Links . . . . . . . . . . . . 6 3. Dealing with Relationships . . . . . . . . . . . . . . . . . 5
4. Dealing with Relationships . . . . . . . . . . . . . . . . . 7 4. Basic Field Sets . . . . . . . . . . . . . . . . . . . . . . 5
5. Basic Field Sets . . . . . . . . . . . . . . . . . . . . . . 7 5. Negative Answers . . . . . . . . . . . . . . . . . . . . . . 7
6. Negative Answers . . . . . . . . . . . . . . . . . . . . . . 8 6. RDAP Conformance . . . . . . . . . . . . . . . . . . . . . . 8
7. RDAP Conformance . . . . . . . . . . . . . . . . . . . . . . 9 7. Implementation Status . . . . . . . . . . . . . . . . . . . . 8
8. Implementation Status . . . . . . . . . . . . . . . . . . . . 9 7.1. IIT-CNR/Registro.it . . . . . . . . . . . . . . . . . . . 8
8.1. IIT-CNR/Registro.it . . . . . . . . . . . . . . . . . . . 9 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 9. Security Considerations . . . . . . . . . . . . . . . . . . . 9
10. Security Considerations . . . . . . . . . . . . . . . . . . . 10 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9
11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 10 11. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 11 11.1. Normative References . . . . . . . . . . . . . . . . . . 9
12.1. Normative References . . . . . . . . . . . . . . . . . . 11 11.2. Informative References . . . . . . . . . . . . . . . . . 10
12.2. Informative References . . . . . . . . . . . . . . . . . 11 Appendix A. Approaches to Partial Response Implementation . . . 11
Appendix A. Change Log . . . . . . . . . . . . . . . . . . . . . 12 A.1. Specific Issues Raised by RDAP . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13 Appendix B. Change Log . . . . . . . . . . . . . . . . . . . . . 13
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 14
1. Introduction 1. Introduction
The use of partial response in RESTful API ([REST]) design is very The use of partial response in RESTful API ([REST]) design is very
common. The rationale is quite simple: instead of returning objects common. The rationale is quite simple: instead of returning objects
in API responses with all data fields, only a subset is returned. in API responses with all data fields, only a subset is returned.
The benefit is obvious: less data transferred over the network means The benefit is obvious: less data transferred over the network means
less bandwidth usage, faster server response, less CPU time spent less bandwidth usage, faster server response, less CPU time spent
both on the server and the client, as well as less memory usage on both on the server and the client, as well as less memory usage on
the client. the client.
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bibliographic catalogues, servers can provide responses according to bibliographic catalogues, servers can provide responses according to
different element sets (i.e. "brief" to get back a short response and different element sets (i.e. "brief" to get back a short response and
"full" to get back the complete response) "full" to get back the complete response)
Currently, RDAP does not provide a client with any way to request a Currently, RDAP does not provide a client with any way to request a
partial response: the server can only provide the client with the partial response: the server can only provide the client with the
full response ([RFC7483]). Furthermore, servers cannot define the full response ([RFC7483]). Furthermore, servers cannot define the
limits of the results according to partial responses and this causes limits of the results according to partial responses and this causes
strong inefficiencies. strong inefficiencies.
The protocol described in this specification extends RDAP search The protocol described in this specification extends RDAP search
capabilities to enable partial responses, by adding a new query capabilities to enable partial responses through the provisioning of
parameter and using a RESTful web service. The service is pre-defined sets of fields the user can request to an RDAP service by
implemented using the Hypertext Transfer Protocol (HTTP) ([RFC7230]) adding a new query parameter. The service is implemented using the
and the conventions described in RFC 7480 ([RFC7480]). Hypertext Transfer Protocol (HTTP) ([RFC7230]) and the conventions
described in RFC 7480 ([RFC7480]).
1.1. Conventions Used in This Document 1.1. Conventions Used in This Document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 ([RFC2119]). document are to be interpreted as described in RFC 2119 ([RFC2119]).
2. Approaches to Partial Response Implementation 2. RDAP Path Segment Specification
Looking at the implementation experiences described above, two
approaches to the implementation of partial response can be detected:
o the client declares explicitly the data fields to get back;
o the client declares a name identifying a server pre-defined set of
data fields.
The former is more flexible than the latter because clients can
specify all the data fields they need. However, it has some
drawbacks:
o fields have to be declared according to a given syntax. This is a
simple task when the data structure of the object is flat, but it
is much more difficult when the object has a tree structure like
the one of a JSON object. The presence of arrays and deep nested
objects contributes to complicate both the syntax definition of
the query and, consequently, the processing phase on the server
side;
o clients should perfectly know the returned data structure to avoid
cases when the requested fields are invalid;
o the 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 response that
ignores the unauthorized fields.
In addition to those listed above, RDAP responses raise some specific
issues:
o most of the relevant information of 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
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 the first approach, the Catnap Query
Language ([CQL]) is a comprehensive expression language that can be
used to customize the JSON response of a RESTful web service. The
practical application 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): in the first, only
objectClassName and ldhName are requested, in the second, 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 of CQL expressions for a search domain query
The latter approach seems to facilitate RDAP interoperability. In
fact, servers can define some basic field sets which, if known to the
clients, can increase the probability to get a valid response. The
usage of field sets lets the query string be less complex. In
addition, the definition of pre-defined sets of fields makes easier
to establish the results limits.
Finally, considering that there is not a real need for RDAP users to
have the maximum flexibility in defining all the possible sets of
logically connected fields (e.g. users interested in domains usually
need to know the status, the creation date, the expiry date of each
domain), the latter approach is preferred.
3. RDAP Path Segment Specification
The path segment defined in this section is an OPTIONAL extension of The path segment defined in this section is an OPTIONAL extension of
search path segments defined in RFC 7482 ([RFC7482]). This document search path segments defined in RFC 7482 ([RFC7482]). This document
defines an RDAP query parameter, "fieldSet", whose value is a string defines an RDAP query parameter, "fieldSet", whose value is a string
identifying a server pre-defined set of fields (Figure 2). identifying a server pre-defined set of fields (Figure 1).
This solution can be implemented by the RDAP providers with less
effort than fields selection and easily requested by consumers. The
considerations that has led to opt for this solution are reported in
more detail in Appendix A.
https://example.com/rdap/domains?name=example*.com&fieldSet=afieldset https://example.com/rdap/domains?name=example*.com&fieldSet=afieldset
Figure 2: Example of RDAP search query reporting the "fieldSet" Figure 1: Example of RDAP search query reporting the "fieldSet"
parameter parameter
3.1. Subsetting Metadata 2.1. Subsetting Metadata
According to most advanced principles in REST design, collectively According to most advanced principles in REST design, collectively
known as HATEOAS (Hypermedia as the Engine of Application State) known as HATEOAS (Hypermedia as the Engine of Application State)
([HATEOAS]), a client entering a REST application through an initial ([HATEOAS]), a client entering a REST application through an initial
URI should use the server-provided links to dynamically discover URI should use the server-provided links to dynamically discover
available actions and access the resources it needs. In this way, available actions and access the resources it needs. In this way,
the client is not requested to have prior knowledge of the service the client is not requested to have prior knowledge of the service
and, consequently, to hard code the URIs of different resources. and, consequently, to hard code the URIs of different resources.
This would allow the server to make URI changes as the API evolves This would allow the server to make URI changes as the API evolves
without breaking the clients. Definitively, a REST service should be without breaking the clients. Definitively, a REST service should be
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o "availableFieldSets": "AvailableFieldSet[]" (OPTIONAL) an array of o "availableFieldSets": "AvailableFieldSet[]" (OPTIONAL) an array of
objects each one describing an alternate available field set. objects each one describing an alternate available field set.
Members are: Members are:
* "name": "String" (REQUIRED) the field set name; * "name": "String" (REQUIRED) the field set name;
* "default": "Boolean" (REQUIRED) whether the field set is * "default": "Boolean" (REQUIRED) whether the field set is
applied by default; applied by default;
* "description": "String" (OPTIONAL) a human-readable description * "description": "String" (OPTIONAL) a human-readable description
of the field set; of the field set;
* "links": "Link[]" (OPTIONAL) an array of links as described in * "links": "Link[]" (OPTIONAL) an array of links as described in
RFC 8288 ([RFC8288]) containing the query string that applies RFC 8288 ([RFC8288]) containing the query string that applies
the field set. the field set.
3.1.1. Representing Subsetting Links 2.1.1. Representing Subsetting Links
An RDAP server MAY use the "links" array of the "subsetting_metadata" An RDAP server MAY use the "links" array of the "subsetting_metadata"
element to provide ready-made references ([RFC8288]) to the available element to provide ready-made references ([RFC8288]) to the available
field sets (Figure 3). Each link represents a reference to an field sets (Figure 2). Each link represents a reference to an
alternate view of the results. alternate view of the results.
{ {
"rdapConformance": [ "rdapConformance": [
"rdap_level_0", "rdap_level_0",
"subsetting_level_0" "subsetting_level_0"
], ],
... ...
"subsetting_metadata": { "subsetting_metadata": {
"currentFieldSet": "afieldset", "currentFieldSet": "afieldset",
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"type": "application/rdap+json" "type": "application/rdap+json"
}, },
... ...
] ]
}, },
"domainSearchResults": [ "domainSearchResults": [
... ...
] ]
} }
Figure 3: Example of a "subsetting_metadata" instance Figure 2: Example of a "subsetting_metadata" instance
4. Dealing with Relationships 3. Dealing with Relationships
Some additional considerations can be made about how second level Some additional considerations can be made about how second level
objects could be represented within a field set. In fact, since the objects could be represented within a field set. In fact, since the
topmost objects could be returned according to different field sets, topmost objects could be returned according to different field sets,
the same thing could go for their related objects. As a consequence, the same thing could go for their related objects. As a consequence,
the response could contain either no relationship or associated the response could contain either no relationship or associated
objects which are in turn provided according to a field set. objects which are in turn provided according to a field set.
5. Basic Field Sets 4. Basic Field Sets
In order to improve interoperability between clients and servers, the In order to improve interoperability between clients and servers, the
name, as well as the list of fields for each field set, should be name, as well as the list of fields for each field set, should be
shared by most of RDAP providers. This section defines three basic shared by most of RDAP providers. This section defines three basic
field sets which servers MAY implement to facilitate their field sets which servers MAY implement to facilitate their
interaction with clients: interaction with clients:
o "id": the server provides only the key field, respectively: o "id": the server provides only the key field, respectively:
"handle" for entities, "ldhName" for domains and nameservers. If "handle" for entities, "ldhName" for domains and nameservers. If
a returned domain or nameserver is an IDN ([RFC5890]), then the a returned domain or nameserver is an IDN ([RFC5890]), then the
"unicodeName" field MUST be included in the response. This field "unicodeName" field MUST be included in the response. This field
set could be used when the client wants to simply obtain a set could be used when the client wants to simply obtain a
collection of object identifiers (Figure 4); collection of object identifiers (Figure 3);
o "brief": it contains the fields that can be included in a "short" o "brief": it contains the fields that can be included in a "short"
response. This field set could be used when the client is asking response. This field set could be used when the client is asking
for a subset of the full response which gives a basic knowledge of for a subset of the full response which gives a basic knowledge of
each object; each object;
o "full": it contains all the information the server can provide for o "full": it contains all the information the server can provide for
a particular object. a particular object.
The "objectClassName" field is implicitly included in each of the The "objectClassName" field is implicitly included in each of the
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"rel": "self", "rel": "self",
"href": "https://example.com/rdap/domain/example2.com", "href": "https://example.com/rdap/domain/example2.com",
"type": "application/rdap+json" "type": "application/rdap+json"
} }
], ],
}, },
... ...
] ]
} }
Figure 4: Example of RDAP response according to the "id" field set Figure 3: Example of RDAP response according to the "id" field set
6. Negative Answers 5. Negative Answers
Each request including an unsupported field set SHOULD obtain an HTTP Each request including an unsupported field set SHOULD obtain an HTTP
400 (Bad Request) response code. 400 (Bad Request) response code.
Optionally, the response MAY include additional information regarding Optionally, the response MAY include additional information regarding
the negative answer in the HTTP entity body. the negative answer in the HTTP entity body.
7. RDAP Conformance 6. RDAP Conformance
Servers returning the "subsetting_metadata" section in their Servers returning the "subsetting_metadata" section in their
responses MUST include "subsetting_level_0" in the rdapConformance responses MUST include "subsetting_level_0" in the rdapConformance
array. array.
8. Implementation Status 7. Implementation Status
NOTE: Please remove this section and the reference to RFC 7942 prior NOTE: Please remove this section and the reference to RFC 7942 prior
to publication as an RFC. to publication as an RFC.
This section records the status of known implementations of the This section records the status of known implementations of the
protocol defined by this specification at the time of posting of this protocol defined by this specification at the time of posting of this
Internet-Draft, and is based on a proposal described in RFC 7942 Internet-Draft, and is based on a proposal described in RFC 7942
([RFC7942]). The description of implementations in this section is ([RFC7942]). The description of implementations in this section is
intended to assist the IETF in its decision processes in progressing intended to assist the IETF in its decision processes in progressing
drafts to RFCs. Please note that the listing of any individual drafts to RFCs. Please note that the listing of any individual
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implementations or their features. Readers are advised to note that implementations or their features. Readers are advised to note that
other implementations may exist. other implementations may exist.
According to RFC 7942, "this will allow reviewers and working groups According to RFC 7942, "this will allow reviewers and working groups
to assign due consideration to documents that have the benefit of to assign due consideration to documents that have the benefit of
running code, which may serve as evidence of valuable experimentation running code, which may serve as evidence of valuable experimentation
and feedback that have made the implemented protocols more mature. and feedback that have made the implemented protocols more mature.
It is up to the individual working groups to use this information as It is up to the individual working groups to use this information as
they see fit". they see fit".
8.1. IIT-CNR/Registro.it 7.1. IIT-CNR/Registro.it
Responsible Organization: Institute of Informatics and Telematics Responsible Organization: Institute of Informatics and Telematics
of National Research Council (IIT-CNR)/Registro.it of National Research Council (IIT-CNR)/Registro.it
Location: https://rdap.pubtest.nic.it/ Location: https://rdap.pubtest.nic.it/
Description: This implementation includes support for RDAP queries Description: This implementation includes support for RDAP queries
using data from .it public test environment. using data from .it public test environment.
Level of Maturity: This is a "proof of concept" research Level of Maturity: This is an "alpha" test implementation.
implementation.
Coverage: This implementation includes all of the features Coverage: This implementation includes all of the features
described in this specification. described in this specification.
Contact Information: Mario Loffredo, mario.loffredo@iit.cnr.it Contact Information: Mario Loffredo, mario.loffredo@iit.cnr.it
9. IANA Considerations 8. IANA Considerations
IANA is requested to register the following value in the RDAP IANA is requested to register the following value in the RDAP
Extensions Registry: Extensions Registry:
Extension identifier: subsetting Extension identifier: subsetting
Registry operator: Any Registry operator: Any
Published specification: This document. Published specification: This document.
Contact: IESG <iesg@ietf.org> Contact: IESG <iesg@ietf.org>
Intended usage: This extension describes a best practice for Intended usage: This extension describes a best practice for
partial response provisioning. partial response provisioning.
10. Security Considerations 9. Security Considerations
The search query typically requires more server resources (such as The search query typically requires more server resources (such as
memory, CPU cycles, and network bandwidth) when compared to the memory, CPU cycles, and network bandwidth) when compared to the
lookup query. This increases the risk of server resource exhaustion lookup query. This increases the risk of server resource exhaustion
and subsequent denial of service due to abuse. Partial response can and subsequent denial of service due to abuse. Partial response can
contribute together with other strategies (e.g. restricting search contribute together with other strategies (e.g. restricting search
functionality, limiting the rate of search requests, truncating and functionality, limiting the rate of search requests, truncating and
paging results) to mitigate this risk. paging results) to mitigate this risk.
Furthermore, partial response can support RDAP operators to implement Furthermore, partial response can support RDAP operators to implement
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o some field sets could be available only to some users. o some field sets could be available only to some users.
Servers can also define different results limits according to the Servers can also define different results limits according to the
available field sets, so a more flexible truncation strategy can be available field sets, so a more flexible truncation strategy can be
realized. realized.
Therefore, the new query parameter presented in this document Therefore, the new query parameter presented in this document
provides the RDAP operators with a way to implement a secure server provides the RDAP operators with a way to implement a secure server
without penalizing its efficiency. without penalizing its efficiency.
11. Acknowledgements 10. Acknowledgements
The authors would like to acknowledge Scott Hollenbeck and Tom The authors would like to acknowledge Scott Hollenbeck, Tom Harrison
Harrison for their contribution to this document. and Karl Heinz Wolf for their contribution to this document.
12. References 11. References
12.1. Normative References 11.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
[RFC5890] Klensin, J., "Internationalized Domain Names for [RFC5890] Klensin, J., "Internationalized Domain Names for
Applications (IDNA): Definitions and Document Framework", Applications (IDNA): Definitions and Document Framework",
RFC 5890, DOI 10.17487/RFC5890, August 2010, RFC 5890, DOI 10.17487/RFC5890, August 2010,
<https://www.rfc-editor.org/info/rfc5890>. <https://www.rfc-editor.org/info/rfc5890>.
skipping to change at page 11, line 48 skipping to change at page 10, line 44
[RFC7483] Newton, A. and S. Hollenbeck, "JSON Responses for the [RFC7483] Newton, A. and S. Hollenbeck, "JSON Responses for the
Registration Data Access Protocol (RDAP)", RFC 7483, Registration Data Access Protocol (RDAP)", RFC 7483,
DOI 10.17487/RFC7483, March 2015, DOI 10.17487/RFC7483, March 2015,
<https://www.rfc-editor.org/info/rfc7483>. <https://www.rfc-editor.org/info/rfc7483>.
[RFC8288] Nottingham, M., "Web Linking", RFC 8288, [RFC8288] Nottingham, M., "Web Linking", RFC 8288,
DOI 10.17487/RFC8288, October 2017, DOI 10.17487/RFC8288, October 2017,
<https://www.rfc-editor.org/info/rfc8288>. <https://www.rfc-editor.org/info/rfc8288>.
12.2. Informative References 11.2. Informative References
[CQL] Whitaker, G., "Catnap Query Language Reference", September [CQL] Whitaker, G., "Catnap Query Language Reference", September
2017, <https://github.com/gregwhitaker/catnap/wiki/ 2017, <https://github.com/gregwhitaker/catnap/wiki/Catnap-
Catnap-Query-Language-Reference>. Query-Language-Reference>.
[FACEBOOK] [FACEBOOK]
facebook.com, "facebook for developers - Using the Graph facebook.com, "facebook for developers - Using the Graph
API", July 2017, <https://developers.facebook.com/docs/ API", July 2017, <https://developers.facebook.com/docs/
graph-api/using-graph-api>. graph-api/using-graph-api>.
[GOOGLE] google.com, "Making APIs Faster: Introducing Partial [GOOGLE] google.com, "Making APIs Faster: Introducing Partial
Response and Partial Update", March 2010, Response and Partial Update", March 2010,
<http://googlecode.blogspot.it/2010/03/ <http://googlecode.blogspot.it/2010/03/making-apis-faster-
making-apis-faster-introducing-partial.html>. introducing-partial.html>.
[HATEOAS] Jedrzejewski, B., "HATEOAS - a simple explanation", 2018, [HATEOAS] Jedrzejewski, B., "HATEOAS - a simple explanation", 2018,
<https://www.e4developer.com/2018/02/16/ <https://www.e4developer.com/2018/02/16/hateoas-simple-
hateoas-simple-explanation/>. explanation/>.
[LINKEDIN] [LINKEDIN]
linkedin.com, "Java One 2009: Building Consistent RESTful linkedin.com, "Java One 2009: Building Consistent RESTful
APIs in a High Performance Environment", July 2009, APIs in a High Performance Environment", July 2009,
<https://blog.linkedin.com/2009/07/08/brandon-duncan-java- <https://blog.linkedin.com/2009/07/08/brandon-duncan-java-
one-building-consistent-restful-apis-in-a-high- one-building-consistent-restful-apis-in-a-high-
performance-environment>. performance-environment>.
[REST] Fielding, R., "Architectural Styles and the Design of [REST] Fielding, R., "Architectural Styles and the Design of
Network-based Software Architectures", 2000, Network-based Software Architectures", 2000,
skipping to change at page 12, line 43 skipping to change at page 11, line 43
Edition", September 2015. Edition", September 2015.
[REST-API2] [REST-API2]
Masse, M., "REST API Design Rulebook", October 2011. Masse, M., "REST API Design Rulebook", October 2011.
[RFC7942] Sheffer, Y. and A. Farrel, "Improving Awareness of Running [RFC7942] Sheffer, Y. and A. Farrel, "Improving Awareness of Running
Code: The Implementation Status Section", BCP 205, Code: The Implementation Status Section", BCP 205,
RFC 7942, DOI 10.17487/RFC7942, July 2016, RFC 7942, DOI 10.17487/RFC7942, July 2016,
<https://www.rfc-editor.org/info/rfc7942>. <https://www.rfc-editor.org/info/rfc7942>.
Appendix A. Change Log Appendix A. Approaches to Partial Response Implementation
Looking at the implementation experiences described in Section 1, two
approaches to the implementation of partial response can be detected:
o the client declares explicitly the data fields to get back;
o the client declares a name identifying a server pre-defined set of
data fields.
The former is more flexible than the latter because clients can
specify all the data fields they need. However, it has some
drawbacks:
o fields have to be declared according to a given syntax. This is a
simple task when the data structure of the object is flat, but it
is much more difficult when the object has a tree structure like
the one of a JSON object. The presence of arrays and deep nested
objects contributes to complicate both the syntax definition of
the query and, consequently, the processing phase on the server
side;
o clients should perfectly know the returned data structure to avoid
cases when the requested fields are invalid;
o the 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 response that
ignores the 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 relevant information of 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
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 the first approach, the Catnap Query
Language ([CQL]) is a comprehensive expression language that can be
used to customize the JSON response of a RESTful web service. The
practical application 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 4): in the first, only
objectClassName and ldhName are requested, in the second, 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 4: Examples of CQL expressions for a search domain query
The latter approach seems to facilitate RDAP interoperability. In
fact, servers can define some basic field sets which, if known to the
clients, can increase the probability to get a valid response. The
usage of field sets lets the query string be less complex. In
addition, the definition of pre-defined sets of fields makes easier
to establish the results limits.
Finally, considering that there is not a real need for RDAP users to
have the maximum flexibility in defining all the possible sets of
logically connected fields (e.g. users interested in domains usually
need to know the status, the creation date, the expiry date of each
domain), the latter approach is preferred.
Appendix B. Change Log
00: Initial working group version ported from draft-loffredo-regext- 00: Initial working group version ported from draft-loffredo-regext-
rdap-partial-response-03 rdap-partial-response-03
01: Removed "FOR DISCUSSION" items. Changed the basic field sets 01: Removed "FOR DISCUSSION" items. Changed the basic field sets
from REQUIRED to OPTIONAL. Removed the definition of fields from REQUIRED to OPTIONAL. Removed the definition of fields
included in "brief" field set. Provided a more detailed included in "brief" field set. Provided a more detailed
description of "subsetting_metadata" structure. Removed some description of "subsetting_metadata" structure. Removed some
references. references.
02: Added the "Negative Answers" section. Changed "IANA 02: Added the "Negative Answers" section. Changed "IANA
Considerations" section. Considerations" section.
03: Added the "unicodeName" field in the id fieldSet when a returned 03: Added the "unicodeName" field in the id fieldSet when a returned
domain or nameserver is an IDN. Added RFC5890 to "Normative domain or nameserver is an IDN. Added RFC5890 to "Normative
References" section. References" section.
04: Recommended the RDAP providers to include a "self" link in any 04: Recommended the RDAP providers to include a "self" link in any
field set other than "full". Updated "Acknowledgements" section. field set other than "full". Updated "Acknowledgements" section.
05: Moved "Approaches to Partial Response Implementation" section to
the appendix.
Authors' Addresses Authors' Addresses
Mario Loffredo Mario Loffredo
IIT-CNR/Registro.it IIT-CNR/Registro.it
Via Moruzzi,1 Via Moruzzi,1
Pisa 56124 Pisa 56124
IT IT
Email: mario.loffredo@iit.cnr.it Email: mario.loffredo@iit.cnr.it
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