Diff: rfc8982xml2.original.xml

	rfc8982xml2.original.xml	rfc8982.xml
	<?xml version="1.0" encoding="UTF-8"?>	<?xml version="1.0" encoding="UTF-8"?>

	<!DOCTYPE rfc SYSTEM "http://xml.resource.org/authoring/rfc2629.dtd"
	[
	<!ENTITY RFC2119 PUBLIC ''
	'http://xml.resource.org/public/rfc/bibxml/reference.RFC.2119.xml'>
	<!ENTITY RFC5890 PUBLIC ''
	'http://xml.resource.org/public/rfc/bibxml/reference.RFC.5890.xml'>
	<!ENTITY RFC7230 PUBLIC ''
	'http://xml.resource.org/public/rfc/bibxml/reference.RFC.7230.xml'>
	<!ENTITY RFC7480 PUBLIC ''
	'http://xml.resource.org/public/rfc/bibxml/reference.RFC.7480.xml'>
	<!ENTITY RFC7481 PUBLIC ''
	'http://xml.resource.org/public/rfc/bibxml/reference.RFC.7481.xml'>
	<!ENTITY RFC7482 PUBLIC ''
	'http://xml.resource.org/public/rfc/bibxml/reference.RFC.7482.xml'>
	<!ENTITY RFC7483 PUBLIC ''
	'http://xml.resource.org/public/rfc/bibxml/reference.RFC.7483.xml'>
	<!ENTITY RFC7942 PUBLIC ''
	'http://xml.resource.org/public/rfc/bibxml/reference.RFC.7942.xml'>
	<!ENTITY RFC8174 PUBLIC ''
	'http://xml.resource.org/public/rfc/bibxml/reference.RFC.8174.xml'>
	<!ENTITY RFC8288 PUBLIC ''
	'http://xml.resource.org/public/rfc/bibxml/reference.RFC.8288.xml'>
	]>
	<?xml-stylesheet type="text/xsl" href="rfc2629.xslt"?>


	<?rfc toc="yes"?>	<!DOCTYPE rfc SYSTEM "rfc2629-xhtml.ent">
	<?rfc tocompact="yes"?>
	<?rfc tocdepth="4"?>	<rfc xmlns:xi="http://www.w3.org/2001/XInclude" xml:lang="en" submissionType="IE
	<?rfc compact="yes"?>	TF"
	<?rfc subcompact="yes"?>	category="std" consensus="true" docName="draft-ietf-regext-rdap-partial-response
	<?rfc sortrefs="yes"?>	-16"
	<?rfc symrefs="yes"?>	number="8982" ipr="trust200902" tocInclude="true" tocDepth="4" sortRefs="true"
	<?rfc iprnotified="no"?>	symRefs="true" version="3">


	<rfc category="std" docName="draft-ietf-regext-rdap-partial-response-16" ipr="tr ust200902">
	<front>	<front>
	<title abbrev="RDAP Partial Response">Registration Data Access Protocol (RDA P) Partial Response</title>	<title abbrev="RDAP Partial Response">Registration Data Access Protocol (RDA P) Partial Response</title>

		<seriesInfo name="RFC" value="8982"/>
	<author fullname="Mario Loffredo" initials="M." surname="Loffredo">	<author fullname="Mario Loffredo" initials="M." surname="Loffredo">
	<organization>IIT-CNR/Registro.it</organization>	<organization>IIT-CNR/Registro.it</organization>
	<address>	<address>
	<postal>	<postal>
	<street>Via Moruzzi,1</street>	<street>Via Moruzzi,1</street>
	<city>Pisa</city>	<city>Pisa</city>
	<country>IT</country>	<country>IT</country>
	<code>56124</code>	<code>56124</code>
	</postal>	</postal>
	<email>mario.loffredo@iit.cnr.it</email>	<email>mario.loffredo@iit.cnr.it</email>

	<uri>http://www.iit.cnr.it</uri>	<uri>https://www.iit.cnr.it</uri>
	</address>	</address>
	</author>	</author>


	<author fullname="Maurizio Martinelli" initials="M." surname="Martinelli">	<author fullname="Maurizio Martinelli" initials="M." surname="Martinelli">
	<organization>IIT-CNR/Registro.it</organization>	<organization>IIT-CNR/Registro.it</organization>
	<address>	<address>
	<postal>	<postal>
	<street>Via Moruzzi,1</street>	<street>Via Moruzzi,1</street>
	<city>Pisa</city>	<city>Pisa</city>
	<country>IT</country>	<country>IT</country>
	<code>56124</code>	<code>56124</code>
	</postal>	</postal>
	<email>maurizio.martinelli@iit.cnr.it</email>	<email>maurizio.martinelli@iit.cnr.it</email>

	skipping to change at line 64 ¶	skipping to change at line 36 ¶
	<author fullname="Maurizio Martinelli" initials="M." surname="Martinelli">	<author fullname="Maurizio Martinelli" initials="M." surname="Martinelli">
	<organization>IIT-CNR/Registro.it</organization>	<organization>IIT-CNR/Registro.it</organization>
	<address>	<address>
	<postal>	<postal>
	<street>Via Moruzzi,1</street>	<street>Via Moruzzi,1</street>
	<city>Pisa</city>	<city>Pisa</city>
	<country>IT</country>	<country>IT</country>
	<code>56124</code>	<code>56124</code>
	</postal>	</postal>
	<email>maurizio.martinelli@iit.cnr.it</email>	<email>maurizio.martinelli@iit.cnr.it</email>

	<uri>http://www.iit.cnr.it</uri>	<uri>https://www.iit.cnr.it</uri>
	</address>	</address>
	</author>	</author>

		<date year="2021" month="February"/>
	<date/>
	<area>Applications and Real-Time</area>	<area>Applications and Real-Time</area>
	<workgroup>Registration Protocols Extensions</workgroup>	<workgroup>Registration Protocols Extensions</workgroup>
	<keyword>RDAP</keyword>	<keyword>RDAP</keyword>
	<keyword>Partial response</keyword>	<keyword>Partial response</keyword>


	<abstract>	<abstract>
	<t>The Registration Data Access Protocol (RDAP) does not include capabilit ies to request partial responses. Servers will only return full responses that include all of the information that a client is authorized to receive. A partia l response capability that limits the amount of information returned, 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 specif y their preference for obtaining a partial response.</t>	<t>The Registration Data Access Protocol (RDAP) does not include capabilit ies to request partial responses. Servers will only return full responses that include all of the information that a client is authorized to receive. A partia l response capability that limits the amount of information returned, 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 specif y their preference for obtaining a partial response.</t>
	</abstract>	</abstract>
	</front>	</front>


	<middle>	<middle>

	<section anchor="introduction" title="Introduction">	<section anchor="introduction">
	<t>The use of partial responses in RESTful API <xref target="REST"/> desig
	n is very common. The rationale is quite simple: instead of returning objects i
	n API responses with all data fields, only a subset of the fields in each result
	object is returned. The benefit is obvious: less data transferred over the net
	work means less bandwidth usage, faster server responses, less CPU time spent bo
	th on the server and the client, and less memory usage on the client.</t>

	<t>Currently, RDAP does not provide a client with any way to request a par
	tial response. Servers can only provide the client with a full response <xref t
	arget="RFC7483"/>. Servers cannot limit the amount of information returned in a
	response based on a client's preferences, and this creates inefficiencies.</t>


	<t>The protocol described in this specification extends RDAP search capabi	<name>Introduction</name>
	lities to enable partial responses through the provisioning of pre-defined sets	<t>The use of partial responses in RESTful API <xref
	of fields that clients can submit to an RDAP service by adding a new query param	target="REST"/> design is very common. The rationale is quite simple:
	eter. The service is implemented using the Hypertext Transfer Protocol (HTTP) <	instead of returning objects in API responses with all data fields, only
	xref target="RFC7230"/> and the conventions described in <xref target="RFC7480"/	a subset of the fields in each result object is returned. The benefit
	>.</t>	is obvious: less data transferred over the network means less bandwidth
		usage, faster server responses, less CPU time spent both on the server
		and the client, and less memory usage on the client.</t>


	<section title="Conventions Used in This Document">	<t>Currently, RDAP does not provide a client with any way to request a
	<t>The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "S	partial response. Servers can only provide the client with a full
	HOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in	response <xref target="RFC7483"/>. Servers cannot limit the amount of
	this document are to be interpreted as described in BCP 14 <xref target="RFC211	information returned in a response based on a client's preferences, and
	9"/> <xref target="RFC8174"/> when, and only when, they appear in all capitals,	this creates inefficiencies.</t>
	as shown here.</t>	<t>The protocol described in this specification extends RDAP search
	</section>	capabilities to enable partial responses through the provisioning of
	</section>	predefined sets of fields that clients can submit to an RDAP service by
		adding a new query parameter. The service is implemented using the
		Hypertext Transfer Protocol (HTTP) <xref target="RFC7230"/> and the
		conventions described in <xref target="RFC7480"/>.</t>
		<section>
		<name>Conventions Used in This Document</name>


	<section anchor="rdap-path-segment-specification" title="RDAP Path Segment	<t>
	Specification">	The key words "<bcp14>MUST</bcp14>", "<bcp14>MUST NOT</bcp14>",
		"<bcp14>REQUIRED</bcp14>", "<bcp14>SHALL</bcp14>", "<bcp14>SHALL
		NOT</bcp14>", "<bcp14>SHOULD</bcp14>", "<bcp14>SHOULD NOT</bcp14>",
		"<bcp14>RECOMMENDED</bcp14>", "<bcp14>NOT RECOMMENDED</bcp14>",
		"<bcp14>MAY</bcp14>", and "<bcp14>OPTIONAL</bcp14>" in this document are
		to be interpreted as described in BCP 14 <xref target="RFC2119"/>
		<xref target="RFC8174"/> when, and only when, they appear in all capitals,
		as shown here.
		</t>


	<t>The path segment defined in this section is an OPTIONAL extension of s	</section>
	earch path segments defined in <xref target="RFC7482"/>. This document defines	</section>
	an RDAP query parameter, "fieldSet", whose value is a non-empty string	<section anchor="rdap-path-segment-specification">
	identifying a server-defined set of fields returned in place of the full respon	<name>RDAP Path Segment Specification</name>
	se. The field sets supported by a server are usually described in out-of-band d	<t>The path segment defined in this section is an
	ocuments (e.g., RDAP profile) together with other features. Moreover, this docu	<bcp14>OPTIONAL</bcp14> extension of search path segments defined in
	ment defines in <xref target="rdap-subsetting-metadata"/> an in-band mechanism b	<xref target="RFC7482"/>. This document defines an RDAP query
	y means of which servers can provide clients with a basic information about the	parameter, "fieldSet", whose value is a non-empty string identifying a
	supported field sets.</t>	server-defined set of fields returned in place of the full response.
		The field sets supported by a server are usually described in
		out-of-band documents (e.g., RDAP profile) together with other features.
		Moreover, this document defines in <xref
		target="rdap-subsetting-metadata"/> an in-band mechanism by means of
		which servers can provide clients with basic information about the
		supported field sets.</t>
		<t>The following is an example of an RDAP query including the "fieldSet" p
		arameter:</t>
		<artwork><![CDATA[
		https://example.com/rdap/domains?name=example*.com&fieldSet=afieldset
		]]></artwork>
		<t>This solution can be implemented by RDAP providers with less effort
		than field selection and is easily requested by clients. The
		considerations that have led to this solution are described in more
		detail in <xref
		target="approaches-to-partial-response-implementation"/>.</t>
		<section anchor="rdap-subsetting-metadata">


	<t>The following is an example of an RDAP query including the "fiel	<name>Subsetting Metadata</name>
	dSet" parameter:</t>	<t>According to most advanced principles in REST design, collectively
		known as "Hypermedia as the Engine of Application State" (HATEOAS)
		<xref target="HATEOAS"/>, a client entering a REST application through
		an initial URI should use server-provided links to dynamically
		discover available actions and access the resources it needs. In this
		way, the client is not required to have prior knowledge of the service
		nor, consequently, to hard-code the URIs of different resources. This
		allows the server to make URI changes as the API evolves without
		breaking clients. Definitively, a REST service should be as
		self-descriptive as possible.</t>
		<t>Therefore, servers implementing the query parameter described in
		this specification <bcp14>SHOULD</bcp14> provide additional
		information in their responses about the available field sets. Such
		information is collected in a new JSON data structure named
		"subsetting_metadata" containing the following properties:</t>
		<dl newline="true">


	<t>https://example.com/rdap/domains?name=example*.com&fieldSet=afiel	<dt>"currentFieldSet": "String" (<bcp14>REQUIRED</bcp14>)
	dset</t>	</dt>
		<dd>either the value of the "fieldSet" parameter as specified in the query
		string, or the field set applied by default.
		</dd>


	<t>This solution can be implemented by RDAP providers with less effort th	<dt>"availableFieldSets": "AvailableFieldSet[]" (<bcp14>OPTIONAL</bcp14>)
	an field selection and is easily requested by clients. The considerations that	</dt>
	have led to this solution are described in more detail in <xref target="approach	<dd><t>an array of objects, with each element describing an available field set.
	es-to-partial-response-implementation"/>.</t>	The AvailableFieldSet object includes the following members:</t>


	<section anchor="rdap-subsetting-metadata" title="Subsetting Metadata">	<dl newline="true">


	<t>According to most advanced principles in REST design, collectively known	<dt>"name": "String" (<bcp14>REQUIRED</bcp14>)
	as HATEOAS (Hypermedia as the Engine of Application State) <xref target="HATEOA	</dt>
	S"/>, a client entering a REST application through an initial URI should use ser	<dd>the field set name.
	ver-provided links to dynamically discover available actions and access the reso	</dd>
	urces it needs. In this way, the client is not required to have prior knowledge
	of the service and, consequently, to hard code the URIs of different resources.
	This allows the server to make URI changes as the API evolves without breaking
	clients. Definitively, a REST service should be as self-descriptive as possibl
	e.</t>


	<t>Therefore, servers implementing the query parameter described in this s	<dt>"default": "Boolean" (<bcp14>REQUIRED</bcp14>)
	pecification SHOULD provide additional information in their responses about the	</dt>
	available field sets. Such information is collected in a new JSON data structur	<dd>indicator of whether the field set is applied by
	e named "subsetting_metadata" containing the following properties:</t>	default. An RDAP server <bcp14>MUST</bcp14> define only one default field set.
	<t><list style="symbols">	</dd>
	<t>"currentFieldSet": "String" (REQUIRED) either th
	e value of the "fieldSet" parameter as specified in the query string,
	or the field set applied by default;<vspace blankLines='1'/></t>
	<t>"availableFieldSets": "AvailableFieldSet[]" (OP
	TIONAL) an array of objects, with each element describing an available field set
	. The AvailableFieldSet object includes the following members:
	<list style="symbols">
	<t>"name": "String" (REQUIRED) the field set nam
	e;</t>
	<t>"default": "Boolean" (REQUIRED) whether the fie
	ld set is applied by default. An RDAP server MUST define only one default field
	set;</t>
	<t>"description": "String" (OPTIONAL) a human-rea
	dable description of the field set;</t>
	<t>"links": "Link[]" (OPTIONAL) an array of links a
	s described in <xref target="RFC8288"/> containing the query string that applies
	the field set (see <xref target="subsetting_links"/>).</t>
	</list></t>
	</list></t>


	<section anchor="rdap-conformance" title="RDAP Conformance">	<dt>"description": "String" (<bcp14>OPTIONAL</bcp14>)
	<t>Servers returning the "subsetting_metadata" section in their	</dt>
	responses MUST include "subsetting" in the rdapConformance array.</t>	<dd>a human-readable description of the field set.
	</section>	</dd>


	<section anchor="subsetting_links" title="Representing Subsetting Links">	<dt>"links": "Link[]" (<bcp14>OPTIONAL</bcp14>)
	<t>An RDAP server MAY use the "links" array of the "subset	</dt>
	ting_metadata" element to provide ready-made references <xref target="RFC82	<dd>an array of links as described in <xref target="RFC8288"/> containing the
	88"/> to the available field sets (<xref target="subset-link-in-response-example	query string that applies the field set (see <xref
	"/>). The target URI in each link is the reference to an alternative to the cur	target="subsetting_links"/>).
	rent view of results identified by the context URI.</t>	</dd>
		</dl>


	<t>The "value", "rel" and "href" JSON values MUST	</dd>
	be specified. All other JSON values are OPTIONAL.</t>	</dl>


	<figure anchor="subset-link-in-response-example" title="Example of a "	<section anchor="rdap-conformance">
	subsetting_metadata" instance">	<name>RDAP Conformance</name>
	<artwork xml:space="preserve"><![CDATA[	<t>Servers returning the "subsetting_metadata" section in their respon
		ses <bcp14>MUST</bcp14> include "subsetting" in the rdapConformance array.</t>
		</section>
		<section anchor="subsetting_links">
		<name>Representing Subsetting Links</name>
		<t>An RDAP server <bcp14>MAY</bcp14> use the "links" array of the "sub
		setting_metadata" element to provide ready-made references <xref target="RFC8288
		"/> to the available field sets (<xref target="subset-link-in-response-example"/
		>). The target URI in each link is the reference to an alternative to the curre
		nt view of results identified by the context URI.</t>
		<t>The "value", "rel", and "href" JSON values <bcp14>MUST</bcp14> be s
		pecified. All other JSON values are <bcp14>OPTIONAL</bcp14>.</t>
		<figure anchor="subset-link-in-response-example">
		<name>Example of a "subsetting_metadata" Instance</name>


		<sourcecode type="json"><![CDATA[
	{	{
	"rdapConformance": [	"rdapConformance": [
	"rdap_level_0",	"rdap_level_0",
	"subsetting"	"subsetting"
	],	],
	...	...
	"subsetting_metadata": {	"subsetting_metadata": {
	"currentFieldSet": "afieldset",	"currentFieldSet": "afieldset",
	"availableFieldSets": [	"availableFieldSets": [
	{	{

	skipping to change at line 163 ¶	skipping to change at line 214 ¶
	]	]
	},	},
	...	...
	]	]
	},	},
	...	...
	"domainSearchResults": [	"domainSearchResults": [
	...	...
	]	]
	}	}

	]]></artwork>	]]></sourcecode>
	</figure>	</figure>
		</section>
	</section>
	</section>
	</section>	</section>

		</section>
		<section anchor="rdap-field-set-relationships">
		<name>Dealing with Relationships</name>
		<t>Representation of second-level objects within a field set produces addi
		tional considerations. Since the representation of the topmost returned objects
		will vary according to the field set in use, the response may contain no relati
		onships (e.g., for an abbreviated field set) or may contain associated objects a
		s in a normal RDAP query response. Each field set can indicate the format of th
		e additional objects to be returned, in the same manner that the format of the t
		opmost objects is controlled by the field set.</t>
		</section>
		<section anchor="basic-field-sets">
		<name>Basic Field Sets</name>
		<t>This section defines three basic field sets that servers
		<bcp14>MAY</bcp14> implement to facilitate their interaction with
		clients:</t>


	<section anchor="rdap-field-set-relationships" title="Dealing with Relationships	<dl>
	">
	<t>Representation of second level objects within a field set produces add
	itional considerations. Since the representation of the topmost returned object
	s will vary according to the field set in use, the response may contain no relat
	ionships (e.g., for an abbreviated field set) or may contain associated objects
	as in a normal RDAP query response. Each field set can indicate the format of t
	he additional objects to be returned, in the same manner that the format of the
	topmost objects is controlled by the field set.</t>
	</section>

	<section anchor="basic-field-sets" title="Basic Field Sets">

	<t>This section defines three basic field sets which servers MAY implemen
	t to facilitate their interaction with clients:</t>


	<t><list style="symbols">	<dt>"id":
	<t>"id": the server provides only the key field: "handle	</dt>
	" for entities, "ldhName" for domains and nameservers. If a retu	<dd>The server provides only the key field; "handle" for entities, and "ldhName"
	rned domain or nameserver is an Internationalized Domain Name (IDN) <xref target	for domains
	="RFC5890"/>, then the "unicodeName" field MUST additionally be includ	and nameservers. If a returned domain or nameserver is an Internationalized Dom
	ed in the response. This field set could be used when the client wants to obtai	ain Name (IDN) <xref
	n a collection of object identifiers (<xref target="fieldSet-id-response-example	target="RFC5890"/>, then the "unicodeName" field <bcp14>MUST</bcp14> additionall
	"/>);<vspace blankLines='1' /></t>	y be included in the
	<t>"brief": the field set contains the fields that can be inc	response. This field set could be used when the client wants to obtain a collec
	luded in a "short" response. This field set could be used when the cl	tion of object
	ient is asking for a subset of the full response which provides only basic knowl	identifiers (<xref target="fieldSet-id-response-example"/>).
	edge of each object;<vspace blankLines='1'/></t>	</dd>
	<t>"full": the field set contains all of the information the
	server can provide for a particular object.</t>
	</list></t>


	<t>The "objectClassName" field is implicitly included in each of	<dt>"brief":
	the above field sets. RDAP providers SHOULD include a "links" field	</dt>
	indicating the "self" link relationship. RDAP providers MAY also add	<dd>The field set contains the fields that can be included in a "short" response
	any property providing service information.</t>	.
		This field set could be used when the client is asking for a subset of the full
		response that provides
		only basic knowledge of each object.
		</dd>


	<t>Fields included in the "brief" and "full" field set	<dt>"full":
	responses MUST take into account the user's access and authorization levels.</t	</dt>
	>	<dd>The field set contains all of the information the server can provide for a
		particular object.
		</dd>


	<figure anchor="fieldSet-id-response-example" title="Example of RDAP respo	</dl>
	nse according to the "id" field set">
	<artwork xml:space="preserve">


		<t>The "objectClassName" field is implicitly included in each of the above
		field sets. RDAP providers <bcp14>SHOULD</bcp14> include a "links" field indic
		ating the "self" link relationship. RDAP providers <bcp14>MAY</bcp14> also add
		any property providing service information.</t>
		<t>Fields included in the "brief" and "full" field set responses <bcp14>MU
		ST</bcp14> take into account the user's access and authorization levels.</t>
		<figure anchor="fieldSet-id-response-example">
		<name>Example of RDAP Response According to the "id" Field Set</name>
		<sourcecode type="json">
	{	{
	"rdapConformance": [	"rdapConformance": [
	"rdap_level_0",	"rdap_level_0",
	"subsetting"	"subsetting"
	],	],
	...	...
	"domainSearchResults": [	"domainSearchResults": [
	{	{
	"objectClassName": "domain",	"objectClassName": "domain",
	"ldhName": "example1.com",	"ldhName": "example1.com",

	skipping to change at line 225 ¶	skipping to change at line 294 ¶
	"value": "https://example.com/rdap/domain/example2.com",	"value": "https://example.com/rdap/domain/example2.com",
	"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"
	}	}
	]	]
	},	},
	...	...
	]	]
	}	}

	</artwork>	</sourcecode>
	</figure>	</figure>
		</section>
	</section>	<section anchor="negative-answers">
		<name>Negative Answers</name>
	<section anchor="negative-answers" title="Negative Answers">	<t>Each request including an empty or unsupported "fieldSet" value <bcp14>
	<t>Each request including an empty or unsupported "fieldSet" val	MUST</bcp14> produce an HTTP 400 (Bad Request) response code. Optionally, the r
	ue MUST produce an HTTP 400 (Bad Request) response code. Optionally, the respon	esponse <bcp14>MAY</bcp14> include additional information regarding the supporte
	se MAY include additional information regarding the supported field sets in the	d field sets in the HTTP entity body (<xref target="field-set-error"/>).</t>
	HTTP entity body (<xref target="field-set-error"/>).</t>	<figure anchor="field-set-error">
		<name>Example of RDAP Error Response Due to an Invalid Field Set Include
	<figure anchor="field-set-error" title="Example of RDAP error response due	d in the Request</name>
	to an invalid field set included in the request">
	<artwork xml:space="preserve">


		<sourcecode type="json">
	{	{
	"errorCode": 400,	"errorCode": 400,
	"title": "Field set 'unknownfieldset' is not valid",	"title": "Field set 'unknownfieldset' is not valid",
	"description": [	"description": [
	"Supported field sets are: 'afieldset', 'anotherfieldset'."	"Supported field sets are: 'afieldset', 'anotherfieldset'."
	]	]

	}	}

	</artwork>	</sourcecode>
	</figure>	</figure>
	</section>	</section>
		<section anchor="IANA-considerations">
	<section anchor="IANA-considerations" title="IANA Considerations">	<name>IANA Considerations</name>
		<t>IANA has registered the following value in the "RDAP Extensions" regist
	<t>IANA is requested to register the following value in the RDAP Extensio	ry:</t>
	ns Registry:</t>


	<t><list style="none">	<dl spacing="compact">
	<t>Extension identifier: subsetting</t>
	<t>Registry operator: Any</t>
	<t>Published specification: This document.</t>
	<t>Contact: IETF <iesg@ietf.org></t>
	<t>Intended usage: This extension describes best practice for partial resp
	onse provisioning.</t>
	</list></t>


	</section>	<dt>Extension identifier:
		</dt>
		<dd>subsetting
		</dd>


	<section anchor="impl-status" title="Implementation Status">	<dt>Registry operator:
	<t>NOTE: Please remove this section and the reference to RFC 7942 prior to	</dt>
	publication as an RFC.</t>	<dd>Any
		</dd>


	<t>This section records the status of known implementations of the protoco	<dt>Published specification:
	l defined by this specification at the time of posting of this Internet-Draft, a	</dt>
	nd is based on a proposal described in <xref target="RFC7942"/>. The descriptio	<dd>RFC 8982
	n of implementations in this section is intended to assist the IETF in its decis	</dd>
	ion processes in progressing drafts to RFCs. Please note that the listing of an
	y individual implementation here does not imply endorsement by the IETF. Furthe
	rmore, no effort has been spent to verify the information presented here that wa
	s supplied by IETF contributors. This is not intended as, and must not be const
	rued to be, a catalog of available implementations or their features. Readers a
	re advised to note that other implementations may exist.</t>


	<t>According to RFC 7942, "this will allow reviewers and working groups to	<dt>Contact:
	assign due consideration to documents that have the benefit of running code, wh	</dt>
	ich may serve as evidence of valuable experimentation and feedback that have mad	<dd>IETF <iesg@ietf.org>
	e the implemented protocols more mature. It is up to the individual working gro	</dd>
	ups to use this information as they see fit".</t>


	<section anchor="iit-cnr-registro-it" title="IIT-CNR/Registro.it">	<dt>Intended usage:
	<t><list style="none">	</dt>
	<t>Responsible Organization: Institute of Informatics and Telematics of	<dd>This extension describes a best practice for partial response provisioning.
	the National Research Council (IIT-CNR)/Registro.it</t>	</dd>
	<t>Location: https://rdap.pubtest.nic.it/</t>
	<t>Description: This implementation includes support for RDAP queries u
	sing data from .it public test environment.</t>
	<t>Level of Maturity: This is an "alpha" test implementation.</t>
	<t>Coverage: This implementation includes all of the features described
	in this specification.</t>
	<t>Contact Information: Mario Loffredo, mario.loffredo@iit.cnr.it</t>
	</list></t>
	</section>


	<section anchor="apnic" title="APNIC">	</dl>
	<t><list style="none">
	<t>Responsible Organization: Asia-Pacific Network Information Centre</t
	>
	<t>Location: https://github.com/APNIC-net/rdap-rmp-demo/tree/partial-re
	sponse</t>
	<t>Description: A proof-of-concept for RDAP mirroring.</t>
	<t>Level of Maturity: This is a proof-of-concept implementation.</t>
	<t>Coverage: This implementation includes all of the features described
	in this specification.</t>
	<t>Contact Information: Tom Harrison, tomh@apnic.net</t>
	</list></t>
	</section>

	</section>	</section>


	<section anchor="security-considerations" title="Security Considerations">	<section anchor="security-considerations">
	<t>A search query typically requires more server resources (such as memory	<name>Security Considerations</name>
	, CPU cycles, and network bandwidth) when compared to a lookup query. This incr	<t>A search query typically requires more server resources (such as memory
	eases the risk of server resource exhaustion and subsequent denial of service.	, CPU cycles, and network bandwidth) when compared to a lookup query. This incr
	This risk can be mitigated by supporting the return of partial responses combine	eases the risk of server resource exhaustion and subsequent denial of service.
	d with other strategies (e.g. restricting search functionality, limiting the rat	This risk can be mitigated by supporting the return of partial responses combine
	e of search requests, and truncating and paging results).</t>	d with other strategies (e.g., restricting search functionality, limiting the ra
		te of search requests, and truncating and paging results).</t>
	<t>Support for partial responses gives RDAP operators the ability to imple ment data access control policies based on the HTTP authentication mechanisms de scribed in <xref target="RFC7481"/>. RDAP operators can vary the information re turned in RDAP responses based on a client's access and authorization levels. F or example:</t>	<t>Support for partial responses gives RDAP operators the ability to imple ment data access control policies based on the HTTP authentication mechanisms de scribed in <xref target="RFC7481"/>. RDAP operators can vary the information re turned in RDAP responses based on a client's access and authorization levels. F or example:</t>

		<ul>
	<t><list style="symbols">	<li>
	<t>the list of fields for each set can differ based on the client's acc	<t>the list of fields for each set can differ based on the client's ac
	ess and authorization levels;<vspace blankLines='1' /></t>	cess and authorization levels;</t>
	<t>the set of available field sets could be restricted based on the cli	<t/>
	ent's access and authorization levels.</t>	</li>
	</list></t>	<li>the set of available field sets could be restricted based on the cli
		ent's access and authorization levels.</li>
		</ul>
	<t>Servers can also define different result limits according to the availa ble field sets, so a more flexible truncation strategy can be implemented. The new query parameter presented in this document provides RDAP operators with a wa y to implement a server that reduces inefficiency risks.</t>	<t>Servers can also define different result limits according to the availa ble field sets, so a more flexible truncation strategy can be implemented. The new query parameter presented in this document provides RDAP operators with a wa y to implement a server that reduces inefficiency risks.</t>

	</section>	</section>

	</middle>	</middle>
	<back>	<back>

	<references title="Normative References">	<references>
	&RFC2119;	<name>References</name>
	&RFC5890;	<references>
	&RFC7230;	<name>Normative References</name>
	&RFC7480;	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R
	&RFC7481;	FC.2119.xml"/>
	&RFC7482;	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R
	&RFC7483;	FC.5890.xml"/>
	&RFC7942;	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R
	&RFC8174;	FC.7230.xml"/>
	&RFC8288;	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R
	</references>	FC.7480.xml"/>
		<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R
		FC.7481.xml"/>
		<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R
		FC.7482.xml"/>
		<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R
		FC.7483.xml"/>


	<references title="Informative References">	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R
	<reference anchor='CQL' target='https://github.com/gregwhitaker/catnap/wiki/	FC.8174.xml"/>
	Catnap-Query-Language-Reference'>	<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.R
	<front>	FC.8288.xml"/>
	<title>Catnap Query Language Reference</title>	</references>
	<author initials='G.' surname='Whitaker' fullname='Greg Whitaker'	<references>
	>	<name>Informative References</name>
	</author>
	<date year='2017' month='September' />
	</front>
	</reference>
	<reference anchor='HATEOAS' target='https://www.e4developer.com/2018/02/16/h
	ateoas-simple-explanation/'>
	<front>
	<title>HATEOAS - a simple explanation</title>
	<author initials='B.' surname='Jedrzejewski' fullname='Bartosz Je
	drzejewski'>
	</author>
	<date year='2018'/>
	</front>
	</reference>
	<reference anchor='REST' target='http://www.ics.uci.edu/~fielding/pubs/disse
	rtation/fielding_dissertation.pdf'>
	<front>
	<title>Architectural Styles and the Design of Network-based Softw
	are Architectures</title>
	<author initials='R.' surname='Fielding' fullname='Roy Thomas Fie
	lding'>
	<organization>PH.D. DISSERTATION, UNIVERSITY OF CALIFORNIA, IRVI
	NE</organization>
	</author>
	<date year='2000'/>
	</front>
	</reference>
	</references>


	<section anchor="approaches-to-partial-response-implementation" title="Approa	<reference anchor="CQL" target="https://github.com/gregwhitaker/catnap/w
	ches to Partial Response Implementation">	iki/Catnap-Query-Language-Reference">
		<front>
		<title>Catnap Query Language Reference</title>
		<author initials="G." surname="Whitaker" fullname="Greg Whitaker">
		</author>
		<date year="2017" month="September"/>
		</front>
		<refcontent>commit d4f402c</refcontent>
		</reference>


	<t>Looking at the implementation experiences of partial response offered b	<reference anchor="HATEOAS" target="https://www.e4developer.com/2018/02/
	y data providers on the web, two approaches are observed:</t>	16/hateoas-simple-explanation/">
		<front>
		<title>HATEOAS - a simple explanation</title>
		<author initials="B." surname="Jedrzejewski" fullname="Bartosz Jedrz
		ejewski">
		</author>
		<date month="February" year="2018"/>
		</front>
		</reference>


	<t><list style="symbols">	<reference anchor="REST" target="https://www.ics.uci.edu/~fielding/pubs/
	<t>the client explicitly describes the data fields to be returned;<vspa	dissertation/fielding_dissertation.pdf">
	ce blankLines='1' /></t>	<front>
	<t>the client describes a name identifying a server-defined set of data	<title>Architectural Styles and the Design of Network-based Software
	fields.</t>	Architectures</title>
	</list></t>	<author initials="R." surname="Fielding" fullname="Roy Thomas Fieldi
		ng">
		</author>
		<date year="2000"/>
		</front>
		<refcontent>Ph.D. Dissertation, University of California, Irvine</refco
		ntent>


		</reference>
		</references>
		</references>
		<section anchor="approaches-to-partial-response-implementation">
		<name>Approaches to Partial Response Implementation</name>
		<t>Looking at the implementation experiences of partial responses offered
		by data providers on the web, two approaches are observed:</t>
		<ul>
		<li>
		<t>the client explicitly describes the data fields to be returned;</t>
		<t/>
		</li>
		<li>the client describes a name identifying a server-defined set of data
		fields.</li>
		</ul>
	<t>The former is more flexible than the latter because clients can specify all the data fields they need. However, it has some drawbacks:</t>	<t>The former is more flexible than the latter because clients can specify all the data fields they need. However, it has some drawbacks:</t>

		<ul>
		<li>
		<t>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
		that of a JSON object. The presence of arrays and deep nested
		objects complicate both the syntax definition of the query and,
		consequently, the processing required on the server side.</t>
		<t/>
		</li>
		<li>
		<t>Clients need to recognize the returned data structure to avoid
		cases when the requested fields are invalid.</t>
		<t/>
		</li>
		<li>The request of some fields might not match the client's access and
		authorization levels. Clients might request unauthorized fields, and
		servers have to define a strategy for responding such as always
		returning an error response or returning a response that ignores the
		unauthorized fields.</li>
		</ul>
		<section anchor="specific-issues-in-rdap">
		<name>Specific Issues Raised by RDAP</name>
		<t>In addition to those listed above, RDAP responses raise some specific
		issues:</t>
		<ul>
		<li>
		<t>Relevant entity object information is included in a jCard, but
		such information cannot be easily selected because it is split
		into the items of a jagged array.</t>
		<t/>
		</li>
		<li>RDAP responses contain some properties providing service
		information (e.g., rdapConformance, links, notices, remarks, etc.),
		which are not normally selected but are just as important.
		They could be returned anyway but, in this case, the server would
		provide unrequested data.</li>
		</ul>
		<t>It is possible to address these issues. For example, the Catnap
		Query Language <xref target="CQL"/> is a comprehensive expression
		language that can be used to customize the JSON response of a RESTful
		web service. Application of CQL to RDAP responses would explicitly
		identify the output fields that would be acceptable when a few fields
		are requested but it would become very complicated when processing a
		larger number of fields. In the following, two CQL expressions for a
		domain search query are shown (<xref target="cql-example"/>). In the
		first, only objectClassName and ldhName are requested. In the second,
		the fields of a possible WHOIS-like response are listed.</t>
		<figure anchor="cql-example">
		<name>Examples of CQL Expressions for a Domain Search Query</name>


	<t><list style="symbols">	<sourcecode type="http-message"><![CDATA[
	<t>fields have to be declared according to a given syntax. This is a s
	imple task when the data structure of the object is flat, but it is much more di
	fficult when the object has a tree structure like that of a JSON object. The pr
	esence of arrays and deep nested objects complicate both the syntax definition o
	f the query and, consequently, the processing required on the server side;<vspac
	e blankLines='1' /></t>
	<t>clients need to recognize the returned data structure to avoid cases
	when the requested fields are invalid;<vspace blankLines='1' /></t>
	<t>the request of some fields might not match the client's access and a
	uthorization levels. Clients might request unauthorized fields and servers have
	to define a strategy for responding, such as always returning an error response
	or returning a response that ignores the unauthorized fields.</t>
	</list></t>

	<section anchor="specific-issues-in-rdap" title="Specific Issues Raised by RD
	AP">

	<t>In addition to those listed above, RDAP responses raise some specific i
	ssues:</t>

	<t><list style="symbols">
	<t>relevant entity object information is included in a jCard, but such
	information cannot be easily selected because it is split into the items of a ja
	gged array;<vspace blankLines='1' /></t>
	<t>RDAP responses contain some properties providing service information
	(e.g. rdapConformance, links, notices, remarks, etc.) which are not normally se
	lected but they are just as important. They could be returned anyway but, in th
	is case, the server would provide unrequested data.</t>
	</list></t>

	<t>It is possible to address these issues. For example, the Catnap Quer
	y Language <xref target="CQL"/> is a comprehensive expression language that can
	be used to customize the JSON response of a RESTful web service. Application of
	CQL to RDAP responses would explicitly identify the output fields that would be
	acceptable when a few fields are requested but it would become very complicated
	when processing a larger number of fields. In the following, two CQL expressio
	ns for a domain search query are shown (<xref target="cql-example"/>). In the f
	irst, only objectClassName and ldhName are requested. In the second, the fields
	of a possible WHOIS-like response are listed.</t>

	<figure anchor="cql-example" title="Examples of CQL expressions for a doma
	in search query">
	<artwork xml:space="preserve"><![CDATA[

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

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

	]]></artwork>	]]>
	</figure>	</sourcecode>
		</figure>
	<t>The field set approach seems to facilitate RDAP interoperability. Se	<t>The field set approach seems to facilitate RDAP interoperability.
	rvers can define basic field sets which, if known to clients, can increase the p	Servers can define basic field sets that, if known to clients, can
	robability of obtaining a valid response. The usage of field sets makes the que	increase the probability of obtaining a valid response. The usage of
	ry string be less complex. Moreover, the definition of pre-defined sets of fiel	field sets makes the query string less complex. Moreover, the
	ds makes it easier to establish result limits.</t>	definition of predefined sets of fields makes it easier to establish
	<t>Finally, considering that there is no real need for RDAP users to hav	result limits.</t>
	e the maximum flexibility in defining all the possible sets of logically connect	<t>Finally, considering that there is no real need for RDAP users to
	ed fields (e.g. users interested in domains usually need to know the status, the	have the maximum flexibility in defining all the possible sets of
	creation date, and the expiry date of each domain), the field set approach is p	logically connected fields (e.g., users interested in domains usually
	referred.</t>	need to know the status, the creation date, and the expiry date of
		each domain), the field set approach is preferred.</t>
	</section>
	</section>	</section>


	<section title="Acknowledgements" numbered="no">
	<t>The authors would like to acknowledge Scott Hollenbeck, Tom Harrison, K
	arl Heinz Wolf, Jasdip Singh, Patrick Mevzek, Benjamin Kaduk, Roman Danyliw, Mur
	ray Kucherawy, Erik Kline and Robert Wilton for their contribution to this docum
	ent.</t>
	</section>	</section>

		<section numbered="false">
	<section title="Change Log" numbered="no">	<name>Acknowledgements</name>
	<t>	<t>The authors would like to acknowledge <contact fullname="Scott Hollenbe
	<list style="hanging">	ck"/>, <contact fullname="Tom Harrison"/>, <contact fullname="Karl Heinz Wolf"/>
	<t hangText="00:">Initial working group version ported from draft-loff	, <contact fullname="Jasdip Singh"/>, <contact fullname="Patrick Mevzek"/>, <con
	redo-regext-rdap-partial-response-03</t>	tact fullname="Benjamin Kaduk"/>, <contact fullname="Roman Danyliw"/>, <contact
	<t hangText="01:">Removed "FOR DISCUSSION" items. Changed t	fullname="Murray Kucherawy"/>, <contact fullname="Erik Kline"/>, and <contact fu
	he basic field sets from REQUIRED to OPTIONAL. Removed the definition of fields	llname="Robert Wilton"/> for their contribution to this document.</t>
	included in "brief" field set. Provided a more detailed description
	of "subsetting_metadata" structure. Removed some references.</t>
	<t hangText="02:">Added the "Negative Answers" section. Cha
	nged "IANA Considerations" section.</t>
	<t hangText="03:">Added the "unicodeName" field in the id fi
	eldSet when a returned domain or nameserver is an IDN. Added RFC5890 to "N
	ormative References" section.</t>
	<t hangText="04:">Recommended the RDAP providers to include a "se
	lf" link in any field set other than "full". Updated "Ackno
	wledgements" section.</t>
	<t hangText="05:">Moved "Approaches to Partial Response Implement
	ation" section to the appendix.</t>
	<t hangText="06:">Clarified the use of self links in "Basic Field
	Sets" section. Added APNIC to the implementations of the "Implementa
	tion Status" section.</t>
	<t hangText="07:">Changed "only a subset is returned" to &qu
	ot;only a subset of fields in each result object is returned" in the "
	Introduction" section. Moved the "RDAP Conformance" section up i
	n the document. Updated the "Acknowledgements" section.</t>
	<t hangText="08:">Changed the rdapConformance tag "subsetting_lev
	el_0" to "subsetting". Moved <xref target="RFC7942"/> to the &qu
	ot;Normative References".</t>
	<t hangText="09:">Corrected the "rdapConformance" con
	tent in <xref target="fieldSet-id-response-example"/>.</t>
	<t hangText="10:">Corrected the JSON content in <xref target="s
	ubset-link-in-response-example"/>. Clarified the meaning of both context and ta
	rget URIs in a result subset link defined in <xref target="subsetting_links"/>.
	Updated the "Acknowledgements" section.</t>
	<t hangText="11:">Minor pre-AD review edits.</t>
	<t hangText="12:">Additional minor pre-AD review edits.</t>
	<t hangText="13:">Edits due to Gen-ART review: in the first paragrap
	h of <xref target="rdap-path-segment-specification"/> clarified how field sets a
	re defined by a server, in the first sentence of <xref target="negative-answers"
	/> replaced SHOULD with MUST. Other minor edits due to AD review.</t>
	<t hangText="14:">Edits due to IESG review:
	<list style="symbols">
	<t>replaced "fewer data transferred" with "less data trans
	ferred" in the "Introduction" section;</t>
	<t>in the "Subsetting Metadata" section:
	<list style="symbols">
	<t>replaced the phrase "collected in a new data structure" w
	ith the phrase "collected in a new JSON data structure";</t>
	<t>replaced "Members are:" with "The AvailableFieldSet
	object includes the following members:";</t>
	<t>clarified that an RDAP server MUST define only one default field se
	t;</t>
	</list>
	</t>
	<t>clarified the required members of a Link object in the "Represent
	ing Subsetting Links" section;</t>
	<t>rewritten the "Dealing with Relationships" section;</t>
	<t>in the "Basic Field Sets" section:
	<list style="symbols">
	<t>replaced the phrase "include a 'self' link in each field set&
	quot; with the phrase "include a 'links' field indicating the 'self' link r
	elationship";</t>
	<t>replaced the phrase "'unicodeName' field MUST be included&quo
	t; with the phrase "'unicodeName' field MUST additionally be included"
	;</t>
	</list>
	</t>
	<t>in the "Negative Answers" section:
	<list style="symbols">
	<t>replaced the phrase "the response MAY include additional info
	rmation regarding the negative answer" with the phrase "the response M
	AY include additional information regarding the supported field sets";</t>
	<t>added a new example;</t>
	</list>
	</t>
	<t>replaced the phrase "and subsequent denial of service due to a
	buse" with the phrase "and subsequent denial of service" in &quot
	;Security Considerations" section;</t>
	<t>corrected the [REST] reference in the "Informative References&quo
	t; section;</t>
	<t>in "Appendix A":
	<list style="symbols">
	<t>added the phrase " offered by data providers on the web&quot
	; after the phrase "Looking at the implementation experiences of partial re
	sponse";</t>
	<t>replaced the phrase "servers should define a strategy"
	with the phrase "servers have to define a strategy";</t>
	<t>replaced the term "latter approach" with the term &quot
	;field set approach" in the "Appendix A.1" section;</t>
	</list>
	</t>
	<t>updated the "Acknowledgements" section.</t>
	</list></t>
	<t hangText="15:">Minor edit in the "Appendix A.1" section
	;</t>
	<t hangText="16:">Changed a figure containing only an RDAP query int
	o text. Made the RDAP queries uniform. Other minor edits.</t>
	</list>
	</t>
	</section>	</section>


	</back>	</back>
	</rfc>	</rfc>

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