<?xml version="1.0" encoding="UTF-8"?><?rfc compact="yes" ?> <?rfc subcompact="no" ?> <?rfc toc="yes" ?> <?rfc sortrefs="yes" ?> <?rfc symrefs="yes" ?><!DOCTYPE rfc [ <!ENTITY nbsp " "> <!ENTITY zwsp "​"> <!ENTITY nbhy "‑"> <!ENTITY wj "⁠"> ]> <rfccategory="std"ipr="trust200902" docName="draft-ietf-httpapi-linkset-10" number="9264" submissionType="IETF" category="std" consensus="true" tocInclude="true" symRefs="true" sortRefs="true" updates="" obsoletes="" xml:lang="en" version="3" xmlns:xi="http://www.w3.org/2001/XInclude"> <front> <title abbrev="Linkset">Linkset: Media Types and a Link Relation Type for Link Sets</title> <seriesInfo name="RFC" value="9264"/> <author initials="E." surname="Wilde" fullname="Erik Wilde"> <organization>Axway</organization> <address> <email>erik.wilde@dret.net</email><uri>http://dret.net/netdret/</uri></address> </author> <author initials="H." surname="Van de Sompel" fullname="Herbert Van de Sompel"> <organization>Data Archiving and Networked Services</organization> <address> <email>herbert.van.de.sompel@dans.knaw.nl</email> <uri>https://orcid.org/0000-0002-0715-6126</uri> </address> </author> <dateday="5" month="May"month="July" year="2022"/> <area>art</area> <workgroup>httpapi</workgroup> <keyword>Web linking</keyword> <keyword>Typed links</keyword> <keyword>JSON</keyword> <keyword>HTTP</keyword> <abstract> <t>This specification defines two formats andrespectiveassociated media types for representing sets of links asstand-alonestandalone documents. One format isJSON-based,based on JSON, and the other is aligned with the format for representing links in the HTTP "Link" header field. This specification also introduces a link relation type to support the discovery of sets of links.</t> </abstract><note title="Note to Readers"> <t>Please discuss this draft on the "Building Blocks for HTTP APIs" mailing list (<eref target="https://www.ietf.org/mailman/listinfo/httpapi"/>).</t> <t>Online access to all versions and files is available on GitHub (<eref target="https://github.com/ietf-wg-httpapi/linkset"/>).</t> </note></front> <middle> <sectiontitle="Introduction" anchor="introduction">anchor="introduction" numbered="true" toc="default"> <name>Introduction</name> <t>Resources on the Web often use typed Web Links <xref target="RFC8288"/>, eitherembedded(1) embedded in resourcerepresentations,representations -- forexampleexample, using the <link> element for HTMLdocuments,documents orconveyed(2) conveyed in the HTTP "Link" header field for documents of any media type. In some cases, however, providing links in this manner is impractical orimpossibleimpossible, and delivering a set of links as astand-alonestandalone document is preferable.</t> <t>Therefore, this specification defines two formats for representing sets of Web Links and their attributes asstand-alonestandalone documents. One serializes links in the same format as the format used in the HTTPLink"Link" header field, and the other serializes links in JSON. It also defines associated media types to represent sets of links, and the "linkset" relation typethat supportsto support the discovery of any resource that conveys a set of links as astand-alonestandalone document.</t> </section> <sectiontitle="Terminology" anchor="terminology">anchor="terminology" numbered="true" toc="default"> <name>Terminology</name> <t>The key words"MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY","<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"OPTIONAL""<bcp14>OPTIONAL</bcp14>" in this document are to be interpreted as described inBCP 14BCP 14 <xref target="RFC2119"/> <xref target="RFC8174"/> when, and only when, they appear in all capitals, as shown here.</t> <t>This specification uses the terms "link context" and "link target" in the same mannerasthat <xreftarget="RFC8288"/>.</t>target="RFC8288">"Web Linking"</xref> uses them.</t> <t>In the examples provided in this document, links in the HTTP "Link" header field are shown on separate lines in order to improve readability. Note, however, that as per <xreftarget="I-D.ietf-httpbis-semantics" section="5.5"/>,target="RFC9110" section="5.5">"HTTP Semantics"</xref>, line breaks are deprecated in values for HTTP fields; only whitespaces and tabs are supported as separators.</t><!-- <t>Additionally, this specification uses the following terms for types of resources involved in providing links by reference:</t> <t><list style="symbols"> <t>A "linkset resource" is a resource that conveys a set of links. <xref target="linkset-formats"/> defines two representations for a set of links, based on the abstract link model defined in <xref target="RFC8288"/>.</t> <t>An "origin resource" is a resource that participates in one or more links provided by a linkset resource. An origin resource can support discovery of an associated linkset resource by using the relation type defined in <xref target="linkset-link-relation"/>. As such, from the perspective of the origin resource, the links conveyed by the linkset resource are provided by reference.</t> </list></t> --></section> <sectiontitle="Useanchor="use-cases" numbered="true" toc="default"> <name>Use Cases andMotivation" anchor="use-cases">Motivation</name> <t>The following sections describe use cases in which providing links by means of a standalone document instead of in an HTTP "Link" header field or as links embedded in the resource representation is advantageous or necessary.</t> <t>For all scenarios, links could be provided by means of astand-alonestandalone document that is formatted according to the JSON-based serialization, the serialization aligned with the HTTP "Link" field format, or both. The former serialization is motivated by the widespread use of JSON and related tools, which suggests that handling sets of links expressed as JSON documents should be attractive to developers. The latter serialization is provided for compatibility with the existing serialization used in the HTTP "Link" field and to allow the reuse of tools created to handle it.</t> <t>It is important to keep in mind that when providing links by means of a standalone representation, other links can still be provided using other approaches,i.e.i.e., it is possible to combine various mechanisms to convey links.</t> <sectiontitle="Third-Party Links" anchor="third-party">anchor="third-party" numbered="true" toc="default"> <name>Third-Party Links</name> <t>In somecasescases, it is useful that links pertaining to a resource are provided by a server other than the one that hosts the resource. For example, this allows:</t> <ul> <li>Providing links in which the resource is involved not just as a link context but also as a link target, with a different resource being the link context.</li> <li>Providing links pertaining to the resource that the server hosting that resource is not aware of.</li> <li>External management of links pertaining to the resource in a special-purpose link management service.</li> </ul> <t>In such cases, links pertaining to a resource can be provided by another, specific resource. That specific resource may bemanagedmanaged, by the same custodian or by anothercustodiancustodian, as the resource to which the links pertain. For clients intent on consuming links provided in that manner, it would be beneficial if the following conditions were met:</t> <ul> <li>Links are provided in a document that uses a well-defined media type.</li> <li>The resource to which the provided links pertain is able to link to the resource that provides these links using a well-known link relation type.</li> </ul> <t>These requirements are addressed in this specification through the definition of two media types and a link relation type, respectively.</t><!-- <t>In order for the server hosting the resource to provide an up-to-date and complete set of links in which that resource participates, the server would need to obtain the links from the third-party resource, and embed them in the resource's representations prior to responding to a client. Doing so would increase latency and load, which may be unnecessary if a client is not intent on consuming these links. Providing links by means of a standalone document, removes the server-to-server communication and resulting overhead required to obtain links. Instead, the consumer of the resource can decide if they need the additional links as context for the resource and only access the third-party resource that provides the links if they do.</t> --></section> <sectiontitle="Challengesanchor="header-writing" numbered="true" toc="default"> <name>Challenges Writing to the HTTPLink"Link" HeaderField" anchor="header-writing">Field</name> <t>In some cases, it is not straightforward to write links to the HTTP "Link" header field from an application. This can, for example, be the case because not all required link information is available to the application or because the application does not have the capability to directly write HTTP fields. In such cases, providing links by means of a standalone document can be a solution. Making the resource that provides these links discoverable can be achieved by means of a typed link.</t> </section> <sectiontitle="Largeanchor="link-volume" numbered="true" toc="default"> <name>Large Number ofLinks" anchor="link-volume">Links</name> <t>When conveying links in an HTTP "Link" header field, it is possible for the size of the HTTP response fields to become unpredictable. This can be the case when links are determined dynamically in a manner dependent on a range of contextual factors. It is possible to statically configure a web server to correctly handle large HTTP response fields by specifying an upper bound for their size. But when the number of links is unpredictable, estimating a reliable upper bound is challenging.</t> <t><xreftarget="I-D.ietf-httpbis-semantics" section="15">HTTP</xref>target="RFC9110" section="15">"HTTP Semantics"</xref> defines error codes related to excess communication by the user agent ("413Request EntityContent Too Large" and "414Request-URIURI Too Long"), but no specific error codes are defined to indicate that response field content exceeds the upper bound that can be handled by the server and thus has been truncated. As a result, applications takecounter measurescountermeasures aimed at controlling the size of the HTTP "Link" headerfield,field -- forexampleexample, by limiting the links they provide to those with select relation types, thereby limiting the value of the HTTP "Link" header field to clients. Providing links by means of a standalone document overcomes challenges related to the unpredictable (to the web server implementation) nature of the size of HTTP "Link" header fields.</t><!-- <t>In more extreme scenarios it is conceivable that the number of links to be conveyed becomes so large that even a standalone document would become too large. For example, this could be the case for highly interlinked resources and when links are provided in which such resources participates as both link context and link target. In such cases, the links could be delivered incrementally, for example, by means of a paged resource model.</t> --></section> </section> <sectiontitle="Documentanchor="linkset-formats" numbered="true" toc="default"> <name>Document Formats for Sets ofLinks" anchor="linkset-formats">Links</name> <t>This section specifies two document formats to convey a set of links. Both are based on the abstract model specified in <xref target="RFC8288"section="2">Web Linking</xref> thatsection="2">"Web Linking"</xref>, which defines a link as consisting of a "link context", a "link relation type", a "link target", and optional "target attributes":</t> <ul> <li>The format defined in <xref target="linkset-native"/> is nearly identical to the field value of the HTTP "Link" header field as specified in <xref target="RFC8288" section="3"/>.</li> <li>The format defined in <xref target="linkset-json"/> is expressed in <xref target="RFC8259">JSON</xref>.</li> </ul> <t>Links provided in the HTTPLink"Link" header field are intended to be used in the context of an HTTPinteractioninteraction, and contextual information that is available during an interaction is used to correctly interpret them. Links provided in link sets, however, can bere-usedreused outside of an HTTP interaction, when no such contextual information is available. As a result, implementers of link sets should strive to make them self-contained by adhering to the following recommendations.</t> <t>For links provided in the HTTPLink"Link" header field that have no anchor or that use relative references, the URI of the resource that delivers the links provides the contextual information that is needed for their correct interpretation. In order to support use cases where link set documents arere-usedreused outside the context of an HTTP interaction, it isRECOMMENDED<bcp14>RECOMMENDED</bcp14> to make them self-contained by adhering to the following guidelines:</t> <ul> <li>For every link provided in the set of links, explicitly provide the link context using the "anchor" attribute.</li> <li>For the link context ("anchor" attribute) and link target ("href" attribute), use URI references that are not relative references (as defined in <xref target="RFC3986" section="4.1"/>). </li> </ul> <t>If these recommendations are not followed, the interpretation of links in link set documents will depend on which URI is used as the context.</t> <t>For a "title" attribute provided on a link in the HTTPLink header,"Link" header field, the language in which the title is expressed is provided by theContent-Language"Content-Language" header field of the HTTP interaction with the resource that delivers the links. This does not apply to "title" attributes provided for links in link set documents because that would constrain all links in a link set to having a single title language and would not support determining title languages when a link set is used outside of an HTTP interaction. In order to support use cases where link set documents arere-usedreused outside the context of an HTTP interaction, it isRECOMMENDED<bcp14>RECOMMENDED</bcp14> to make them self-contained by using the "title*" attribute instead of the "title" attribute because "title*" allows expressing the title language as part of its value by means of a language tag.WithNote that, in this regard,note thatlanguage tags are matchedcase-insensitivelycase insensitively (see <xref target="RFC5646" section="2.1.1"/>). If this recommendation is not followed, accurately determining the language of titles provided on links in link set documents will not be possible.</t> <t>Note also that <xref target="RFC8288" section="3.3"/> deprecates the "rev" construct that was provided by <xref target="RFC5988"/> as a means to express links with a directionality that is the inverse of direct links that use the "rel" construct. In both serializations for link sets defined here, inverse links may be represented as direct links using the "rel" construct and by switching the roles of the resources involved in the link.</t> <sectiontitle="HTTPanchor="linkset-native" numbered="true" toc="default"> <name>HTTP Link Document Format:application/linkset" anchor="linkset-native">application/linkset</name> <t>This document format is nearly identical to the field value of the HTTP "Link" header field as defined in <xref target="RFC8288" section="3"/>, more specifically by its ABNF <xref target="RFC5234"/> production rule for "Link" and its subsequentones.rules. It differs from the format for field values of the HTTP "Link" header field only in that not only spaces and horizontal tabs are allowed as separators but also newline characters as a means to improve readability for humans. The use of non-ASCII characters in the field value of the HTTP "Link"Headerheader field is notallowed,allowed and as such is also not allowed in "application/linkset" link sets.</t> <t>The assigned media type for this format is "application/linkset".</t> <t>When converting an "application/linkset" document to a field value for the HTTP "Link"header,header field, newline charactersMUST<bcp14>MUST</bcp14> be removed orMUST<bcp14>MUST</bcp14> be replaced bywhite spacewhitespace (SP) in order to comply with <xreftarget="I-D.ietf-httpbis-semantics"target="RFC9110" section="5.5"/>.</t> <t>Implementers of "application/linkset" link sets should strive to make them self-contained by following the recommendations provided in <xref target="linkset-formats"/> regarding their use outside the context of an HTTPinteraction provided in <xref target="linkset-formats"/>.</t>interaction.</t> <t>It should be noted that the "application/linkset" format specified here is different from the "application/link-format" format specified in <xref target="RFC6690"/> in that the former fully matches the field value of the HTTP "Link" header field as defined in <xref target="RFC8288" section="3"/>, whereas the latter introduces constraints on that definition to meet requirements for Constrained RESTful Environments (CoRE).</t> </section> <sectiontitle="JSONanchor="linkset-json" numbered="true" toc="default"> <name>JSON Document Format:application/linkset+json" anchor="linkset-json">application/linkset+json</name> <t>This document format uses JSON <xref target="RFC8259"/> as the syntax to represent a set of links. The set of links follows the abstract model defined byWeb Linking<xref target="RFC8288" section="2"/>.</t> <t>The assigned media type for this format is "application/linkset+json".</t> <t>In the interests ofinteroperabilityinteroperability, "application/linkset+json" link setsMUST<bcp14>MUST</bcp14> be encoded using UTF-8 as per <xref target="RFC8259" section="8.1"/>.</t> <t>Implementers of "application/linkset+json" link sets should strive to make them self-contained by following the recommendations provided in <xref target="linkset-formats"/> regarding their use outside the context of an HTTPinteraction provided in <xref target="linkset-formats"/>.</t>interaction.</t> <t>The "application/linkset+json" serialization allows forOPTIONAL<bcp14>OPTIONAL</bcp14> support of a JSON-LD serialization. This can be achieved by adding an appropriate context to the "application/linkset+json" serialization using the approach described inSection 6.8. of<xreftarget="W3C.REC-json-ld-20140116"/>.target="W3C.REC-json-ld" section="6.1" relative="#interpreting-json-as-json-ld"/>. Communities of practice can decide which context best meets their application needs. <xref target="appendix-1"/> shows an example of a possible context that, when added to a JSON serialization, allows it to be interpreted as Resource Description Framework (RDF) data <xreftarget="W3C.REC-rdf11-concepts-20140225"/> data.</t>target="W3C.REC-rdf11-concepts"/>.</t> <sectiontitle="Setanchor="linkset-in-json" numbered="true" toc="default"> <name>Set ofLinks" anchor="linkset-in-json">Links</name> <t>In the JSON representation of a set of links:</t> <ul> <li>A set of links is represented in JSON as an objectwhich MUSTthat <bcp14>MUST</bcp14> contain "linkset" as its sole member.</li> <li>The value of the "linkset" member is an array in which a distinct JSON object--- the "link context object" (see <xref target="linkset-json-link-context-object"/>)--- is used to represent links that have the same link context.</li> <li>Even if there is only one link context object, itMUST<bcp14>MUST</bcp14> be wrapped in an array.</li> </ul> </section> <sectiontitle="Linkanchor="linkset-json-link-context-object" numbered="true" toc="default"> <name>Link ContextObject" anchor="linkset-json-link-context-object">Object</name> <t>In the JSONrepresentationrepresentation, one or more links that have the same link context are represented by a JSONobject,object -- the link context object. A link context object adheres to the following rules:</t> <ul> <li>Each link context objectMAY<bcp14>MAY</bcp14> contain an "anchor" member with a value that represents the link context. If present, this valueMUST<bcp14>MUST</bcp14> be a URI reference andSHOULD NOT<bcp14>SHOULD NOT</bcp14> be a relative reference as defined in <xref target="RFC3986" section="4.1"/>.</li> <li><t> For each distinct relation type that the link context has with link targets, a link context objectMUST<bcp14>MUST</bcp14> contain an additional member. The value of this member is an array in which a distinct JSON object--- the "link target object" (see <xref target="linkset-json-link-target-object"/>)- MUST-- <bcp14>MUST</bcp14> be used for each link target for which the relationship with the link context (value of the encompassinganchor"anchor" member) applies. The name of this member expresses the relation type of the link as follows:</t> <ul> <li>For registered relation types (<xref target="RFC8288" section="2.1.1"/>), the name of this member is the registered name of the relation type.</li> <li>For extension relation types (<xref target="RFC8288" section="2.1.2"/>), the name of this member is the URI that uniquely represents the relation type.</li> </ul></li> <li>Even if there is only one link targetobjectobject, itMUST<bcp14>MUST</bcp14> be wrapped in an array.</li> </ul> </section> <sectiontitle="Linkanchor="linkset-json-link-target-object" numbered="true" toc="default"> <name>Link TargetObject" anchor="linkset-json-link-target-object">Object</name> <t>In the JSONrepresentationrepresentation, a link target is represented by a JSONobject,object -- the link target object. A link target object adheres to the following rules:</t> <ul> <li>Each link target objectMUST<bcp14>MUST</bcp14> contain an "href" member with a value that represents the link target. This valueMUST<bcp14>MUST</bcp14> be a URI reference andSHOULD NOT<bcp14>SHOULD NOT</bcp14> be a relative reference as defined in <xref target="RFC3986" section="4.1"/>. Cases where thehref"href" member ispresent,present but no value is provided for it(i.e.(i.e., the resource providing the set of links is the target of the link in the link target object)MUST<bcp14>MUST</bcp14> be handled by providing an "href" member with an empty string as its value ("href": "").</li> <li>In many cases, a link target is further qualified by target attributes. Various types of attributesexistexist, and they are conveyed as additional members of the link target object as detailed in <xref target="json-target-attributes"/>.</li> </ul> <t>The following example of a JSON-serialized set of links represents one link with its core components: link context, link relation type, and link target.</t> <figure> <name>Simple linkset example</name> <sourcecode type="json"><![CDATA[ { "linkset": [ { "anchor": "https://example.net/bar", "next": [ {"href": "https://example.com/foo"} ] } ] }]]> </sourcecode> </figure> <t>The following example of a JSON-serialized set of links represents two links that share a link context and relation type but have different link targets.</t> <figure> <name>Linkset with two links with the same context</name> <sourcecode type="json"><![CDATA[ { "linkset": [ { "anchor": "https://example.net/bar", "item": [ {"href": "https://example.com/foo1"}, {"href": "https://example.com/foo2"} ] } ] }]]> </sourcecode> </figure> <t>The following example shows a set of links that represents two links, each with a different link context, link target, and relation type. One relation type is registered, and the other is an extension relation type.</t> <figure> <name>Linkset with two links with different contexts</name> <sourcecode type="json"><![CDATA[ { "linkset": [ { "anchor": "https://example.net/bar", "next": [ {"href": "https://example.com/foo1"} ] }, { "anchor": "https://example.net/boo", "https://example.com/relations/baz" : [ {"href": "https://example.com/foo2"} ] } ] }]]> </sourcecode> </figure> </section> <sectiontitle="Linkanchor="json-target-attributes" numbered="true" toc="default"> <name>Link TargetAttributes" anchor="json-target-attributes">Attributes</name> <t>A link may be further qualified by target attributes as defined by <xref target="RFC8288"section="2">Web Linking</xref>.section="2"/>. Three types of attributes exist:</t> <ul><li>Serialisation-defined<li>Serialization-defined attributes as described in <xref target="RFC8288"section="3.4.1">Web Linking</xref>.</li>section="3.4.1"></xref>.</li> <li>Extension attributes defined and used by communities as allowed by <xref target="RFC8288" section="3.4.2"/>.</li> <li>Internationalized versions of the "title" attribute as defined by <xref target="RFC8288"/> and of extension attributes allowed by <xref target="RFC8288" section="3.4"/>.</li><!-- <li>Attributes defined by <xref target="I-D.nottingham-link-hint">Link Hints</xref> and the associated HTTP Link Hint Registry.</li> --></ul> <t>The handling of these different types of attributes is described in the sections below.</t> <sectiontitle="Targetanchor="json-target-attributes-existing" numbered="true" toc="default"> <name>Target Attributes Defined by WebLinking" anchor="json-target-attributes-existing">Linking</name> <t><xref target="RFC8288" section="3.4.1"/> defines the following target attributes that may be used to annotate links: "hreflang", "media", "title", "title*", and "type"; these target attributes follow different occurrence and value patterns. In the JSON representation, these attributesMUST<bcp14>MUST</bcp14> be conveyed as additional members of the link target object as follows:</t><ul> <li>"hreflang": The<dl spacing="normal"> <dt>"hreflang":</dt><dd>The "hreflang" target attribute, defined as optional and repeatable by <xref target="RFC8288"/>,MUST<bcp14>MUST</bcp14> be represented by an "hreflang" member,andits valueMUST<bcp14>MUST</bcp14> be an array (even if thereonlyis only one value to be represented), and each value in that arrayMUST<bcp14>MUST</bcp14> be a string--- representing one value of the "hreflang" target attribute for a link- which-- that follows the same model asinthe syntax discussed in <xreftarget="RFC8288"/> syntax.</li> <li>"media": Thetarget="RFC8288"/>.</dd> <dt>"media":</dt><dd>The "media" target attribute, defined as optional and not repeatable by <xref target="RFC8288"/>,MUST<bcp14>MUST</bcp14> be represented by a "media" member in the link target object, and its valueMUST<bcp14>MUST</bcp14> be a string that follows the same model asin the <xref target="RFC8288"/> syntax.</li> <li>"type": The "type" target attribute, defined as optional and not repeatable by <xref target="RFC8288"/>, MUST be represented by a "type" member inthelink target object, and its value MUST be a string that follows the same model assyntax discussed inthe<xreftarget="RFC8288"/> syntax.</li> <li>"title": Thetarget="RFC8288"/>.</dd> <dt>"title":</dt><dd>The "title" target attribute, defined as optional and not repeatable by <xref target="RFC8288"/>,MUST<bcp14>MUST</bcp14> be represented by a "title" member in the link target object, and its valueMUST<bcp14>MUST</bcp14> be a JSONstring.</li> <li>"title*": Thestring.</dd> <dt>"title*":</dt><dd>The "title*" target attribute, defined as optional and not repeatable by <xref target="RFC8288"/>, is motivated by character encoding and language issues and follows the model defined in <xref target="RFC8187"/>. The details of the JSON representation that applies totitle*"title*" are described in <xref target="linkset-json-i18n-link-parameter"/>.</li> </ul></dd> <dt>"type":</dt><dd>The "type" target attribute, defined as optional and not repeatable by <xref target="RFC8288"/>, <bcp14>MUST</bcp14> be represented by a "type" member in the link target object, and its value <bcp14>MUST</bcp14> be a string that follows the same model as the syntax discussed in <xref target="RFC8288"/>.</dd> </dl> <t>The following example illustrates how therepeatable"hreflang" (repeatable) target attribute and thenot repeatable"type" (not repeatable) targetattributesattribute are represented in a link target object.</t> <figure> <name>Linkset with "hreflang" and "type" target attributes</name> <sourcecode type="json"><![CDATA[ { "linkset": [ { "anchor": "https://example.net/bar", "next": [ { "href": "https://example.com/foo", "type": "text/html", "hreflang": [ "en" , "de" ] } ] } ] }]]> </sourcecode> </figure> </section> <sectiontitle="Internationalizedanchor="linkset-json-i18n-link-parameter" numbered="true" toc="default"> <name>Internationalized TargetAttributes" anchor="linkset-json-i18n-link-parameter">Attributes</name> <t>In addition to the target attributes described in <xref target="json-target-attributes-existing"/>, <xref target="RFC8288" section="3.4"/> also supports attributes that follow the content model of <xref target="RFC8187"/>. In <xref target="RFC8288"/>, these target attributes are recognizable by the use of a trailing asterisk in the attribute name, such as "title*". The content model of <xref target="RFC8187"/> uses a string-based microsyntax that represents the character encoding, an optional language tag, and the escaped attribute value encoded according to the specified character encoding.</t> <t>The JSON serialization for these target attributesMUST<bcp14>MUST</bcp14> be as follows:</t> <ul> <li>An internationalized target attribute is represented as a member of the link context object with the same name (including the*)"*") as the attribute.</li> <li>The character encoding information as prescribed by <xref target="RFC8187"/> is not preserved; instead, the content of the internationalized attribute is represented as a JSON string.</li> <li>The value of the internationalized target attribute is an array that contains one or more JSON objects. The name of one member of such JSONobjectobjects is"value""value", and its value is the actual content (in its unescaped version) of the internationalized target attribute,i.e.i.e., the value of the attribute from which the encoding and language information are removed. The name of another,optional,optional member of such JSONobjectobjects is"language""language", and its value is the language tag <xref target="RFC5646"/> for the language in which the attribute content is conveyed. </li> </ul> <t>The following example illustrates how the "title*" target attribute as defined by <xref target="RFC8288" section="3.4.1"/> is represented in a link target object.</t> <figure> <name>Linkset with "title" and "title*" target attributes</name> <sourcecode type="json"><![CDATA[ { "linkset": [ { "anchor": "https://example.net/bar", "next": [ { "href": "https://example.com/foo", "type": "text/html", "hreflang": [ "en" , "de" ], "title": "Next chapter", "title*": [ { "value": "nächstes Kapitel" , "language" : "de" } ] } ] } ] }]]> </sourcecode> </figure> <t>The above example assumes that the German title contains an umlaut character (in the originalsyntaxsyntax, it would be encoded as title*=UTF-8'de'n%c3%a4chstes%20Kapitel), which gets encoded in its unescaped form in the JSON representation. ImplementationsMUST<bcp14>MUST</bcp14> properly decode/encode internationalized target attributes that follow the model of <xref target="RFC8187"/> when transcoding between the "application/linkset" format and the "application/linkset+json"formats.</t>format.</t> </section> <sectiontitle="Extensionanchor="json-target-attributes-extension" numbered="true" toc="default"> <name>Extension TargetAttributes" anchor="json-target-attributes-extension">Attributes</name> <t>Extension target attributes (e.g., as listed in <xref target="json-target-attributes-existing"/>) are attributes that are not defined by <xref target="RFC8288" section="3.4.1"/>(as listed in <xref target="json-target-attributes-existing"/>),but are nevertheless used to qualify links. They can be defined by communities in any way deemed necessary, and it is up to them to make sure their usage is understood by target applications. However, lacking standardization, there is no interoperable understanding of these extension attributes. One important consequence is that their cardinality is unknown to generic applications. Therefore, in the JSON serialization, all extension target attributes are treated as repeatable.</t> <t>The JSON serialization for these target attributesMUST<bcp14>MUST</bcp14> be as follows:</t> <ul> <li>An extension target attribute is represented as a member of the link target object with the same name as the attribute, including the*"*" if applicable.</li> <li>The value of an extension attributeMUST<bcp14>MUST</bcp14> be represented by an array, even if thereonlyis only one value to be represented.</li> <li>If the extension target attribute does not have a name with a trailing asterisk, then each value in that arrayMUST<bcp14>MUST</bcp14> be a JSON string that represents one value of the attribute.</li> <li>If the extension attribute has a name with a trailing asterisk (it follows the content model of <xref target="RFC8187"/>), then each value in that arrayMUST<bcp14>MUST</bcp14> be a JSON object. The value of each such JSON objectMUST<bcp14>MUST</bcp14> be structured as described in <xref target="linkset-json-i18n-link-parameter"/>.</li> </ul> <t>The following example shows a link target object with three extension target attributes. The value for each extension target attribute is an array. Thetwofirst two are regular extension target attributes, with the first one ("foo") having only one value and the second one ("bar") having two. The last extension target attribute ("baz*") follows the naming rule of <xref target="RFC8187"/> and therefore is encoded according to the serialization described in <xref target="linkset-json-i18n-link-parameter"/>.</t> <figure> <name>Linkset with extension target attributes</name> <sourcecode type="json"><![CDATA[ { "linkset": [ { "anchor": "https://example.net/bar", "next": [ { "href": "https://example.com/foo", "type": "text/html", "foo": [ "foovalue" ], "bar": [ "barone", "bartwo" ], "baz*": [ { "value": "bazvalue" , "language" : "en" } ] } ] } ] }]]> </sourcecode> </figure> </section><!-- <section title="Target Attributes in the HTTP Link Hints Registry" anchor="json-target-attributes-hints"> <t>In order to augment interoperability regarding target attributes, <xref target="I-D.nottingham-link-hint">Link Hints</xref> defines a registration mechanism for target attributes, an associated HTTP Link Hint Registry, and a set of attributes to initially populate that registry. The initial registry, for example, includes the "allow" attribute that can be used to convey the HTTP methods that are supported to interact with the target resource.</t> <t>The JSON serialization for these target attributes MUST be as follows:</t> <t><list style="symbols"> <t>A Link Hint target attribute is represented as a member of the link context object with the same name of the attribute as registered in the HTTP Link Hint Registry.</t> <t>The value of a Link Hint target attribute MUST adhere to the content model specified for the attribute in the HTTP Link Hint Registry.</t> <t>Internationalization of Link Hint target attributes is not applicable.</t> </list></t> <t>The example shows a link target object with the "Type" attribute defined by <xref target="RFC8187"/> and the "allow" attribute that is registered in the HTTP Link Hint Registry. The registry specifies the content model for this attribute as an array of strings. Therefor, that same content model is used in the "application/linkset+json" serialization of sets of links.</t> <figure> <sourcecode type="json"><![CDATA[ { "linkset": [ { "anchor": "http://example.net/bar", "next": [ { "href": "http://example.com/foo", "type": "text/html", "allow": [ "GET", "POST" ] } ] } ] }]]> </sourcecode> </figure> </section> --></section> <sectiontitle="JSON Extensibility" anchor="json-extensibility">anchor="json-extensibility" numbered="true" toc="default"> <name>JSON Extensibility</name> <t>The WeblinkingLinking model(<xref target="RFC8288"/>)<xref target="RFC8288"/> provides for the use of extension target attributes as discussed in <xref target="json-target-attributes-extension"/>. The use of other forms of extensions isNOT RECOMMENDED.<bcp14>NOT RECOMMENDED</bcp14>. Limiting the JSON format in this way allowsto unambiguouslyunambiguous roundtriptrips between links provided in the HTTP "Link" header field, sets of links serialized according to the "application/linkset" format, and sets of links serialized according to the "application/linkset+json" format. </t> <t>Cases may exist in which the use of extensions other than thoseofdiscussed in <xref target="json-target-attributes-extension"/> may beuseful. Foruseful -- for example, when a link set publisher needs to include descriptive or technical metadata for internal consumption.In caseIf such extensions areusedused, theyMUST NOT<bcp14>MUST NOT</bcp14> change the semantics of the JSON members defined in this specification. Agents that consume JSON linkset documents can safely ignore such extensions.</t> </section> </section> </section> <sectiontitle='The "profile" parameteranchor="profile-attribute" numbered="true" toc="default"> <name>The "profile" Parameter formedia typesMedia Types to Represent Sets ofLinks' anchor="profile-attribute">Links</name> <t>As a means to convey specific constraints or conventions (as per <xref target="RFC6906"/>) that apply to a link set document, the "profile" parameterMAY<bcp14>MAY</bcp14> be used in conjunction with the media types "application/linkset" and "application/linkset+json" as detailed in<xref target="linkset-native"/>Sections <xref target="linkset-native" format="counter"/> and <xreftarget="linkset-json"/>,target="linkset-json" format="counter"/>, respectively. For example, the parameter could be used to indicate that a link set uses a specific, limited set of link relation types.</t> <t>The value of the "profile" parameterMUST<bcp14>MUST</bcp14> be a non-empty list of space-separated URIs, each of which identifies specific constraints or conventions that apply to the link set document. When providing multiple profile URIs, care should be taken that the corresponding profiles are not conflicting. Profile URIsMAY<bcp14>MAY</bcp14> be registered in theIANA Profile URI RegistryIANA's "Profile URIs" registry in the manner specified by <xref target="RFC7284"/>.</t> <t>The presence of a "profile" parameter in conjunction with the "application/linkset" and "application/linkset+json" media types does not change the semantics of a link set. As such, clients with and without knowledge of profile URIs can use the same representation.</t> <t><xref target="profile-parameter-example"/> shows an example of using the "profile" parameter in conjunction with the "application/linkset+json" media type.</t> </section> <sectiontitle='The "linkset"anchor="linkset-link-relation" numbered="true" toc="default"> <name>The "linkset" Relation Type for Linking to a Set ofLinks' anchor="linkset-link-relation">Links</name> <t>The target of a link with the "linkset" relation type provides a set of links, including links in which the resource that is the link context participates.</t> <t>A link with the "linkset" relation typeMAY<bcp14>MAY</bcp14> be provided in the header field and/or the body of a resource's representation. It may also be discovered by other means, such as through client-side information.</t> <t>A resourceMAY<bcp14>MAY</bcp14> provide more than one link with a "linkset" relation type. Multiple such links can refer to the same set of links expressed using different media types, or to different sets of links, potentially provided by different third-party services.</t><!-- <t>The use of a link with the "linkset" relation type does not preclude the provision of links with other relation types, i.e. the resource that is the link context can provide typed links other than a "linkset" link. Therefore, the effective set of links provided by that resource is the union of the links that the resource itself provides, and the links provided by the resource that is the target of the "linkset" link - in which it participates.</t> --><t>The set of links provided by the resource that is the target of a "linkset" link may contain links in which the resource that is the context of the "linkset" link does not participate. User agentsMUST<bcp14>MUST</bcp14> process each link in the link set independently, including processing of the link context and link target, andMAY<bcp14>MAY</bcp14> ignore links from the link set in which the context of the "linkset" link does not participate.</t> <t>A user agent that follows a "linkset" link and obtains links for which anchors and targets are expressed as relative references (as per <xref target="RFC3986" section="4.1"/>)MUST<bcp14>MUST</bcp14> determine what the context is for these links; itSHOULD<bcp14>SHOULD</bcp14> ignore links for which it is unable to unambiguously make that determination.</t> <t>As a means to convey specific constraints or conventions (as per <xref target="RFC6906"/>) that apply to a link set document, the "profile" attributeMAY<bcp14>MAY</bcp14> be used in conjunction with the "linkset" link relation type. For example, the attribute could be used to indicate that a link set uses a specific, limited set of link relation types. The value of the "profile" attributeMUST<bcp14>MUST</bcp14> be a non-empty list of space-separated URIs, each of which identifies specific constraints or conventions that apply to the link set document. Profile URIsMAY<bcp14>MAY</bcp14> be registered in theIANA Profile URI RegistryIANA's "Profile URIs" registry in the manner specified by <xref target="RFC7284"/>. <xref target="profile-attribute-example"/> shows an example of using the "profile" attribute on a link with the "linkset" relation type, making both the link set and the profile(s) to which it complies discoverable.</t><!-- <t>There is no constraint on the target URI of a link with the "linkset" relation type; designing and using these URIs is left to the discretion of implementers.</t> <t>In common scenarios (the origin resource is distinct from the linkset resource), it is essential for linkset representations to make the URI of the origin resource explicit for those links in which the origin resource acts as link context.</t> --> <!-- <t>If an origin resource provides a "linkset" link pointing at a linkset resource, and that linkset resource provides a "linkset" link in turn, then this latter link points at links pertaining to the linkset resource. This means that in the context of the latter link, the linkset resource is an origin resource. This means that linkset relations are not transitive, and it is up to a client to decide whether they follow chains of "linkset" links or not.</t> --></section> <sectiontitle="Examples" anchor="linkset-link-examples"> <t><xref target="linkset-link-link-format"/>anchor="linkset-link-examples" numbered="true" toc="default"> <name>Examples</name> <t>Sections <xref target="linkset-link-link-format" format="counter"/> and <xreftarget="linkset-link-json-format"/>target="linkset-link-json-format" format="counter"/> show examples whereby a set of links is provided as "application/linkset" and "application/linkset+json" documents, respectively. <xref target="linkset-rel-example"/> illustrates the use of the "linkset" link relation type to support the discovery of sets oflinkslinks, and <xref target="profile-examples"/> shows how to convey profile information pertaining to a link set.</t> <sectiontitle="Setanchor="linkset-link-link-format" numbered="true" toc="default"> <name>Set of Links Provided asapplication/linkset" anchor="linkset-link-link-format">"application/linkset"</name> <t><xref target="Request1"/> shows a client issuing an HTTP GET request against resource <https://example.org/links/resource1>.</t> <figuretitle="Clientanchor="Request1"> <name>Client HTTP GETrequest" anchor="Request1"> <artworkrequest</name> <sourcecode type="http-message"><![CDATA[ GET /links/resource1 HTTP/1.1 Host: example.org ]]></artwork></sourcecode> </figure> <t><xref target="Response1.1"/> shows the response to the GET request of <xref target="Request1"/>. The response contains aContent-Type"Content-Type" header field specifying that the media type of the response is "application/linkset". A set of links, revealing authorship and versioning related to resource <https://example.org/resource1>, is provided in the response body. The HTTP "Link" header field indicates the availability of an alternate representation of the set of links using media type "application/linkset+json".</t> <figuretitle="Responseanchor="Response1.1"> <name>Response to HTTP GET includes a set oflinks" anchor="Response1.1"> <artworklinks</name> <sourcecode type="http-message"><![CDATA[ HTTP/1.1 200 OK Date: Mon, 12 Aug 2019 10:35:51 GMT Server: Apache-Coyote/1.1 Content-Length: 1023 Content-Type: application/linkset Link: <https://example.org/links/resource1> ; rel="alternate" ; type="application/linkset+json" <https://authors.example.net/johndoe> ; rel="author" ; type="application/rdf+xml" ; anchor="https://example.org/resource1", <https://example.org/resource1?version=3> ; rel="latest-version" ; type="text/html" ; anchor="https://example.org/resource1", <https://example.org/resource1?version=2> ; rel="predecessor-version" ; type="text/html" ; anchor="https://example.org/resource1?version=3", <https://example.org/resource1?version=1> ; rel="predecessor-version" ; type="text/html" ; anchor="https://example.org/resource1?version=2", <https://example.org/resource1?version=1> ; rel="memento" ; type="text/html" ; datetime="Thu, 13 Jun 2019 09:34:33 GMT" ; anchor="https://example.org/resource1", <https://example.org/resource1?version=2> ; rel="memento" ; type="text/html" ; datetime="Sun, 21 Jul 2019 12:22:04 GMT" ; anchor="https://example.org/resource1", <https://authors.example.net/alice> ; rel="author" ; anchor="https://example.org/resource1#comment=1" ]]></artwork></sourcecode> </figure> </section> <sectiontitle="Setanchor="linkset-link-json-format" numbered="true" toc="default"> <name>Set of Links Provided asapplication/linkset+json" anchor="linkset-link-json-format">"application/linkset+json"</name> <t><xref target="Request4"/> shows the client issuing an HTTP GET request against <https://example.org/links/resource1>. In the request, the client uses an "Accept" header field to indicate that it prefers a response in the "application/linkset+json" format.</t> <figuretitle="Clientanchor="Request4"> <name>Client HTTP GET request expressing preference for"application/linkset+json" response" anchor="Request4"> <artworkan "application&wj;/linkset+json" response</name> <sourcecode type="http-message"><![CDATA[ GET links/resource1 HTTP/1.1 Host: example.org Accept: application/linkset+json]]></artwork>]]> </sourcecode> </figure> <t><xref target="Response4.1"/> shows the response to the HTTP GET request of <xref target="Request4"/>. The set of links is serialized according to the media type "application/linkset+json".</t> <figuretitle="Responseanchor="Response4.1"> <name>Response to theclient'sclient's request for theset of links" anchor="Response4.1"> <artworklinkset</name> <sourcecode type="http-message"><![CDATA[ HTTP/1.1 200 OK Date: Mon, 12 Aug 2019 10:46:22 GMT Server: Apache-Coyote/1.1 Content-Type: application/linkset+json Link: <https://example.org/links/resource1> ; rel="alternate" ; type="application/linkset" Content-Length: 1246 { "linkset": [ { "anchor": "https://example.org/resource1", "author": [ { "href": "https://authors.example.net/johndoe", "type": "application/rdf+xml" } ], "memento": [ { "href": "https://example.org/resource1?version=1", "type": "text/html", "datetime": "Thu, 13 Jun 2019 09:34:33 GMT" }, { "href": "https://example.org/resource1?version=2", "type": "text/html", "datetime": "Sun, 21 Jul 2019 12:22:04 GMT" } ], "latest-version": [ { "href": "https://example.org/resource1?version=3", "type": "text/html" } ] }, { "anchor": "https://example.org/resource1?version=3", "predecessor-version": [ { "href": "https://example.org/resource1?version=2", "type": "text/html" } ] }, { "anchor": "https://example.org/resource1?version=2", "predecessor-version": [ { "href": "https://example.org/resource1?version=1", "type": "text/html" } ] }, { "anchor": "https://example.org/resource1#comment=1", "author": [ { "href": "https://authors.example.net/alice"} ] } ] }]]></artwork></sourcecode> </figure> </section> <sectiontitle="Discoveringanchor="linkset-rel-example" numbered="true" toc="default"> <name>Discovering a Link Set via the "linkset" Link RelationType" anchor="linkset-rel-example">Type</name> <t><xref target="Request3"/> shows a client issuing an HTTP HEAD request against resource <https://example.org/resource1>.</t> <figuretitle="Clientanchor="Request3"> <name>Client HTTP HEADrequest" anchor="Request3"> <artworkrequest</name> <sourcecode type="http-message"><![CDATA[ HEAD resource1 HTTP/1.1 Host: example.org ]]></artwork></sourcecode> </figure> <t><xref target="Response3.1"/> shows the response to the HEAD request of <xref target="Request3"/>. The response contains an HTTP "Link" header field with a link that has the "linkset" relation type. It indicates that a set of links is provided by resource <https://example.org/links/resource1>, which provides a representation with media type "application/linkset+json".</t> <figuretitle="Responseanchor="Response3.1"> <name>Response to HTTP HEADrequest" anchor="Response3.1"> <artworkrequest</name> <sourcecode type="http-message"><![CDATA[ HTTP/1.1 200 OK Date: Mon, 12 Aug 2019 10:45:54 GMT Server: Apache-Coyote/1.1 Link: <https://example.org/links/resource1> ; rel="linkset" ; type="application/linkset+json" Content-Length: 236 Content-Type: text/html;charset=utf-8 ]]></artwork></sourcecode> </figure> </section> <sectiontitle="Linkanchor="profile-examples" numbered="true" toc="default"> <name>Link SetProfiles" anchor="profile-examples">Profiles</name> <t>The examples in this section illustrate the use of the "profile" attribute for a link with the "linkset" link relation type and the "profile" attribute for a link set media type. The examples are inspired by the implementation of link sets by GS1 (the standards body behind many of the world's barcodes).</t> <sectiontitle="Usinganchor="profile-attribute-example" numbered="true" toc="default"> <name>Using a "profile" Attribute with a "linkset"Link" anchor="profile-attribute-example">Link</name> <t><xref target="Request_pr_at"/> shows a client issuing an HTTP HEAD request against trade item 09506000134352 at<https://id.gs1.org/01/9506000134352>.</t><eref target="https://id.gs1.org/01/9506000134352" brackets="angle"/>.</t> <figuretitle="Clientanchor="Request_pr_at"> <name>Client HTTP HEADrequest" anchor="Request_pr_at"> <artworkrequest</name> <sourcecode type="http-message"><![CDATA[ HEAD /01/9506000134352 HTTP/1.1 Host: id.gs1.org]]></artwork>]]> </sourcecode> </figure> <t><xref target="Response_pr_at"/> shows the server's response to the request of <xref target="Request_pr_at"/>, including a "linkset" link with a "profile" attribute that has theProfileprofile URI<https://www.gs1.org/voc/?show=linktypes><eref target="https://www.gs1.org/voc/?show=linktypes" brackets="angle"/> as its value. Dereferencing that URI yields a profile document that lists all the link relation types that a client can expect when requesting the link set made discoverable by the "linkset" link. The link relation types are presented in abbreviated form,e.g.e.g., <gs1:activityIdeas>, whereas the actual link relation type URIs are available as hyperlinks on the abbreviations,e.g. <https://www.gs1.org/voc/activityIdeas>.e.g., <eref target="https://www.gs1.org/voc/activityIdeas" brackets="angle"/>. Forposterityposterity, that profile document was saved in the Internet Archive at<https://web.archive.org/web/20210927160406/https://www.gs1.org/voc/?show=linktypes><eref target="https://web.archive.org/web/20210927160406/https://www.gs1.org/voc/?show=linktypes" brackets="angle"/> on 27 September 2021.</t> <figuretitle="Responseanchor="Response_pr_at"> <name>Response to theclient'sclient's HEADrequestrequest, including a "profile" attribute for the "linkset"link" anchor="Response_pr_at"> <artworklink</name> <sourcecode type="http-message"><![CDATA[ HTTP/1.1 307 Temporary Redirect Date: Mon, 27 Sep 2021 16:03:07 GMT Server: nginx Link:https://id.gs1.org/01/9506000134352?linkType=all<https://id.gs1.org/01/9506000134352?linkType=all> ; rel="linkset" ; type="application/linkset+json" ; profile="https://www.gs1.org/voc/?show=linktypes" Location: https://example.com/risotto-rice-with-mushrooms/ ]]></artwork></sourcecode> </figure> </section> <sectiontitle="Usinganchor="profile-parameter-example" numbered="true" toc="default"> <name>Using a "profile" Parameter with a Link Set MediaType" anchor="profile-parameter-example">Type</name> <t><xref target="Request_pr_par"/> shows a client issuing an HTTP HEAD request against the link set<https://id.gs1.org/01/9506000134352?linkType=all><eref target="https://id.gs1.org/01/9506000134352?linkType=all" brackets="angle"/> that was discovered through the HTTP interactions shown in <xref target="profile-attribute-example"/>.</t> <figuretitle="Clientanchor="Request_pr_par"> <name>Client HTTP HEADrequest" anchor="Request_pr_par"> <artworkrequest</name> <sourcecode type="http-message"><![CDATA[ HEAD /01/9506000134352?linkType=all HTTP/1.1 Host: id.gs1.org]]></artwork>]]> </sourcecode> </figure> <t><xref target="Response_pr_par"/> shows the server's response to the request of <xref target="Request_pr_par"/>. Note the "profile" parameter for theapplication/linkset+json"application/linkset+json" media type, which has as its value the sameProfileprofile URI<https://www.gs1.org/voc/?show=linktypes><eref target="https://www.gs1.org/voc/?show=linktypes" brackets="angle"/> as was used in<xref<xref target="Response_pr_at"/>.</t> <figuretitle="Responseanchor="Response_pr_par"> <name>Response to theclient'sclient's HEADrequestrequest, including a "profile" parameter for the "application/linkset+json" mediatype" anchor="Response_pr_par"> <artworktype</name> <sourcecode type="http-message"><![CDATA[ HTTP/1.1 200 OK Date: Mon, 27 Sep 2021 16:03:33 GMT Server: nginx Content-Type: application/linkset+json; profile="https://www.gs1.org/voc/?show=linktypes" Content-Length: 396]]></artwork>]]> </sourcecode> </figure> </section> <sectiontitle="Usinganchor="profile-link-example" numbered="true" toc="default"> <name>Using a Link with a "profile" Link RelationType" anchor="profile-link-example">Type</name> <t>Note that the response shown in <xref target="Response_pr_par"/> from the link set resource is equivalent to the response shown in <xref target="Response_pr_link"/>, which leverages the "profile" link relation type defined in <xref target="RFC6906"/>.</t> <figuretitle="Responseanchor="Response_pr_link"> <name>Response to theclient'sclient's HEADrequestrequest, including a "profile"link" anchor="Response_pr_link"> <artworklink</name> <sourcecode type="http-message"><![CDATA[ HTTP/1.1 200 OK Date: Mon, 27 Sep 2021 16:03:33 GMT Server: nginx Content-Type: application/linkset+json Link:https://www.gs1.org/voc/?show=linktypes;<https://www.gs1.org/voc/?show=linktypes>; rel="profile" Content-Length: 396]]></artwork>]]> </sourcecode> </figure> <t>A link with a "profile" link relation type as shown in <xref target="Response_pr_link"/> can also be conveyed in the link set document itself. This is illustrated by <xref target="Response_pr_linkset"/>. Following the recommendation that all links in a link set document should have an explicit anchor, such a link has the URI of the link set itself as the anchor and theProfileprofile URI as the target. MultipleProfileprofile URIs are handled by using multiple "href" members.</t> <figuretitle="A Link Setanchor="Response_pr_linkset"> <name>A linkset that declares the profile it complieswithwith, using a "profile"link" anchor="Response_pr_linkset">link</name> <sourcecode type="json"><![CDATA[ { "linkset": [ { "anchor": "https://id.gs1.org/01/9506000134352?linkType=all", "profile": [ {"href": "https://www.gs1.org/voc/?show=linktypes"} ] }, { "anchor": "https://id.gs1.org/01/9506000134352", "https://gs1.org/voc/whatsInTheBox": [ {"href": "https://example.com/en/packContents/GB"} ] } ] }]]> </sourcecode> </figure> </section> </section> </section> <sectiontitle="IANA Considerations" anchor="iana-considerations">anchor="iana-considerations" numbered="true" toc="default"> <name>IANA Considerations</name> <sectiontitle="Linknumbered="true" toc="default"> <name>Link Relation Type:linkset">linkset</name> <t>The link relation type belowshould behas been registered by IANA in theLink"Link RelationType RegistryTypes" registry as per <xref target="RFC8288"section="4.2">Web Linking</xref>:</t> <ul empty="true"> <li>Relation Name: linkset</li> <li>Description: Thesection="4.2"/>:</t> <dl newline="false" spacing="normal"> <dt>Relation Name:</dt><dd>linkset</dd> <dt>Description:</dt><dd>The link target of a link with the "linkset" relation type provides a set of links, including links in which the link context of the linkparticipates.</li> <li>Reference: [[ This document ]]</li> </ul>participates.</dd> <dt>Reference:</dt><dd>RFC 9264</dd> </dl> </section> <sectiontitle="Medianumbered="true" toc="default"> <name>Media Type:application/linkset">application/linkset</name> <t>The Internet media typeapplication/linkset"application/linkset" for a linkset encoded as described in <xref target="linkset-native"/>should behas been registered by IANA in theMedia Type Registry"Media Types" registry as per <xref target="RFC6838"/>.</t><ul empty="true"> <li>Type name: application</li> <li>Subtype name: linkset</li> <li>Required parameters: N/A</li> <li>Optional parameters: profile</li> <li>Encoding considerations: Linksets<dl newline="false" spacing="normal"> <dt>Type name:</dt><dd>application</dd> <dt>Subtype name:</dt><dd>linkset</dd> <dt>Required parameters:</dt><dd>N/A</dd> <dt>Optional parameters:</dt><dd>profile</dd> <dt>Encoding considerations:</dt><dd>Linksets are encoded according to thedefinition ofdefinitions provided in <xref target="RFC8288"/>. The encodingofdiscussed in <xref target="RFC8288"/> is based on the general encoding rulesofspecified by HTTP <xreftarget="I-D.ietf-httpbis-semantics"/>, withtarget="RFC9110"/> and allows specific parameters to be extended by theadditionindication ofallowing indicatingcharacter encoding and languagefor specific parametersas defined by <xreftarget="RFC8187"/>.</li> <li>Security considerations: Thetarget="RFC8187"/>.</dd> <dt>Security considerations:</dt><dd>The security considerations of[[ This document ]] apply.</li> <li>Interoperability considerations: N/A</li> <li>Published specification: [[ This document ]]</li> <li>ApplicationsRFC 9264 apply.</dd> <dt>Interoperability considerations:</dt><dd>N/A</dd> <dt>Published specification:</dt><dd>RFC 9264</dd> <dt>Applications that use this mediatype: Thistype:</dt><dd>This media type is not specific to any application, as it can be used by any application that wants to interchangeweb links.</li> <li><t>Additional information:</t> <ul empty="true"> <li>Magic number(s): N/A</li> <li>File extension(s): ThisWeb Links.</dd> </dl> <dl newline="true" spacing="normal"> <dt>Additional information:</dt> <dd> <dl newline="false" spacing="compact"> <dt>Magic number(s):</dt><dd>N/A</dd> <dt>File extension(s):</dt><dd>This media type does not propose a specificextension.</li> <li>Macintoshextension.</dd> <dt>Macintosh file typecode(s): TEXT</li> </ul> </li> <li>Personcode(s):</dt><dd>TEXT</dd> </dl> </dd> </dl> <dl newline="false" spacing="normal"> <dt>Person & email address to contact for furtherinformation: Erikinformation:</dt><dd>Erik Wilde<erik.wilde@dret.net></li> <li>Intended usage: COMMON</li> <li>Restrictions<erik.wilde@dret.net></dd> <dt>Intended usage:</dt><dd>COMMON</dd> <dt>Restrictions onusage: none</li> <li>Author: Erikusage:</dt><dd>none</dd> <dt>Author:</dt><dd>Erik Wilde<erik.wilde@dret.net></li> <li>Change controller: IETF</li> </ul><erik.wilde@dret.net></dd> <dt>Change controller:</dt><dd>IETF</dd> </dl> </section> <sectiontitle="Medianumbered="true" toc="default"> <name>Media Type:application/linkset+json">application/linkset+json</name> <t>The Internet media typeapplication/linkset+json"application/linkset+json" for a linkset encoded as described in <xref target="linkset-json"/>should behas been registered by IANA in theMedia Type Registry"Media Types" registry as per <xref target="RFC6838"/>.</t><ul empty="true"> <li>Type name: application</li> <li>Subtype name: linkset+json</li> <li>Required parameters: N/A</li> <li>Optional parameters: profile</li> <li>Encoding considerations: The<dl newline="false" spacing="normal"> <dt>Type name:</dt><dd>application</dd> <dt>Subtype name:</dt><dd>linkset+json</dd> <dt>Required parameters:</dt><dd>N/A</dd> <dt>Optional parameters:</dt><dd>profile</dd> <dt>Encoding considerations:</dt><dd>The encoding considerations of <xref target="RFC8259"/>apply</li> <li>Security considerations: Theapply.</dd> <dt>Security considerations:</dt><dd>The security considerations of[[ This document ]] apply.</li> <li>Interoperability considerations: TheRFC 9264 apply.</dd> <dt>Interoperability considerations:</dt><dd>The interoperability considerations of <xref target="RFC8259"/>apply.</li> <li>Published specification: [[ This document ]]</li> <li>Applicationsapply.</dd> <dt>Published specification:</dt><dd>RFC 9264</dd> <dt>Applications that use this mediatype: Thistype:</dt><dd>This media type is not specific to any application, as it can be used by any application that wants to interchangeweb links.</li> <li><t>Additional information:</t> <ul empty="true"> <li>Magic number(s): N/A</li> <li>File extension(s): JSONWeb Links.</dd> </dl> <dl newline="true" spacing="normal"> <dt>Additional information:</dt> <dd> <dl newline="false" spacing="compact"> <dt>Magic number(s):</dt><dd>N/A</dd> <dt>File extension(s):</dt><dd>JSON documents often use ".json" as the file extension, and this media type does not propose a specific extension other than this genericone.</li> <li>Macintoshone.</dd> <dt>Macintosh file typecode(s): TEXT</li> </ul> </li> <li>Personcode(s):</dt><dd>TEXT</dd> </dl> </dd> </dl> <dl newline="false" spacing="normal"> <dt>Person & email address to contact for furtherinformation: Erikinformation:</dt><dd>Erik Wilde<erik.wilde@dret.net></li> <li>Intended usage: COMMON</li> <li>Restrictions<erik.wilde@dret.net></dd> <dt>Intended usage:</dt><dd>COMMON</dd> <dt>Restrictions onusage: none</li> <li>Author: Erikusage:</dt><dd>none</dd> <dt>Author:</dt><dd>Erik Wilde<erik.wilde@dret.net></li> <li>Change controller: IETF</li> </ul><erik.wilde@dret.net></dd> <dt>Change controller:</dt><dd>IETF</dd> </dl> </section> </section> <sectiontitle="Security Considerations" anchor="security-considerations">anchor="security-considerations" numbered="true" toc="default"> <name>Security Considerations</name> <t>The security considerations of <xref target="RFC3986" section="7"/> apply, as well as those of Web Linking <xref target="RFC8288"/> as long as the latter are not specifically discussing the risks of exposing information in HTTP header fields.</t> <t>In general, links may cause information leakage when they expose information (such as URIs) that can be sensitive or private. Links may expose "hidden URIs" that are not supposed to be openlyshared,shared and that may not be sufficiently protected. Ideally, none of the URIs exposed in links should be supposed to be "hidden"; instead, if these URIs are supposed to be limited to certain users, then technical measures should be put in place so that accidentally exposing them does not cause any harm.</t> <t>For the specific mechanisms defined in this specification, two security considerations should be taken into account:</t> <ul> <li>The Web Linking model always has an "implicit context", which is the resource of the HTTP interaction. This original context can be lost or can change when self-contained link representations are moved. Changing the context can change the interpretation of links when they have no explicitanchor,anchor or when they use relative URIs. Applications may choose to ignore links that have no explicit anchor or that use relative URIs when these are exchanged instand-alonestandalone resources.</li> <li>The model introduced in this specification supports"3rd party"third-party links", where one party can provide links that have another party's resource as an anchor. Depending on the link semantics and the application context, it is important to verify that there is sufficient trust in that3rdthird party to allow it to provide these links. Applications may choose to treat3rd partythird-party links differently than cases where a resource and the links for that resource are provided by the same party.</li> </ul> </section> </middle> <back><references title="Normative References"> <xi:include href="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.2119.xml"/><references> <name>References</name> <references> <name>Normative References</name> <xi:includehref="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.3986.xml"/>href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.2119.xml"/> <xi:includehref="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.5234.xml"/>href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.3986.xml"/> <xi:includehref="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.5646.xml"/>href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.5234.xml"/> <xi:includehref="https://xml2rfc.tools.ietf.org/public/rfc/bibxml4/reference.W3C.REC-json-ld-20140116.xml"/> <xi:include href="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.6838.xml"/>href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.5646.xml"/> <reference anchor="W3C.REC-json-ld" target="https://www.w3.org/TR/json-ld/"> <front> <title>JSON-LD 1.1: A JSON-based Serialization for Linked Data</title> <author initials="M." surname="Sporny" fullname="Manu Sporny" role="editor"> <organization/> </author> <author initials="G." surname="Kellogg" fullname="Gregg Kellogg" role="editor"> <organization/> </author> <author initials="M." surname="Lanthaler" fullname="Markus Lanthaler" role="editor"> <organization/> </author> <date month="July" year="2020"/> </front> <refcontent>W3C Recommendation REC-json-ld-20140116</refcontent> </reference> <xi:includehref="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.8174.xml"/>href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.6838.xml"/> <xi:includehref="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.8187.xml"/>href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8174.xml"/> <xi:includehref="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.8259.xml"/>href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8187.xml"/> <xi:includehref="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.8288.xml"/>href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8259.xml"/> <xi:includehref="https://xml2rfc.tools.ietf.org/public/rfc/bibxml3/reference.I-D.ietf-httpbis-semantics.xml"/>href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.8288.xml"/> <!--<xi:include href="https://xml2rfc.tools.ietf.org/public/rfc/bibxml3/reference.I-D.nottingham-link-hint.xml"/>draft-ietf-httpbis-semantics (RFC 9110, pub. 6 June 2022) --><!--<xi:include href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.9110.xml"/> </references> <references> <name>Informative References</name> <referenceanchor="W3C.REC-html401-19991224">anchor="W3C.REC-rdf11-concepts" target="https://www.w3.org/TR/rdf11-concepts/"> <front><title abbrev="Media Queries">Media Queries</title><title>RDF 1.1 Concepts and Abstract Syntax</title> <author initials="R." surname="Cyganiak" fullname="Richard Cyganiak" role="editor"> <organization/> </author> <author initials="D." surname="Wood" fullname="David Wood" role="editor"> <organization/> </author> <authorinitials="F." surname="Rivoal" fullname="Florian Rivoal"/>initials="M." surname="Lanthaler" fullname="Markus Lanthaler" role="editor"> <organization/> </author> <datemonth="June" year="2012"/>month="February" year="2014"/> </front><seriesInfo name="World Wide Web Consortium" value="Recommendation REC-css3-mediaqueries-20120619"/><refcontent>W3C Consortium Recommendation REC-rdf11-concepts</refcontent> </reference>--> </references> <references title="Informative References"> <xi:include href="https://xml2rfc.tools.ietf.org/public/rfc/bibxml4/reference.W3C.REC-rdf11-concepts-20140225.xml"/><xi:includehref="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.5988.xml"/>href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.5988.xml"/> <xi:includehref="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.6690.xml"/>href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.6690.xml"/> <xi:includehref="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.6906.xml"/>href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.6906.xml"/> <xi:includehref="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.7284.xml"/> <xi:include href="https://xml2rfc.tools.ietf.org/public/rfc/bibxml/reference.RFC.7942.xml"/>href="https://xml2rfc.ietf.org/public/rfc/bibxml/reference.RFC.7284.xml"/> <reference anchor="DCMI-TERMS" target="https://www.dublincore.org/specifications/dublin-core/dcmi-terms/"> <front> <title abbrev="DCMI Terms">DCMI Metadata Terms</title><author fullname="Dublin<author> <organization>Dublin Core MetadataInitiative" />Initiative</organization> </author> <date month="January" year="2020"/> </front> </reference> </references> </references> <sectiontitle="JSON-LD Context" anchor="appendix-1">anchor="appendix-1" numbered="true" toc="default"> <name>JSON-LD Context</name> <t>A set of links rendered according to the JSON serialization defined in <xref target="linkset-json"/> can be interpreted as RDF triples by adding a <xreftarget="W3C.REC-json-ld-20140116">JSON-LDtarget="W3C.REC-json-ld">JSON-LD context</xref> that maps the JSON keys to corresponding Linked Data terms. And, as per <xreftarget="W3C.REC-json-ld-20140116"/> <eref target="https://www.w3.org/TR/2014/REC-json-ld-20140116/#interpreting-json-as-json-ld">section 6.8</eref>,target="W3C.REC-json-ld" section="6.1" relative="#interpreting-json-as-json-ld"/>, when delivering a link set that is rendered according to the "application/linkset+json" media type to a user agent, a server can convey the availability of such a JSON-LD context by using a link with the relation type"http://www.w3.org/ns/json-ld#context""<eref target="http://www.w3.org/ns/json-ld#context" brackets="none"/>" in the HTTP "Link"header.</t>header field.</t> <t><xref target="contextlinkrel"/> shows the response to an HTTP GET against the URI of a link set resource and illustrates this approach to support the discovery of a JSON-LDContext. Thecontext. This example is inspired by the GS1 implementation and shows a link set that uses relation types from the GS1 vocabulary at<https://www.gs1.org/voc/><eref target="https://www.gs1.org/voc/" brackets="angle"/> that are expressed as HTTP URIs.</t> <figuretitle="Usinganchor="contextlinkrel"> <name>Using a typed link to support the discovery of a JSON-LDContextcontext for aSet of Links" anchor="contextlinkrel">linkset</name> <artworktype="http-message"><![CDATA[type=""><![CDATA[ HTTP/1.1 200 OK Date: Mon, 11 Oct 2021 10:48:22 GMT Server: Apache-Coyote/1.1 Content-Type: application/linkset+json Link: <https://example.org/contexts/linkset.jsonld> ; rel="http://www.w3.org/ns/json-ld#context" ; type="application/ld+json" Content-Length: 1532 { "linkset": [ { "anchor": "https://id.gs1.org/01/09506000149301", "https://gs1.org/voc/pip": [ { "href": "https://example.com/en/defaultPage", "hreflang": [ "en" ], "type": "text/html", "title": "Product information" }, { "href": "https://example.com/fr/defaultPage", "hreflang": [ "fr" ], "title": "Information produit" } ], "https://gs1.org/voc/whatsInTheBox": [ { "href": "https://example.com/en/packContents/GB", "hreflang": [ "en" ], "title": "What's in the box?" }, { "href": "https://example.com/fr/packContents/FR", "hreflang": [ "fr" ], "title": "Qu'y a-t-il dans la boite?" }, { "href": "https://example.com/fr/packContents/CH", "hreflang": [ "fr" ], "title": "Qu'y a-t-il dans la boite?" } ], "https://gs1.org/voc/relatedVideo": [ { "href": "https://video.example", "hreflang": [ "en", "fr" ], "title*": [ { "value": "See it in action!", "language": "en" }, { "value": "Voyez-le en action!", "language": "fr" } ] } ] } ]} ]]>}]]> </artwork> </figure> <t>In order to obtain the JSON-LDContextcontext conveyed by the server, the user agent issues an HTTP GET against the link target of the link with the"http://www.w3.org/ns/json-ld#context""<eref target="http://www.w3.org/ns/json-ld#context" brackets="none"/>" relation type. The response to this GET is shown in <xref target="jsonld-context"/>. This particular JSON-LD context maps "application/linkset+json" representations of link sets to Dublin CoreTermsterms <xref target="DCMI-TERMS"/>. Note that the "linkset" entry in the JSON-LD context is introduced to support links with the<tt>"linkset"</tt>"linkset" relation type in link sets.</t> <figuretitle="JSON-LD Contextanchor="jsonld-context"> <name>JSON-LD context mapping to Dublin CoreTerms" anchor="jsonld-context"> <artworkterms</name> <sourcecode type="http-message"><![CDATA[ HTTP/1.1 200 OK Content-Type: application/ld+json Content-Length: 658 { "@context": [ { "@version": 1.1, "@vocab": "https://gs1.org/voc/", "anchor": "@id", "href": "@id", "linkset": { "@id": "@graph", "@context": { "linkset": "linkset" } }, "title": { "@id": "http://purl.org/dc/terms/title" }, "title*": { "@id": "http://purl.org/dc/terms/title" }, "type": { "@id": "http://purl.org/dc/terms/format" } }, { "language": "@language", "value": "@value", "hreflang": { "@id": "http://purl.org/dc/terms/language", "@container": "@set" } } ]} ]]> </artwork>}]]> </sourcecode> </figure> <t>Applying the JSON-LD context of <xref target="jsonld-context"/> to the link set of <xref target="contextlinkrel"/> allows transforming the "application/linkset+json" link set to an RDF link set. <xref target="triples"/> shows the latter represented by means of the "text/turtle" RDF serialization.</t> <figuretitle="RDFanchor="triples"> <name>RDF serialization of thelink setlinkset resulting from applying the JSON-LDcontext" anchor="triples">context</name> <artwork><![CDATA[ <https://example.com/en/defaultPage> <http://purl.org/dc/terms/format> "text/html" . <https://example.com/en/defaultPage> <http://purl.org/dc/terms/language> "en" . <https://example.com/en/defaultPage> <http://purl.org/dc/terms/title> "Product information" . <https://example.com/en/packContents/GB> <http://purl.org/dc/terms/language> "en" . <https://example.com/en/packContents/GB> <http://purl.org/dc/terms/title> "What's in the box?" . <https://example.com/fr/defaultPage> <http://purl.org/dc/terms/language> "fr" . <https://example.com/fr/defaultPage> <http://purl.org/dc/terms/title> "Information produit" . <https://example.com/fr/packContents/CH> <http://purl.org/dc/terms/language> "fr" . <https://example.com/fr/packContents/CH> <http://purl.org/dc/terms/title> "Qu'y a-t-il dans la boite?" . <https://example.com/fr/packContents/FR> <http://purl.org/dc/terms/language> "fr" . <https://example.com/fr/packContents/FR> <http://purl.org/dc/terms/title> "Qu'y a-t-il dans la boite?" . <https://id.gs1.org/01/09506000149301> <https://gs1.org/voc/pip> <https://example.com/en/defaultPage> . <https://id.gs1.org/01/09506000149301> <https://gs1.org/voc/pip> <https://example.com/fr/defaultPage> . <https://id.gs1.org/01/09506000149301> <https://gs1.org/voc/relatedVideo> <https://video.example> . <https://id.gs1.org/01/09506000149301> <https://gs1.org/voc/whatsInTheBox> <https://example.com/en/packContents/GB> . <https://id.gs1.org/01/09506000149301> <https://gs1.org/voc/whatsInTheBox> <https://example.com/fr/packContents/CH> . <https://id.gs1.org/01/09506000149301> <https://gs1.org/voc/whatsInTheBox> <https://example.com/fr/packContents/FR> . <https://video.example> <http://purl.org/dc/terms/language> "en" . <https://video.example> <http://purl.org/dc/terms/language> "fr" . <https://video.example> <http://purl.org/dc/terms/title> "See it in action!"@en . <https://video.example> <http://purl.org/dc/terms/title> "Voyez-le en action!"@fr . ]]> </artwork> </figure> </section> <sectiontitle="Implementation Status" anchor="implementation-status" removeInRFC="true"> <t>This section records the status of known implementations of the protocol defined by this specification at the time of posting of this Internet-Draft, and is based on a proposal described in RFC 7942 <xref target="RFC7942"/>. The description of implementations in this section is intended to assist the IETF in its decision processes in progressing drafts to RFCs. Please note that the listing of any individual implementation here does not imply endorsement by the IETF. Furthermore, no effort has been spent to verify 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.</t> <t>According to RFC 7942, "this will allow reviewers and working groups to assign due consideration to documents that have the benefit of running code, which may serve as evidence of valuable experimentation and feedback that have made the implemented protocols more mature. It is up to the individual working groups to use this information as they see fit".</t> <section title="GS1" anchor="implementation-GS1"> <t>GS1 is a provider of identifiers, most famously seen in EAN/UPC barcodes for retail and healthcare products, and manages an ecology of services and standards to leverage them at a global scale. GS1 has indicated that it will fully implement this "linkset" specification as a means to allow requesting and representing links pertaining to products, shipments, assets and locations. The current GS1 Digital Link specification makes an informative reference to version 03 of the "linkset" I-D, mentions the formal adoption of that I-D by the IETF HTTPAPI Working Group, and indicates it being on track to achieve RFC status. The GS1 Digital Link specification adopts the JSON format specified by the I-D and mentions future plans to also support the Link header format as well as their respective media types, neither of which have changed since version 03.</t> </section> <section title="FAIR Signposting Profile" anchor="implementation-signposting"> <t>The FAIR Signposting Profile is a community specification aimed at improving machine navigation of scholarly objects on the web through the use of typed web links pointing at e.g. web resources that are part of a specific object, persistent identifiers for the object and its authors, license information pertaining to the object. The specification encourages the use of Linksets and initial implementations are ongoing, for example, for the open source Dataverse data repository platform that was initiated by Harvard University and is meanwhile used by research institutions, worldwide.</t> </section> <section title="Open Journal Systems (OJS)" anchor="implementation-ojs"> <t>Open Journal Systems (OJS) is an open-source software for the management of peer-reviewed academic journals, and is created by the Public Knowledge Project (PKP), released under the GNU General Public License. Open Journal Systems (OJS) is a journal management and publishing system that has been developed by PKP through its federally funded efforts to expand and improve access to research.</t> <t>The OJS platform has implemented "linkset" support as an alternative way to provide links when there are more than a configured limit (they consider using about 10 as a good default, for testing purpose it is currently set to 8).</t> </section> </section> <section title="Acknowledgements" numbered="false">numbered="false" toc="default"> <name>Acknowledgements</name> <t>Thanks for comments and suggestions provided byPhil Archer, Dominique Guinard, Mark Nottingham, Julian Reschke, Rob Sanderson, Stian Soiland-Reyes, Sarven Capadisli, and Addison Phillips.</t><contact fullname="Phil Archer"/>, <contact fullname="Dominique Guinard"/>, <contact fullname="Mark Nottingham"/>, <contact fullname="Julian Reschke"/>, <contact fullname="Rob Sanderson"/>, <contact fullname="Stian Soiland-Reyes"/>, <contact fullname="Sarven Capadisli"/>, and <contact fullname="Addison Phillips"/>.</t> </section> </back> </rfc>