api-catalog: a well-known URI and link relation to help discovery of APIs
draft-ietf-httpapi-api-catalog-06
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft whose latest revision state is "Active".
|
|
|---|---|---|---|
| Author | Kevin Smith | ||
| Last updated | 2024-12-05 (Latest revision 2024-11-25) | ||
| Replaces | draft-smith-api-catalog | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Formats | |||
| Reviews |
ARTART Last Call review
(of
-05)
by Tim Bray
Ready w/nits
|
||
| Additional resources | Mailing list discussion | ||
| Stream | WG state | Submitted to IESG for Publication | |
| Associated WG milestone |
|
||
| Document shepherd | Darrel Miller | ||
| Shepherd write-up | Show Last changed 2024-07-06 | ||
| IESG | IESG state | Approved-announcement to be sent::Revised I-D Needed | |
| Consensus boilerplate | Yes | ||
| Telechat date | (None) | ||
| Responsible AD | Francesca Palombini | ||
| Send notices to | darrel@tavis.ca | ||
| IANA | IANA review state | IANA - Not OK | |
| IANA expert review state | Issues identified | ||
| IANA expert review comments | Additional link relations expert comments after "description" field change from "context" to "target domain" in -06, Section 7.2: "This seems problematic, in that it allows any link on the Internet to assert an API catalogue for a given URI. At the very least some security considerations about consuming such an assertion should be outlined. Furthermore, it's a deviation from the Web Linking specification, which defines a link as involving a context, a target, and a relation type. The relation type definition can't modify this relationship. As such I suspect that this specification isn't defining a link relation per se, it's defining _something else_." |
draft-ietf-httpapi-api-catalog-06
Network Working Group K. Smith
Internet-Draft Vodafone
Intended status: Standards Track 25 November 2024
Expires: 29 May 2025
api-catalog: a well-known URI and link relation to help discovery of
APIs
draft-ietf-httpapi-api-catalog-06
Abstract
This document defines the "api-catalog" well-known URI and link
relation. It is intended to facilitate automated discovery and usage
of the APIs published by a given organisation or individual. A
request to the api-catalog resource will return a document providing
information about, and links to, the publisher's APIs.
About This Document
This note is to be removed before publishing as an RFC.
The latest revision of this draft can be found at https://ietf-wg-
httpapi.github.io/api-catalog/draft-ietf-httpapi-api-catalog.html.
Status information for this document may be found at
https://datatracker.ietf.org/doc/draft-ietf-httpapi-api-catalog/.
Discussion of this document takes place on the Building Blocks for
HTTP APIs Working Group mailing list (mailto:httpapi@ietf.org), which
is archived at https://mailarchive.ietf.org/arch/browse/httpapi/.
Subscribe at https://www.ietf.org/mailman/listinfo/httpapi/.
Source for this draft and an issue tracker can be found at
https://github.com/ietf-wg-httpapi/api-catalog.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
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Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on 29 May 2025.
Copyright Notice
Copyright (c) 2024 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents (https://trustee.ietf.org/
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Please review these documents carefully, as they describe your rights
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provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Goals and non-goals . . . . . . . . . . . . . . . . . . . 3
1.2. Notational Conventions . . . . . . . . . . . . . . . . . 4
2. Using the 'api-catalog' well-known URI . . . . . . . . . . . 4
3. The api-catalog link relation . . . . . . . . . . . . . . . . 5
3.1. Using additional link relations . . . . . . . . . . . . . 5
4. The API Catalog document . . . . . . . . . . . . . . . . . . 6
4.1. Nesting API Catalog links . . . . . . . . . . . . . . . . 7
5. Operational considerations . . . . . . . . . . . . . . . . . 7
5.1. Accounting for APIs distributed across multiple
domains . . . . . . . . . . . . . . . . . . . . . . . . . 7
5.2. Internal use of api-catalog for private APIs . . . . . . 8
5.3. Scalability guidelines . . . . . . . . . . . . . . . . . 9
5.4. Monitoring and maintenance . . . . . . . . . . . . . . . 9
5.5. Integration with existing API management frameworks . . . 10
6. Conformance to RFC8615 . . . . . . . . . . . . . . . . . . . 11
6.1. Path suffix . . . . . . . . . . . . . . . . . . . . . . . 11
6.2. Formats and associated media types . . . . . . . . . . . 11
6.3. Registration of the api-catalog well-known URI . . . . . 11
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
7.1. The api-catalog well-known URI . . . . . . . . . . . . . 12
7.2. The api-catalog link relation . . . . . . . . . . . . . . 12
7.3. The api-catalog Profile URI . . . . . . . . . . . . . . . 12
8. Security Considerations . . . . . . . . . . . . . . . . . . . 13
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 13
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9.1. Normative References . . . . . . . . . . . . . . . . . . 13
9.2. Informative References . . . . . . . . . . . . . . . . . 14
Appendix A. Example API Catalog documents . . . . . . . . . . . 15
A.1. Using Linkset with RFC8615 relations . . . . . . . . . . 15
A.2. Using Linkset with bookmarks . . . . . . . . . . . . . . 17
A.3. Nesting API Catalog links . . . . . . . . . . . . . . . . 18
Appendix B. Acknowledgements . . . . . . . . . . . . . . . . . . 19
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 19
1. Introduction
An organisation or individual may publish Application Programming
Interfaces (APIs) to encourage requests for interaction from external
parties. Such APIs must be discovered before they may be used -
i.e., the external party needs to know what APIs a given publisher
exposes, their purpose, any policies for usage, and the endpoint to
interact with each API. To facilitate automated discovery of this
information, and automated usage of the APIs, this document proposes:
* a well-known URI [WELL-KNOWN], 'api-catalog', encoded as a URI
reference to an API catalog document describing a Publisher's API
endpoints.
* a link relation [WEB-LINKING], 'api-catalog', of which the target
resource is the Publisher's API Catalog document.
1.1. Goals and non-goals
The primary goal is to facilitate the automated discovery of a
Publisher's public API endpoints, along with metadata that describes
the purpose and usage of each API, by specifying a well-known URI
that returns an API catalog document. The API catalog document is
primarily machine-readable to enable automated discovery and usage of
APIs, and it may also include links to human-readable documentation.
Non-goals: this document does not mandate paths for API endpoints.
i.e., it does not mandate that my_example_api's endpoint should be
https://www.example.com/.well-known/api-catalog/my_example_api , nor
even to be hosted at www.example.com (although it is not forbidden to
do so).
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1.2. Notational Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here. These words may also appear in this
document in lower case as plain English words, absent their normative
meanings.
The term "content negotiation" and "status code" are from [HTTP].
The term "well-known URI" is from [WELL-KNOWN]. The term "link
relation" is from [WEB-LINKING].
The term "Publisher" refers to an organisation, company or individual
that publishes one or more APIs for usage by external third parties.
A fictional Publisher named "example" is used throughout this
document. The examples use the FQDNs "www.example.com",
"developer.example.com", "apis.example.com", "apis.example.net",
"gaming.example.com", "iot.example.net",where the use of the .com and
.net TLDs and various subdomains are simply to illustrate that the
"example" Publisher may have their API portfolio distributed across
various domains for which they are the authority. For scenarios
where the Publisher "example" is not the authority for a given
_.example._ domain then that is made explicit in the text.
In this document, "API" means the specification resources required
for an external party (or in the case of 'private' APIs, an internal
party) to implement software which uses the Publisher's Application
Programming Interface.
The specification recommends the use of TLS, hence "HTTPS" and
"https://" are used throughout.
2. Using the 'api-catalog' well-known URI
The api-catalog well-known URI is intended for HTTPS servers that
publish APIs.
* The API Catalog MUST be named "api-catalog" in a well-known
location as described by [WELL-KNOWN].
* The location of the API Catalog document is decided by the
Publisher: the /.well-known/api-catalog URI provides a convenient
reference to that location.
A Publisher supporting this URI:
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* SHALL resolve an HTTPS GET request to /.well-known/api-catalog and
return an API catalog document ( as described in Section 4 ).
* SHOULD resolve an HTTPS HEAD request to /.well-known/api-catalog
with a response including a Link header with the relation(s)
defined in Section 3
3. The api-catalog link relation
This document introduces a new link relation [WEB-LINKING], "api-
catalog". This identifies a target resource that represents a list
of APIs available from the Publisher of the context resource. The
target resource URI may be ./well-known/api-catalog , or any other
URI chosen by the Publisher. For example, the Publisher 'example'
could include the api-catalog link relation in the HTTP header and/or
content payload when responding to a request to
https://www.example.com :
HTTP/1.1 200 OK
Content-Type: text/html; charset=UTF-8
Location: /index.html
Link: </my_api_catalog.json>; rel=api-catalog
Content-Length: 356
<!DOCTYPE HTML>
<html>
<head>
<title>Welcome to Example Publisher</title>
</head>
<body>
<p>
<a href="my_api_catalog.json" rel="api-catalog">
Example Publisher's APIs
</a>
</p>
<p>(remainder of content)</p>
</body>
</html>
3.1. Using additional link relations
* "item" [RFC6573]. When used in an API Catalog document, the
"item" link relation identifies a target resource that represents
an API that is a member of the API Catalog.
* Other link relations may be utilised in an API Catalog to convey
metadata descriptions for API links.
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4. The API Catalog document
The API Catalog is a document listing hyperlinks to a Publisher's
APIs. The Publisher may host this API Catalog document at any URI(s)
they choose. As illustration, the API Catalog document URI of
https://www.example.com/my_api_catalog.json can be requested
directly, or via a request to https://www.example.com/.well-known/
api-catalog, which the Publisher will resolve to
https://www.example.com/my_api_catalog.
The Publisher MUST publish the API Catalog document in the Linkset
format application/linkset+json (section 4.2 of [RFC9264]). In
addition, the Publisher MAY make additional formats available via
content negotiation (section 5.3 of [HTTP]) to their /.well-known/
api-catalog location. A non-exhaustive list of such formats that
support the automated discovery, and machine (and human) usage of a
Publisher's APIs, is listed below.
The API Catalog document MUST include hyperlinks to API endpoints,
and is RECOMMENDED to include useful metadata, such as usage
policies, API version information, links to the OpenAPI Specification
[OAS] definitions for each API, etc.. If the Publisher does not
include these metadata directly in the API Catalog document, they
SHOULD make that metadata available at the API endpoint URIs they
have listed (see Appendix A.2 for an example).
Some suitable API Catalog document formats include:
* A linkset in JSON Document format (section 4.2 of [RFC9264]) of
API endpoints and information to facilitate API usage. The
linkset SHOULD include a profile parameter (section 5 of
[RFC9264]) with a Profile URI [RFC7284] value of 'THIS-RFC-URL' to
indicate the linkset is representing an API Catalog document as
defined above. Appendix A includes example API Catalog documents
based on the linkset format.
* An APIs.json document [APIsjson].
* API bookmarks that represent an API entry-point URI, which may be
followed to discover purpose and usage.
* A RESTDesc semantic description for hypermedia APIs [RESTdesc].
* A Hypertext Application Language document [HAL].
* An extension to the Schema.org WebAPI type [WebAPIext].
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If a Publisher already lists their APIs in a format other than
linkset but wish to utilise the /.well-known/api-catalog URI, then:
* They MUST also implement a linkset with, at minimum, hyperlinks to
API endpoints - see the example of Appendix A.2 in Appendix A.
* They MAY support content negotiation at the /.well-known/api-
catalog URI to allow their existing format to be returned.
4.1. Nesting API Catalog links
An API Catalog may itself contain links to other API Catalogs, by
using the 'api-catalog' relation type for each link. An example of
this is given in Appendix A.3.
5. Operational considerations
5.1. Accounting for APIs distributed across multiple domains
A Publisher ("example") may have their APIs hosted across multiple
domains that they manage: e.g., at www.example.com,
developer.example.com, apis.example.com, apis.example.net etc. They
may also use a third-party API hosting provider which hosts APIs on a
distinct domain.
To account for this scenario, it is RECOMMENDED that:
* The Publisher also publish the api-catalog well-known URI at each
of their API domains e.g. https://apis.example.com/.well-known/
api-catalog, https://developer.example.net/.well-known/api-catalog
etc.
* An HTTPS GET request to any of these URIs returns the same result,
namely, the API Catalog document.
* Since the physical location of the API Catalog document is decided
by the Publisher, and may change, the Publisher choose one of
their instances of /.well-known/api-catalog as a canonical
reference to the location of the latest API Catalog. The
Publisher's other instances of ./well-known/api-catalog SHOULD
redirect to this canonical instance of /.well-known/api-catalog to
ensure the latest API Catalog is returned.
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For example, if the Publisher's primary API portal is
https://apis.example.com, then https://apis.example.com/.well-known/
api-catalog SHOULD resolve to the location of the Publisher's latest
API Catalog document. If the Publisher is also the domain authority
for www.example.net, which also hosts a selection of their APIs, then
a request to https://www.example.net/.well-known/api-catalog SHOULD
redirect to https://apis.example.com/.well-known/api-catalog .
If the Publisher is not the domain authority for www.example.net - or
any third-party domain that hosts any of the Publisher's APIs - then
the Publisher MAY include a link in its own API Catalog to that
third-party domain's API Catalog. For example, the API Catalog
available at https://apis.example.com/.well-known/api-catalog) may
list APIs hosted at apis.example.com and also link to the API Catalog
hosted at https://www.example.net/.well-known/api-catalog using the
"api-catalog" link relation:
{
"linkset": [
{
"anchor": "https://www.example.com/.well-known/api-catalog",
"item": [
{
"href": "https://developer.example.com/apis/foo_api"
},
{
"href": "https://developer.example.com/apis/bar_api"
},
{
"href": "https://developer.example.com/apis/cantona_api"
}
],
"api-catalog": "https://www.example.net/./well-known/api-catalog"
}
]
}
5.2. Internal use of api-catalog for private APIs
A Publisher may wish to use the api-catalog well-known URI on their
internal network, to signpost authorised users (e.g. company
employees) towards internal/private APIs not intended for third-party
use. This scenario may incur additional security considerations, as
noted in Section 8.
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5.3. Scalability guidelines
In cases where a Publisher has a large number of APIs, potentially
deployed across multiple domains, then two challenges may arise:
* Maintaining the catalog entries to ensure they are up to date and
any errors corrected.
* Restricting the catalog size to help reduce network and client-
processing overheads.
In both cases a Publisher may benefit from grouping their APIs,
providing an API Catalog document for each group - and use the main
API Catalog hosted at /.well-known/api-catalog to provide links to
these. For example a Publisher may decide to group their APIs
according to a business category (e.g. 'gaming APIs', 'anti-fraud
APIs' etc.) or a technology category (e.g. ''IOT', 'networks', 'AI'
etc.), or any other criterion. This grouping may already be implicit
where the Publisher has already published their APIs across multiple
domains, e.g. at gaming.example.com, iot.example.net, etc.
Section 4.1 below shows how the API Catalog at /.well-known/api-
catalog can use the api-catalog link relation to point to other API
Catalogs.
The Publisher SHOULD consider caching and compression techniques to
reduce the network overhead of large API Catalogs.
5.4. Monitoring and maintenance
Publishers are RECOMMENDED to follow operational best practice when
hosting API Catalog(s), including but not limited to:
* Health. The Publisher SHOULD monitor availability of the API
Catalog, and consider alternate means to resolve requests to
/.well-known/api-catalog during planned downtime of hosts.
* Performance. Although the performance of APIs listed in an API
Catalog can demand high transactions per second and low-latency
response, the retrieval of the API Catalog itself to discover
those APIs is less likely to incur strict performance demands.
That said, the Publisher SHOULD monitor the response time to
fulfil a request for the API Catalog, and determine any necessary
improvements (as with any other Web resource the Publisher
serves). For large API Catalogs, the Publisher SHOULD consider
the techniques described in Section 5.3.
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* Usage. Since the goal of the api-catalog well-known URI is to
facilitate discovery of APIs, the Publisher may wish to correlate
requests to the /.well-known/api-catalog URI with subsequent
requests to the API URIs listed in the catalog.
* Current data. The Publisher SHOULD include the removal of stale
API entries from the API Catalog as part of their API release
lifecycle. The Publisher MAY decide to include metadata regarding
legacy API versions or deprecated APIs to help users of those APIs
discover up-to-date alternatives.
* Correct metadata. The Publisher SHOULD include human and/or
automated checks for syntax errors in the API Catalog. Automated
checks include format validation (e.g. to ensure valid JSON
syntax) and linting to enforce business rules - such as removing
duplicate entries and ensuring descriptions are correctly named
with valid values. A proofread of the API Catalog as part of the
API release lifecycle is RECOMMENDED to detect any errors in
business grammar (for example, an API entry that is described with
valid syntax, but has been allocated an incorrect or outdated
description.)
* Security best practice, as set out in Section 8
5.5. Integration with existing API management frameworks
A Publisher may already utilise an API management framework to
produce their API portfolio. These frameworks typically include the
publication of API endpoint URIs, deprecation and redirection of
legacy API versions, API usage policies and documentation, etc. The
api-catalog well-known URI and API Catalog document are intended to
complement API management frameworks by facilitating the discovery of
the framework's outputs - API endpoints, usage policies and
documentation - and are not intended to replace any existing API
discovery mechanisms the framework has implemented.
Providers of such frameworks may include the production of an API
Catalog and the publication of the /.well-known/api-catalog URI as a
final pre-release (or post-release) step in the release management
workflow. The following steps are recommended:
If the ./well-known/api-catalog URI has not been published
previously, the framework provider should:
* Collate and check the metadata for each API that will be included
in the API Catalog. This metadata is likely to already exist in
the framework.
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* Determine which metadata to include in the API Catalog, following
the requirements set out in Section 4 and the considerations set
out in Section 5.
* Map the chosen metadata to the format(s) described in Section 4.
Where only the hyperlinks to APIs are to be included in the API
Catalog, then the structure suggested in Appendix A.2 may be
followed. Where possible the API Catalog SHOULD include further
metadata per the guidance in Section 4, in which case the
structure suggested in Appendix A can be utilised and adapted
(ensuring compliance to [RFC9264]) to reflect the nature of the
chosen metadata.
* Publish the /.well-known/api-catalog URI following the guidance
set out in Section 2.
If the ./well-known/api-catalog URI has previously been published,
the framework provider should:
* Include a step in the release management lifecycle to refresh the
API Catalog following any changes in API hyperlinks or published
metadata. This could include placing triggers on certain metadata
fields, so that as they are updated in pre-production on the API
framework, the updates are pushed to a pre-production copy of the
API Catalog to be pushed live when the release is published by the
framework.
6. Conformance to RFC8615
The requirements in section 3 of [WELL-KNOWN] for defining Well-Known
Uniform Resource Identifiers are met as described in the following
sub-sections.
6.1. Path suffix
The api-catalog URI SHALL be appended to the /.well-known/ path-
prefix for "well-known locations".
6.2. Formats and associated media types
A /.well-known/api-catalog location MUST support the Linkset
[RFC9264] format of application/linkset+json, and MAY also support
the other formats via content negotiation.
6.3. Registration of the api-catalog well-known URI
See Section 7 considerations below.
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7. IANA Considerations
7.1. The api-catalog well-known URI
This specification registers the "api-catalog" well-known URI in the
Well-Known URI Registry as defined by [WELL-KNOWN].
* URI suffix: api-catalog
* Change Controller: IETF
* Specification document(s): THIS-RFC
* Status: permanent
7.2. The api-catalog link relation
This specification registers the "api-catalog" link relation by
following the procedures per section 2.1.1.1 of [WEB-LINKING]
* Relation Name: api-catalog
* Description: The link target identifies a catalog of the APIs
published by the owner of the link target domain.
* Reference: THIS-RFC
7.3. The api-catalog Profile URI
This specification registers "THIS-RFC-URL" in the "Profile URIs"
registry according to [RFC7284].
* Profile URI: THIS-RFC-URL
* Common Name: API Catalog
* Description: A profile URI to request or signal a linkset
representing an API Catalog.
* Reference: THIS-RFC
RFC Editor's Note: IANA is kindly requested to replace all instances
of THIS-RFC and THIS-RFC-URL with the actual RFC number/URL once
assigned.
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8. Security Considerations
For all scenarios:
* TLS SHOULD be used, i.e. make /.well-known/api-catalog available
exclusively over HTTPS, to ensure no tampering of the API Catalog.
* The Publisher SHOULD take into account the Security Considerations
from [WELL-KNOWN].
* The Publisher SHOULD perform a security and privacy review of the
API Catalog prior to deployment, to ensure it does not leak
personal, business or other sensitive metadata, nor expose any
vulnerability related to the APIs listed.
* The Publisher SHOULD enforce read-only privileges for external
requests to .well-known/api-catalog, and for internal systems and
roles that monitor the .well-known/api-catalog URI. Write
privileges SHOULD only be granted to roles that perform updates to
the API Catalog and/or the forwarding rewrite rules for the .well-
known/api-catalog URI.
* As with any Web offering, it is RECOMMENDED to apply rate-limiting
measures to help mitigate abuse and prevent Denial-of-Service
attacks on the API Catalog endpoint.
For the public-facing APIs scenario: security teams SHOULD
additionally audit the API Catalog to ensure no APIs intended solely
for internal use have been mistakenly included. For example, a
catalog hosted on https://developer.example.com should not expose
unnecessary metadata about any internal domains (e.g.
https://internal.example.com).
For the internal/private APIs scenario: the Publisher SHOULD take
steps to ensure that appropriate controls - such as CORS policies and
access control lists - are in place to ensure only authorised roles
and systems may access an internal api-catalog well-known URI.
9. References
9.1. Normative References
[HTTP] Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke,
Ed., "HTTP Semantics", STD 97, RFC 9110,
DOI 10.17487/RFC9110, June 2022,
<https://www.rfc-editor.org/rfc/rfc9110>.
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[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/rfc/rfc2119>.
[RFC6573] Amundsen, M., "The Item and Collection Link Relations",
RFC 6573, DOI 10.17487/RFC6573, April 2012,
<https://www.rfc-editor.org/rfc/rfc6573>.
[RFC7284] Lanthaler, M., "The Profile URI Registry", RFC 7284,
DOI 10.17487/RFC7284, June 2014,
<https://www.rfc-editor.org/rfc/rfc7284>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/rfc/rfc8174>.
[RFC9264] Wilde, E. and H. Van de Sompel, "Linkset: Media Types and
a Link Relation Type for Link Sets", RFC 9264,
DOI 10.17487/RFC9264, July 2022,
<https://www.rfc-editor.org/rfc/rfc9264>.
[WEB-LINKING]
Nottingham, M., "Web Linking", RFC 8288,
DOI 10.17487/RFC8288, October 2017,
<https://www.rfc-editor.org/rfc/rfc8288>.
[WELL-KNOWN]
Nottingham, M., "Well-Known Uniform Resource Identifiers
(URIs)", RFC 8615, DOI 10.17487/RFC8615, May 2019,
<https://www.rfc-editor.org/rfc/rfc8615>.
9.2. Informative References
[APIsjson] Kin Lane and Steve Willmott, "APIs.json", 15 September
2020, <http://apisjson.org/format/apisjson_0.16.txt>.
[HAL] Mike Kelly, "JSON Hypertext Application Language", 15
September 2020, <https://datatracker.ietf.org/doc/html/
draft-kelly-json-hal-11>.
[OAS] Darrel Miller, Jeremy Whitlock, Marsh Gardiner, Mike
Ralphson, Ron Ratovsky, and Uri Sarid, "OpenAPI
Specification 3.1.0", 15 February 2021,
<https://spec.openapis.org/oas/latest>.
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[RESTdesc] Ruben Verborgh, Erik Mannens, Rick Van de Walle, and
Thomas Steiner, "RESTdesc", 15 September 2023,
<http://apisjson.org/format/apisjson_0.16.txt>.
[RFC8631] Wilde, E., "Link Relation Types for Web Services",
RFC 8631, DOI 10.17487/RFC8631, July 2019,
<https://www.rfc-editor.org/rfc/rfc8631>.
[WebAPIext]
Mike Ralphson and Nick Evans, "WebAPI type extension", 8
July 2020,
<https://webapi-discovery.github.io/rfcs/rfc0001.html>.
Appendix A. Example API Catalog documents
This section is informative and provides and example of an API
Catalog document using the RECOMMENDED linkset format.
A.1. Using Linkset with RFC8615 relations
This example uses the linkset format [RFC9264], and the following
link relations defined in [RFC8631]:
* "service-desc", used to link to a description of the API that is
primarily intended for machine consumption.
* "service-doc", used to link to API documentation that is primarily
intended for human consumption.
* "service-meta", used to link to additional metadata about the API,
and is primarily intended for machine consumption.
* "status", used to link to the API status (e.g. API "health"
indication etc.) for machine and/or human consumption.
Client request:
GET .well-known/api-catalog HTTP/1.1
Host: example.com
Accept: application/linkset+json
Server response:
HTTP/1.1 200 OK
Date: Mon, 01 Jun 2023 00:00:01 GMT
Server: Apache-Coyote/1.1
Content-Type: application/linkset+json;
profile="THIS-RFC-URL"
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{
"linkset": [
{
"anchor": "https://developer.example.com/apis/foo_api",
"service-desc": [
{
"href": "https://developer.example.com/apis/foo_api/spec",
"type": "application/yaml"
}
],
"status": [
{
"href": "https://developer.example.com/apis/foo_api/status",
"type": "application/json"
}
],
"service-doc": [
{
"href": "https://developer.example.com/apis/foo_api/doc",
"type": "text/html"
}
],
"service-meta": [
{
"href": "https://developer.example.com/apis/foo_api/policies",
"type": "text/xml"
}
]
},
{
"anchor": "https://developer.example.com/apis/bar_api",
"service-desc": [
{
"href": "https://developer.example.com/apis/bar_api/spec",
"type": "application/yaml"
}
],
"status": [
{
"href": "https://developer.example.com/apis/bar_api/status",
"type": "application/json"
}
],
"service-doc": [
{
"href": "https://developer.example.com/apis/bar_api/doc",
"type": "text/plain"
}
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]
},
{
"anchor": "https://apis.example.net/apis/cantona_api",
"service-desc": [
{
"href": "https://apis.example.net/apis/cantona_api/spec",
"type": "text/n3"
}
],
"service-doc": [
{
"href": "https://apis.example.net/apis/cantona_api/doc",
"type": "text/html"
}
]
}
]
}
A.2. Using Linkset with bookmarks
This example also uses the linkset format [RFC9264], listing the API
endpoints in an array of bookmarks. Each link shares the same
context anchor (the well-known URI of the API Catalog) and "item"
[RFC9264] link relation (to indicate they are an item in the
catalog). The intent is that by following a bookmark link, a
machine-client can discover the purpose and usage policy for each
API, hence the document targeted by the bookmark link should support
this.
Client request:
GET .well-known/api-catalog HTTP/1.1
Host: example.com
Accept: application/linkset+json
Server response:
HTTP/1.1 200 OK
Date: Mon, 01 Jun 2023 00:00:01 GMT
Server: Apache-Coyote/1.1
Content-Type: application/linkset+json;
profile="THIS-RFC-URL"
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{ "linkset":
[
{ "anchor": "https://www.example.com/.well-known/api-catalog",
"item": [
{"href": "https://developer.example.com/apis/foo_api"},
{"href": "https://developer.example.com/apis/bar_api"},
{"href": "https://developer.example.com/apis/cantona_api"}
]
}
]
}
A.3. Nesting API Catalog links
In this example, a request to the /.well-known/api-catalog URI
returns an array of links of relation type 'api-catalog'. This can
be useful to Publishers with a large number of APIs, who wish to
group them in smaller catalogs (as described in Section 5.3).
Client request:
GET .well-known/api-catalog HTTP/1.1
Host: example.com
Accept: application/linkset+json
Server response:
HTTP/1.1 200 OK
Date: Mon, 01 Jun 2023 00:00:01 GMT
Server: Apache-Coyote/1.1
Content-Type: application/linkset+json;
profile="THIS-RFC-URL"
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{
"linkset": [
{
"anchor": "https://www.example.com/.well-known/api-catalog",
"api-catalog": [
{
"href": "https://apis.example.com/iot/api-catalog"
},
{
"href": "https://ecommerce.example.com/api-catalog"
},
{
"href": "https://developer.example.com/gaming/api-catalog"
}
]
}
]
}
Appendix B. Acknowledgements
Thanks to Jan Algermissen, Phil Archer, Tim Bray, Ben Bucksch, Sanjay
Dalal, David Dong, Mallory Knodel, Max Maton, Darrel Miller, Mark
Nottingham, Roberto Polli, Joey Salazar, Rich Salz, Herbert Van De
Sompel, Tina Tsou and Erik Wilde for their reviews, suggestions and
support.
Author's Address
Kevin Smith
Vodafone
Email: kevin.smith@vodafone.com
URI: https://www.vodafone.com
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