api-catalog: A well-known URI to help discovery of APIs
draft-smith-api-catalog-01

Internet Engineering Task Force                            K. Smith, Ed.
Internet-Draft                                                  Vodafone
Intended status: Standards Track                             12 May 2023
Expires: 13 November 2023

        api-catalog: A well-known URI to help discovery of APIs
                       draft-smith-api-catalog-01

Abstract

   This document defines the "api-catalog" well-known URI.  It is
   intended to facilitate discovery of the APIs published by a Web host.

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   This Internet-Draft will expire on 13 November 2023.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Goals and non-goals . . . . . . . . . . . . . . . . . . .   2
     1.2.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   2.  Using the 'api-catalog' well-known URI  . . . . . . . . . . .   3
   3.  Associated Media type: the api-catalog linkset  . . . . . . .   3
   4.  Link relations  . . . . . . . . . . . . . . . . . . . . . . .   4
   5.  Conformance to RFC8615  . . . . . . . . . . . . . . . . . . .   4
     5.1.  Path prefix . . . . . . . . . . . . . . . . . . . . . . .   5
     5.2.  Supported URI schemes . . . . . . . . . . . . . . . . . .   5
     5.3.  Registration of the api-catalog well-known URI  . . . . .   5
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
     6.1.  The api-catalog well-known URI  . . . . . . . . . . . . .   5
     6.2.  The api-catalog link relation . . . . . . . . . . . . . .   5
     6.3.  The api-portal link relation  . . . . . . . . . . . . . .   5
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   5
     8.2.  Informative References  . . . . . . . . . . . . . . . . .   6
   Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . .   6
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   A Web host 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 Web host exposes, including their
   purpose, any constraints to use, and the endpoints to interact with
   the APIs.  To faciliate discovery of this information, this document
   proposes a well-known URI, 'api-catalog', as a location where a Web
   host's API endpoints are listed and described.

1.1.  Goals and non-goals

   The primary goal is to facilitate the discovery of both a Web Host's
   public API endpoints, and metadata that informs the potential API
   client of the purpose of each API and any constraints around usage.

   Non-goals: this document does not mandate paths for API endpoints.
   i.e., it does not mandate that my_example_api should be available at
   example.com/.well-known/api-catalog/my_example_api (although it is
   not forbidden to do so).

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1.2.  Requirements Language

   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] when, and only when, they appear in all capitals, as
   shown here.

2.  Using the 'api-catalog' well-known URI

   The api-catalog well-known URI is intended for HTTP(S) servers that
   publish APIs and wish to facilitate their discovery.  Since the
   purpose of the api-catalog well-known URI is to facilitate API
   discovery with minimal prior knowledge, it is recommended that
   /.well-known/api-catalog be hosted at a predictable hostname, i.e.
   www.example.com . It may also be hosted at other hostnames, e.g.
   api.example.com, developer.example.com etc.

   A Web host (example.com) supporting this URI:

   *  SHALL resolve an HTTP(S) GET request to /.well-known/api-catalog
      and return a list of public APIs.

   *  SHOULD resolve an HTTP(S) HEAD request to /.well-known/api-catalog
      with a response including a Link header with the relation(s)
      defined in Section 4.

3.  Associated Media type: the api-catalog linkset

   A request to the api-catalog well-known URI is expected to return a
   set of one or more links, each labelled with a link relation to allow
   machines and humans to decide if, and understand why, to follow them.
   The api-catalog is recommended to consist of:

   *  link(s) to the API gateway(s), or portal(s), of the Web Host, that
      present a public Web page with details of APIs offered,
      documentation, Ts & Cs etc.

   *  links to each API offered by the Web Host.  Ideally each of these
      links will be to an API bookmark, which, if followed, will provide
      further links with information on API endpoints, operations,
      versions, documentation etc.

   [RFC9264] defines the application/linkset+json JSON document format
   for link sets, and is used for the following example:

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   { "linkset":
     [
           { "anchor": "https://example.com/",
             "api-portal": [
                   {"href": "https://developer.example.com/my_portal"}
             ]
           },
           { "anchor": "https://example.com/,
             "https://example.com/relations/api1" : [
                   {"href": "https://developer.example.com/apis/api1"}
             ]
           },
           { "anchor": "https://example.com/,
             "https://example.com/relations/api2" : [
                   {"href": "https://developer.example.com/apis/api2"}
             ]
           },
           { "anchor": "https://example.com/,
             "https://some_standards_org.example.com/relations/some_api" : [
                   {"href": "https://developer.example.com/apis/api3"}
             ]
           },
     ]
   }

                   Figure 1: api-catalog linkset example

4.  Link relations

   (Editor's note: TODO.  Suggested are: "api-catalog", and also "api-
   portal" because it seems likely many implementers will have such a
   portal, hence it makes sense to make that common.  The APIs
   themselves are less likely to be common across implementers and
   should use extensible link relations, providing a URI to their
   definition.  This also applies if the API being linked to is based on
   a standard, in which case the standard body in question should
   declare the URI for the extensible link relation definition, e.g.
   https://some_standards_org.example.com/relations/some_api , and this
   can be used by all implementing hosts of that API)

5.  Conformance to RFC8615

   The requirements in section 3 of [RFC8615] for defining Well-Known
   Uniform Resource Identifiers are met as follows:

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5.1.  Path prefix

   The api-catalog URI SHALL be appended to the /.well-known/ path-
   prefix for "well-known locations".

5.2.  Supported URI schemes

   The api-catalog well-known URI may be used with the HTTP and HTTPS
   URI schemes.

5.3.  Registration of the api-catalog well-known URI

   See Section 6 considerations below.

6.  IANA Considerations

6.1.  The api-catalog well-known URI

   This specification registers the "api-catalog" well-known URI in the
   Well-Known URI Registry as defined by [RFC6415] .

   URI suffix: api-catalog

   Specification document(s): draft-smith-api-catalog-01

   Related information: The "api-catalog" documents obtained from the
   same host using the HTTP and HTTPS protocols (using default ports)
   MUST be identical.

6.2.  The api-catalog link relation

   This specification registers the "api-catalog" link relation by
   following the procedures per section 4.2.2 of [RFC8288] (Editor's
   note: this is TODO).

6.3.  The api-portal link relation

   (Editor's note: if the suggestion above to include this is agreed).

7.  Security Considerations

   TBD

8.  References

8.1.  Normative References

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   [RFC6415]  Hammer-Lahav, E., Ed. and B. Cook, "Web Host Metadata",
              RFC 6415, DOI 10.17487/RFC6415, October 2011,
              <https://www.rfc-editor.org/info/rfc6415>.

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

   [RFC8615]  Nottingham, M., "Well-Known Uniform Resource Identifiers
              (URIs)", RFC 8615, DOI 10.17487/RFC8615, May 2019,
              <https://www.rfc-editor.org/info/rfc8615>.

   [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/info/rfc9264>.

8.2.  Informative References

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

Acknowledgements

   TODO

Author's Address

   Kevin Smith (editor)
   Vodafone
   One Kingdom Street
   London
   W2 6BY
   United Kingdom
   Email: kevin.smith@vodafone.com
   URI:   www.vodafone.com

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