Web-based protocols often require the discovery of host policy or
metadata, where "host" is not a single resource but the entity
controlling the collection of resources identified by Uniform
Resource Identifiers (URI) with a common URI host [RFC3986].
While web protocols have a wide range of metadata needs, they often
use metadata that is concise, has simple syntax requirements, and can
benefit from storing their metadata in a common location used by
other related protocols.
Because there is no URI or representation available to describe a
host, many of the methods used for associating per-resource metadata
(such as HTTP headers) are not available. This often leads to the
overloading of the root HTTP resource (e.g. 'http://example.com/')
with host metadata that is not specific or relevant to the root
To solve those problems, this memo describes a method for locating
host metadata as well as information about individual resources
controlled by the host -- using an HTTP request to a specific path:
/.well-known/host-meta. This memo also registers the well-known URI
suffixes "host-meta" and 'host-meta.json' (for host-meta information in
JSON format) in the Well-Known URI Registry established by RFC 5785.
The information contained in host-meta consists of properties
(name/value pairs) and web links with relations, using the XRD 1.0
(Extensible Resource Descriptor) XML syntax.
Finally, a new link relation 'lrdd' ("link-based resource
descriptor document") is defined to provide resource-specific
information outside of a resource itself.
Working Group Summary
This document is not the product of an IETF working group.
However, it has received extensive review and discussion in
a wide range of technical forums, including the IETF Applications
Area, WebFinger developer community, OASIS XRI Technical
Committee, and W3C www-talk discussion list. Many discussions
of alternative approaches for obtaining metadata about resources
occurred, and will continue to occur in relation to specific information
required by specific applications and protocols. Host-meta (an HTTP-
based mechanism with a well-known URI) emerged as a effective,
web-scale, solution likely to be applicable in a variety of situations.
Host-meta is a straightforward extension of three existing
technologies: XRD 1.0 from OASIS; Web Linking, popularized
by HTML and Atom (RFC 4287); and Well-Known URIs (RFC 5785).
The host-meta concept and document has been reviewed in multiple
forums. There are existing implementations (experimental, though
operational) by major Internet properties (such as yahoo.com and
gmail.com). The WebFinger community have been actively working
with host-meta for personal web discovery. Host-meta is also being
considered for future enhancements to OpenID and OAuth.
The document is sufficiently clear to enable the development of
multiple interoperable implementations and is suitable for publication
as a Proposed Standard.
The document makes normative reference to the OASIS XRD 1.0
specification, which is considered to be stable.
The document makes normative references to RFC 2818 and
RFC 4627, which are in the downref registry.
The Document Shepherd is James Manger.
The Responsible Area Director is Peter Saint-Andre.
The IANA Expert for the registry in this document is