draft-ietf-core-link-format-09.txt   draft-ietf-core-link-format-10.txt 
CoRE Z. Shelby CoRE Z. Shelby
Internet-Draft Sensinode Internet-Draft Sensinode
Intended status: Standards Track November 16, 2011 Intended status: Standards Track January 13, 2012
Expires: May 19, 2012 Expires: July 16, 2012
CoRE Link Format CoRE Link Format
draft-ietf-core-link-format-09 draft-ietf-core-link-format-10
Abstract Abstract
This document defines Web Linking using a link format for use by This document defines Web Linking using a link format for use by
constrained web servers to describe hosted resources, their constrained web servers to describe hosted resources, their
attributes and other relationships between links. Based on the HTTP attributes and other relationships between links. Based on the HTTP
Link Header format defined in RFC5988, the CoRE Link Format is Link Header format defined in RFC5988, the CoRE Link Format is
carried as a payload and is assigned an Internet media type. A well- carried as a payload and is assigned an Internet media type. A well-
known URI is defined as a default entry-point for requesting the known URI is defined as a default entry-point for requesting the
links hosted by a server. links hosted by a server.
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on May 19, 2012. This Internet-Draft will expire on July 16, 2012.
Copyright Notice Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
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2.2. Link relations . . . . . . . . . . . . . . . . . . . . . . 7 2.2. Link relations . . . . . . . . . . . . . . . . . . . . . . 7
2.3. Use of anchors . . . . . . . . . . . . . . . . . . . . . . 8 2.3. Use of anchors . . . . . . . . . . . . . . . . . . . . . . 8
3. CoRE link extensions . . . . . . . . . . . . . . . . . . . . . 8 3. CoRE link extensions . . . . . . . . . . . . . . . . . . . . . 8
3.1. Resource type 'rt' attribute . . . . . . . . . . . . . . . 8 3.1. Resource type 'rt' attribute . . . . . . . . . . . . . . . 8
3.2. Interface description 'if' attribute . . . . . . . . . . . 9 3.2. Interface description 'if' attribute . . . . . . . . . . . 9
3.3. Maximum size estimate 'sz' attribute . . . . . . . . . . . 9 3.3. Maximum size estimate 'sz' attribute . . . . . . . . . . . 9
4. Well-known Interface . . . . . . . . . . . . . . . . . . . . . 9 4. Well-known Interface . . . . . . . . . . . . . . . . . . . . . 9
4.1. Query Filtering . . . . . . . . . . . . . . . . . . . . . 10 4.1. Query Filtering . . . . . . . . . . . . . . . . . . . . . 10
5. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 5. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
6. Security Considerations . . . . . . . . . . . . . . . . . . . 13 6. Security Considerations . . . . . . . . . . . . . . . . . . . 13
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
7.1. Well-known 'core' URI . . . . . . . . . . . . . . . . . . 13 7.1. Well-known 'core' URI . . . . . . . . . . . . . . . . . . 14
7.2. New 'hosts' relation type . . . . . . . . . . . . . . . . 14 7.2. New 'hosts' relation type . . . . . . . . . . . . . . . . 14
7.3. New link-format Internet media type . . . . . . . . . . . 14 7.3. New link-format Internet media type . . . . . . . . . . . 14
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 15 8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 16
9. Changelog . . . . . . . . . . . . . . . . . . . . . . . . . . 16 9. Changelog . . . . . . . . . . . . . . . . . . . . . . . . . . 16
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 18 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 19
10.1. Normative References . . . . . . . . . . . . . . . . . . . 18 10.1. Normative References . . . . . . . . . . . . . . . . . . . 19
10.2. Informative References . . . . . . . . . . . . . . . . . . 18 10.2. Informative References . . . . . . . . . . . . . . . . . . 19
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 19 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 20
1. Introduction 1. Introduction
The Constrained RESTful Environments (CoRE) working group aims at The Constrained RESTful Environments (CoRE) working group aims at
realizing the Representational State Transfer (REST) architecture realizing the Representational State Transfer (REST) architecture
[REST] in a suitable form for the most constrained nodes (e.g. 8-bit [REST] in a suitable form for the most constrained nodes (e.g. 8-bit
microcontrollers with limited memory) and networks (e.g. 6LoWPAN microcontrollers with limited memory) and networks (e.g. 6LoWPAN
[RFC4944]). CoRE is aimed at Machine-to-Machine (M2M) applications [RFC4944]). CoRE is aimed at Machine-to-Machine (M2M) applications
such as smart energy and building automation. such as smart energy and building automation.
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hosted by the server, complemented by attributes about those hosted by the server, complemented by attributes about those
resources and possible further link relations. In CoRE this resources and possible further link relations. In CoRE this
collection of links is carried as a resource of its own (as opposed collection of links is carried as a resource of its own (as opposed
to HTTP headers delivered with a specific resource). This document to HTTP headers delivered with a specific resource). This document
specifies a link format for use in CoRE Resource Discovery by specifies a link format for use in CoRE Resource Discovery by
extending the HTTP Link Header Format [RFC5988] to describe these extending the HTTP Link Header Format [RFC5988] to describe these
link descriptions. The CoRE Link Format is carried as a payload and link descriptions. The CoRE Link Format is carried as a payload and
is assigned an Internet media type. A well-known URI "/.well-known/ is assigned an Internet media type. A well-known URI "/.well-known/
core" is defined as a default entry-point for requesting the list of core" is defined as a default entry-point for requesting the list of
links about resources hosted by a server, and thus performing CoRE links about resources hosted by a server, and thus performing CoRE
Resource Discovery. Resource Discovery. This specification is applicable for use with
CoAP [I-D.ietf-core-coap], HTTP or any other suitable web transfer
protocol. The link format can also be saved in file format.
1.1. Web Linking in CoRE 1.1. Web Linking in CoRE
What is the difference between the CoRE Link Format and [RFC5988]? What is the difference between the CoRE Link Format and [RFC5988]?
Technically the CoRE Link Format is a serialization of a typed link Technically the CoRE Link Format is a serialization of a typed link
as specified in [RFC5988], used to describe relationships between as specified in [RFC5988], used to describe relationships between
resources, so-called "Web Linking". In this specification Web resources, so-called "Web Linking". In this specification Web
Linking is extended with specific constrained M2M attributes, links Linking is extended with specific constrained M2M attributes, links
are carried as a message payload rather than in an HTTP Link Header, are carried as a message payload rather than in an HTTP Link Header,
and a default interface is defined to discover resources hosted by a and a default interface is defined to discover resources hosted by a
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Typical use cases for Web Linking on today's web include e.g. Typical use cases for Web Linking on today's web include e.g.
describing the author of a web page, or describing relations between describing the author of a web page, or describing relations between
web pages (next chapter, previous chapter etc.). Web Linking can web pages (next chapter, previous chapter etc.). Web Linking can
also be applied to M2M applications, where typed links are used to also be applied to M2M applications, where typed links are used to
assist a machine client in finding and understanding how to use assist a machine client in finding and understanding how to use
resources on a server. In this section a few use cases are described resources on a server. In this section a few use cases are described
for how the CoRE Link Format could be used in M2M applications. For for how the CoRE Link Format could be used in M2M applications. For
further technical examples see Section 5. As there are a large range further technical examples see Section 5. As there are a large range
of M2M applications, these use cases are purposely generic. This of M2M applications, these use cases are purposely generic. This
document assumes that different deployments or application domains document assumes that different deployments or application domains
will define the appropriate REST interface descriptions along with will define the appropriate REST Interface Descriptions along with
Resource Types to make discovery meaningful. Resource Types to make discovery meaningful.
1.2.1. Discovery 1.2.1. Discovery
In M2M applications, for example home or building automation, there In M2M applications, for example home or building automation, there
is a need for local clients and servers to find and interact with is a need for local clients and servers to find and interact with
each other without human intervention. The CoRE Link Format can be each other without human intervention. The CoRE Link Format can be
used by servers in such environments to enable Resource Discovery of used by servers in such environments to enable Resource Discovery of
the resources hosted by the server. the resources hosted by the server.
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1.2.2. Resource Collections 1.2.2. Resource Collections
RESTful designs of M2M interfaces often make use of collections of RESTful designs of M2M interfaces often make use of collections of
resources. For example an index of temperature sensors on a data resources. For example an index of temperature sensors on a data
collection node or a list of alarms on a home security controller. collection node or a list of alarms on a home security controller.
The CoRE Link Format can be used to make it possible to find the The CoRE Link Format can be used to make it possible to find the
entry point to a collection and traverse its members. The entry entry point to a collection and traverse its members. The entry
point of a collection would always be included in /.well-known/core point of a collection would always be included in /.well-known/core
to enable its discovery. The members of the collection can be to enable its discovery. The members of the collection can be
defined either through the interface description of the resource defined either through the Interface Description of the resource
along with a parameter resource for the size of the collection, or by along with a parameter resource for the size of the collection, or by
using the link format to describe each resource in the collection. using the link format to describe each resource in the collection.
These links could be located under /.well-known/core or hosted for These links could be located under /.well-known/core or hosted for
example in the root resource of the collection. example in the root resource of the collection.
1.2.3. Resource Directory 1.2.3. Resource Directory
In many deployment scenarios, for example constrained networks with In many deployment scenarios, for example constrained networks with
sleeping servers, or large M2M deployments with bandwidth limited sleeping servers, or large M2M deployments with bandwidth limited
access networks, it makes sense to deploy resource directory entities access networks, it makes sense to deploy resource directory entities
which store links to resources stored on other servers. Think of which store links to resources stored on other servers. Think of
this as a limited search engine for constrained M2M resources. this as a limited search engine for constrained M2M resources.
The CoRE Link Format can be used by a server to register resources The CoRE Link Format can be used by a server to register resources
with a resource directory, or to allow a resource directory to poll with a resource directory, or to allow a resource directory to poll
for resources. Resource polling uses the same process as unicast or for resources. Resource polling uses the same process as unicast or
multicast discovery, however usually without filtering. Resource multicast discovery, however usually without filtering. Resource
registration can be archived by having each server POST their registration can be achieved by having each server POST their
resources to /.well-known/core on the resource directory. This in resources to /.well-known/core on the resource directory. This in
turn adds links to the resource directory under an appropriate turn adds links to the resource directory under an appropriate
resource. These links can then be discovered by any client by a resource. These links can then be discovered by any client by a
performing a GET on the resource directory using a query string performing a GET on the resource directory using a query string
filter. filter.
1.3. Terminology 1.3. Terminology
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
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2.2. Link relations 2.2. Link relations
Since links in the CoRE Link Format are typically used to describe Since links in the CoRE Link Format are typically used to describe
resources hosted by a server, and thus in the absence of the relation resources hosted by a server, and thus in the absence of the relation
parameter the new relation type "hosts" is assumed (see Section 7.2). parameter the new relation type "hosts" is assumed (see Section 7.2).
The "hosts" relation type indicates that the target URI is a resource The "hosts" relation type indicates that the target URI is a resource
hosted by the server given by the base URI, or, if present, the hosted by the server given by the base URI, or, if present, the
anchor parameter. anchor parameter.
To express other relations a links can make use of any registered To express other relations, links can make use of any registered
relation parameter or target attributes by including the relation relation by including the relation parameter. To simplify the
parameter. The context of a relation can be defined using the anchor constrained implementations, the value of a "rel" parameter in this
parameter. In this way, relations between resources hosted on a link format SHOULD NOT contain more than one relation type. There
server, or between hosted resources and external resources can be may be cases where multiple relation types cannot be avoided, for
expressed. example when storing a RFC5988 Link header in this link format. The
context of a relation can be defined using the anchor parameter. In
this way, relations between resources hosted on a server, or between
hosted resources and external resources can be expressed.
2.3. Use of anchors 2.3. Use of anchors
As per Section 5.2 of [RFC5988] a link description MAY include an As per Section 5.2 of [RFC5988] a link description MAY include an
"anchor" attribute, in which case the context is the URI included in "anchor" attribute, in which case the context is the URI included in
that attribute. This is used to describe a relationship between two that attribute. This is used to describe a relationship between two
resources. A consuming implementation can however choose to ignore resources. A consuming implementation can however choose to ignore
such links. It is not expected that all implementations will be able such links. It is not expected that all implementations will be able
to derive useful information from explicitly anchored links. to derive useful information from explicitly anchored links.
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a noun describing the resource. In the case of a temperature a noun describing the resource. In the case of a temperature
resource this could be e.g. an application-specific semantic type resource this could be e.g. an application-specific semantic type
like "OutdoorTemperature", a Universal Resource Name (URN) like like "OutdoorTemperature", a Universal Resource Name (URN) like
"urn:temperature:outdoor" or a URI referencing a specific concept in "urn:temperature:outdoor" or a URI referencing a specific concept in
an ontology like an ontology like
"http://sweet.jpl.nasa.gov/2.0/phys.owl#Temperature". Multiple "http://sweet.jpl.nasa.gov/2.0/phys.owl#Temperature". Multiple
resource type attributes MAY appear in a link. resource type attributes MAY appear in a link.
The resource type attribute is not meant to used to assign a human The resource type attribute is not meant to used to assign a human
readable name to a resource. The "title" attribute defined in readable name to a resource. The "title" attribute defined in
[RFC5988] is meant for that purpose. [RFC5988] is meant for that purpose.
3.2. Interface description 'if' attribute 3.2. Interface description 'if' attribute
The interface description "if" attribute is an opaque string used to The Interface Description "if" attribute is an opaque string used to
provide a name, URI or URN indicating a specific interface definition provide a name, URI or URN indicating a specific interface definition
used to interact with the target resource. One can think of this as used to interact with the target resource. One can think of this as
describing verbs usable on a resource. The interface description describing verbs usable on a resource. The Interface Description
attribute is meant to describe the generic REST interface to interact attribute is meant to describe the generic REST interface to interact
with a resource or a set of resources. It is expected that an with a resource or a set of resources. It is expected that an
interface description will be re-used by different resource types. Interface Description will be re-used by different resource types.
For example the resource types "OutdoorTemperature", "DewPoint" and For example the resource types "OutdoorTemperature", "DewPoint" and
"RelHumidity" could all be accessible using the interface description "RelHumidity" could all be accessible using the Interface Description
"http://www.example.org/myapp.wadl#sensor". "http://www.example.org/myapp.wadl#sensor".
The interface description could be for example the URI of a Web The Interface Description could be for example the URI of a Web
Application Description Language (WADL) [WADL] definition of the Application Description Language (WADL) [WADL] definition of the
target resource "http://www.example.org/myapp.wadl#sensor", a URN target resource "http://www.example.org/myapp.wadl#sensor", a URN
indicating the type of interface to the resource "urn:myapp:sensor", indicating the type of interface to the resource "urn:myapp:sensor",
or an application-specific name "Sensor". Multiple interface or an application-specific name "Sensor". Multiple Interface
description attributes MAY appear in a link. Description attributes MAY appear in a link.
3.3. Maximum size estimate 'sz' attribute 3.3. Maximum size estimate 'sz' attribute
The maximum size estimate attribute "sz" gives an indication of the The maximum size estimate attribute "sz" gives an indication of the
maximum size of the resource indicated by the target URI. This maximum size of the resource indicated by the target URI. This
attribute is not expected to be included for small resources that can attribute is not expected to be included for small resources that can
comfortably by carried in a single Maximum Transmission Unit (MTU), comfortably by carried in a single Maximum Transmission Unit (MTU),
but SHOULD be included for resources larger than that. The maximum but SHOULD be included for resources larger than that. The maximum
size estimate attribute MUST NOT appear more than once in a link. size estimate attribute MUST NOT appear more than once in a link.
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out of scope for this document, and is expected to be specified out of scope for this document, and is expected to be specified
separately. separately.
4.1. Query Filtering 4.1. Query Filtering
A server implementing this document MAY recognize the query part of a A server implementing this document MAY recognize the query part of a
resource discovery URI as a filter on the resources to be returned. resource discovery URI as a filter on the resources to be returned.
The query part should conform to the following syntax. Note that The query part should conform to the following syntax. Note that
this only defines querying for a single parameter at a time. this only defines querying for a single parameter at a time.
filter-query = resource-param "=" query-pattern filter-query = resource-param "=" query-pattern
resource-param = "uri" / parmname resource-param = "uri" / parmname
query-pattern = ptoken [ "*" ] query-pattern = search-token [ "*" ]
ptoken = <Defined in RFC5988> search-token = *search-char
search-char = unreserved / pct-encoded
/ ":" / "@" ; from pchar
/ "/" / "?" ; from query
/ "!" / "$" / "'" / "(" / ")"
/ "+" / "," / ";" / "=" ; from sub-delims
The resource-param "uri" refers to the URI-reference between the "<" The resource-param "uri" refers to the URI-reference between the "<"
and ">" characters of a link. Other resource-param values refer to and ">" characters of a link. Other resource-param values refer to
the link attribute they name. Filtering is performed by comparing the link attribute they name. Filtering is performed by comparing
the query-pattern against the value of the attribute identified by the query-pattern against the value of the attribute identified by
the resource-param for each link-value in the collection of resources the resource-param for each link-value in the collection of resources
identified by the URI path. identified by the URI path.
If the decoded query-pattern does not end with "*", a link value If the decoded query-pattern does not end with "*", a link value
matches the query only if the value of the attribute or URI-reference matches the query only if the value of the attribute or URI-reference
denoted by the resource-param is bytewise identical to the query- denoted by the resource-param is byte-wise identical to the query-
pattern. If the decoded query-pattern ends with "*", it is pattern. If the decoded query-pattern ends with "*", it is
sufficient that the remainder of the query-pattern be a prefix of the sufficient that the remainder of the query-pattern be a prefix of the
value denoted by the resource-param. A query-pattern of "*" will value denoted by the resource-param. A query-pattern of "*" matches
match that resource-param with an empty string value. It is not to an empty string value as well as to any other non-empty string.
expected that very constrained nodes support filtering. It is not expected that very constrained nodes support filtering.
Implementations not supporting filtering MUST simply ignore the query Implementations not supporting filtering MUST simply ignore the query
string and return the whole resource for unicast requests. string and return the whole resource for unicast requests.
When using a transfer protocol like the Constrained Application When using a transfer protocol like the Constrained Application
Protocol (CoAP) that supports multicast requests, special care is Protocol (CoAP) that supports multicast requests, special care needs
taken. A multicast request with a query string MUST NOT be responded to be taken. A multicast request with a query string SHOULD NOT be
to if filtering is not supported or if the filter does not match (to responded to if filtering is not supported or if the filter does not
avoid a needless response storm). match (to avoid a needless response storm). The exception is in
cases where the IP stack interface is not able to indicate that the
source address was multicast.
5. Examples 5. Examples
A few examples of typical link descriptions in this format follows. A few examples of typical link descriptions in this format follows.
Multiple resource descriptions in a representation are separated by Multiple resource descriptions in a representation are separated by
commas. Linefeeds never occur in the actual format, but are shown in commas. Linefeeds never occur in the actual format, but are shown in
these examples for readability. Although the following examples use these examples for readability. Although the following examples use
CoAP response codes, the examples are applicable to HTTP as well (the CoAP response codes, the examples are applicable to HTTP as well (the
corresponding response code would be 200 OK). corresponding response code would be 200 OK).
This example includes links to two different sensors sharing the same This example includes links to two different sensors sharing the same
interface description. Interface Description.
REQ: GET /.well-known/core REQ: GET /.well-known/core
RES: 2.05 "Content" RES: 2.05 "Content"
</sensors/temp>;rt="TemperatureC";if="sensor", </sensors/temp>;if="sensor",
</sensors/light>;rt="LightLux";if="sensor" </sensors/light>;if="sensor"
Without the linefeeds included for readability, the format actually Without the linefeeds included for readability, the format actually
looks as follows. looks as follows.
</sensors/temp>;rt="TemperatureC";if="sensor", </sensors/temp>;if="sensor",</sensors/light>;if="sensor"
</sensors/light>;rt="LightLux";if="sensor"
This example arranges link descriptions hierarchically, with the This example arranges link descriptions hierarchically, with the
entry point including a link to a sub-resource containing links about entry point including a link to a sub-resource containing links about
the sensors. the sensors.
REQ: GET /.well-known/core REQ: GET /.well-known/core
RES: 2.05 "Content" RES: 2.05 "Content"
</sensors>;rt="index" </sensors>;rt="index"
REQ: GET /sensors REQ: GET /sensors
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Thanks to Michael Stuber, Richard Kelsey, Cullen Jennings, Guido Thanks to Michael Stuber, Richard Kelsey, Cullen Jennings, Guido
Moritz, Peter Van Der Stok, Adriano Pezzuto, Lisa Dussealt, Alexey Moritz, Peter Van Der Stok, Adriano Pezzuto, Lisa Dussealt, Alexey
Melnikov, Gilbert Clark, Salvatore Loreto, Petri Mutka, Szymon Sasin, Melnikov, Gilbert Clark, Salvatore Loreto, Petri Mutka, Szymon Sasin,
Robert Quattlebaum, Robert Cragie, Angelo Castellani, Tom Herbst, Ed Robert Quattlebaum, Robert Cragie, Angelo Castellani, Tom Herbst, Ed
Beroset, Gilman Tolle, Robby Simpson, Colin O'Flynn and David Ryan Beroset, Gilman Tolle, Robby Simpson, Colin O'Flynn and David Ryan
for helpful comments and discussions that have shaped the document. for helpful comments and discussions that have shaped the document.
9. Changelog 9. Changelog
Changes from ietf-09 to ietf-10:
o Changed to SHOULD NOT for multiple relation types (#178).
o Changed to SHOULD NOT for multicast response repression (#179).
o Updated ABNF for queries (#179).
o Editorial improvements from WGLC comments.
Changes from ietf-08 to ietf-09: Changes from ietf-08 to ietf-09:
o Corrected ABNF and editorial nits. o Corrected ABNF and editorial nits.
o Elided empty responses to multicast request. o Elided empty responses to multicast request.
Changes from ietf-07 to ietf-08: Changes from ietf-07 to ietf-08:
o IESG submission nits. o IESG submission nits.
skipping to change at page 18, line 25 skipping to change at page 19, line 8
o Fixed the ABNF link-extension definitions (quotes around URIs, o Fixed the ABNF link-extension definitions (quotes around URIs,
integer definition). integer definition).
o Clarified that filtering is optional, and the query string is to o Clarified that filtering is optional, and the query string is to
be ignored if not supported (and the URL path processed as be ignored if not supported (and the URL path processed as
normally). normally).
o Required support of wildcard * processing if filtering is o Required support of wildcard * processing if filtering is
supported. supported.
o Removed the assumption of a default content-type assumption. o Removed the assumption of a default content-type.
10. References 10. References
10.1. Normative References 10.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO
10646", STD 63, RFC 3629, November 2003. 10646", STD 63, RFC 3629, November 2003.
 End of changes. 28 change blocks. 
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