XEP-xxxx: REST with XMPP

Abstract
This specification defines how the Representational State Transfer (REST) architectural style can be applied to an XMPP overlay network. It specifies an XMPP protocol extension for accessing resources and transporting resource metadata and XML-REST encoded requests and responses between two XMPP entities.
Author
Alexander Stanik
Copyright
© 1999 – 2020 XMPP Standards Foundation. SEE LEGAL NOTICES.
Status

ProtoXEP

WARNING: This document has not yet been accepted for consideration or approved in any official manner by the XMPP Standards Foundation, and this document is not yet an XMPP Extension Protocol (XEP). If this document is accepted as a XEP by the XMPP Council, it will be published at <http://xmpp.org/extensions/> and announced on the <standards@xmpp.org> mailing list.
Type
Standards Track
Version
0.0.1 (2015-05-11)
Document Lifecycle
  1. Experimental
  2. Proposed
  3. Draft
  4. Final

1. Introduction

Representational State Transfer (REST) is an architectural style that is a coordinated set of constraints which also apply to the web. It aims at simplifying component implementations, reducing the complexity of distributed software elements, improving the performance, and increasing the scalability. In relation to the definition of a RESTful application programming interface (API) the uniform interface constraint is of high importance. It simplifies and decouples the architecture and makes REST components independent. The constraints for a uniform interface can be reduced to: the identification of resources, the self-descriptive representation of resources, and the self-descriptive manipulation of resources.

REST systems typically communicate over the Hypertext Transfer Protocol (HTTP) and are gaining large acceptance due to its growing support and its simplicity for implementation. RESTful web services are in this context a simpler alternative to SOAP [1] and WSDL-based Web services which are specified for the use with XMPP in SOAP over XMPP (XEP-0072) [2] and also a more powerful alternative to XML-RPC [3] which are specified as XMPP extension in Jabber-RPC (XEP-0009) [4].

The HTTP Over XMPP Transport (XEP-0332) [5] allows for designing REST services in the context of XMPP, but requires an implementation of both protocols: XMPP and HTTP. Furthermore, HTTP was selected in the past because of its degree of popularity, but has some drawbacks like the lack of discoverability of services. The REST with XMPP extension is a powerful protocol for cloud services that has several advantages in contrast to the traditional HTTP-based REST approach:

  1. services are discoverable and explorable,
  2. asynchronous invocation can be performed in parallel,
  3. generation of clients on the fly based on the capabilities of resources, and
  4. multiple input and output types definitions are possible.

The REST with XMPP protocol makes use of the <iq/> stanza in order to enable access, to create, to delete, or to modify resources within a XMPP network overlay. This specification defines two XML Schema files: one for exploring the capabilities of a resource and one for performing actions on a resource.

2. Requirements

The author has designed the REST with XMPP protocol with the following requirements in mind:

3. Resource Exploration

In order to explore the capabilities of a resource, the <iq/> stanza type "get" have to be used. The returned <iq/> stanza is either of type "error" or "result". If it is of type "result", the returned content has to be complied with the xwadl schema of this specification. The xwadl schema has been designed for providing a machine process-able description of a resource. It was inspired by the Web Application Description Language (WADL) standard delivered by the World Wide Web Consortium (W3C).

An <iq/> stanza of type "get" is returning an <iq/> stanza of type "result" that describes all actions that the requesting party can perform. The following example shows an exploration of a cloud provider's REST based interface for handling compute services.

Example 1. Exploration of an OpenStack interface for handling compute services
<iq type='get'
    from='requester@company-b.com/rest-client'
    to='company-a.com/openstack'
    id='rest1'>
  <resource_type xmlns="urn:xmpp:rest-xwadl" path="/compute" />
</iq>
      

In order to explore a resource, only the path to a resource is required. The counter party has to answer of such a request with a response that exposes all possible actions which can be performed on the resource located at the specified path. The following example illustrates a response that exposes all actions for this resource.

Example 2. Result of an exploration for handling compute services
<iq type="result"
    from="company-a.com/openstack"
    to="requester@company-b.com/rest-client"
    id="rest1">
  <resource_type xmlns="urn:xmpp:rest-xwadl" xmlns:xs="http://www.w3.org/2001/XMLSchema" path="/compute">
    <doc title="Compute resource management">
        Use one of the following actions to manage your compute instances!
    </doc>
    <method name="create">
      <request>
        <param name="image" required="true" repeating="false">
          <option link="remote"/>
        </param>
        <param name="flavors" repeating="false" default="m1.small">
          <option type="xs:string">m1.small</option>
          <option type="xs:string">m2.medium</option>
          <option type="xs:string">m3.large</option>
        </param>
        <param name="number" repeating="false" default="1">
          <doc title="number of requested virtual machnies"/>
          <option type="xs:integer"/>
        </param>
      </request>
      <response>
        <param name="newVM">
          <option link="list"/>
        </param>
      </response>
    </method>
    <method name="sla">
      <response>
        <param name="computeSla">
          <option mediaType="text/plain"/>
          <option mediaType="application/json"/>
        </param>
      </response>
    </method>
  </resource_type>
</iq>
      

This response exposes two methods that can be performed on the resource located at "/compute". The first method "create" can be used to create one or more virtual machines (VM). This method has three input parameters in its request and one output parameter in its response. If a client would like to perform this method, at least only a link to the location of an image is required. The other two parameters are optional. The server will respond to this method with a list of links to the instantiated VMs. A detailed example of how to access this method is illustrated in the Resource Access section.

The following subsections describe each component of a xwadl document in detail.

3.1 Resource Type

The "resource_type" element forms the root of a xwadl document and MAY comprises the following sub-elements: "doc", "grammars", and "method"

3.2 Documentation

Each xwadl-defined element down to the "param" can have one or more child "doc" elements that can be used to document that element. The doc element has "title" attributes which is a short plain text description of the element being documented. The "doc" element can have mixed content and may contain text and zero or more child elements.

3.3 Grammars

The "grammars" element acts as a container for definitions of the format of data exchanged during execution of the protocol described by the xwadl document and SHOULD be according to the XML Schema definition.

Example 3. Example xwadl document with a grammars element
<iq type="result"
    from="responder@company-a.com"
    to="requester@company-b.com/rest-client"
    id="rest1">
  <resource_type xmlns="urn:xmpp:rest-xwadl" xmlns:xs="http://www.w3.org/2001/XMLSchema" path="/address-book">
    <grammars>
      <doc title="Person List"/>
      <xs:element name="PersonList" type="MyStructType"/>
      <xs:complexType name="MyStructType">
        <xs:sequence>
          <xs:element name="Person" type="MyPersonType" maxOccurs="unbounded"/>
        </xs:sequence>
      </xs:complexType>
      <xs:complexType name="MyPersonType">
        <xs:sequence>
          <xs:element name="name" type="xs:string"/>
          <xs:element name="age" type="xs:integer"/>
        </xs:sequence>
      </xs:complexType>
    </grammars>
    <method name="POST">
      <request>
        <param name="persons" required="true" repeating="false">
          <option type="MyStructType"/>
        </param>
      </request>
      <response/>
    </method>
  </resource_type>
</iq>
      

3.4 Method

A method element describes the specific actions that can be performed on a resource targeted by the "path" attribute of the "resource_type" element. A method element is a child of a "resource_type" element and has a "name" attribute that identifies this method.

Additionally, each "method" MUST have one "request" and one "response" element which can be empty or be used to expose the optional parameters that this method can execute.

3.5 Request and Response

The "request" and the "response" element are according to the xwadl schema of type "call". They are identical by definition and describe the input and output data for accessing a resource.

Both elements describe the information to be included when applying a method to a resource. Both elements have no attributes and may contain one or more "param" elements as child elements.

3.6 Parameter

A "param" element describes a parameterized component of its parent element (either a request or a response). It can be identified by its "name" attribute and MUST have a minimum of one "option" element that defines one of a set of possible values for the parameter. In order to parameterize a component, the "param" element SHOULD specify a combination of the following attributes:

Some combinations of attributes do not make sense, e.g. the specification of "default=?" and "repeating=true", and SHOULD be considered application specific.

3.7 Option

An "option" element defines one of a set of possible types, representations, link type, or also values for the parameter. An "option" element MUST have one of the following attributes:

type

The "type" attribute indicates one possible type of the parameter as an XML qualified name, defaults to xs:string. It SHOULD specify the type of a single optional value. Multiple options with the same type but different values SHOULD specify a set of possible values which are acceptable as input for the parent parameter.

mediaType

The "mediaType" attribute indicates that the parent parameter acts as a media type selector for requests or responses. The value of the attribute is the media type that is expected. If a representation of an OPTIONAL media type is exposed, this representation can act as a template for manipulating a resource.

link

The "link" attribute is used to identify links to resources. It can have the value local, remote, or list. A local link links to another resource located at the same server entity. A remote link links to a resource located at another server entity anywhere in the XMPP network overlay. A link with a list value indicates a list of remote links that can be used for discovery or linking to a set of resources.

4. Resource Access

In order to access a resource, the <iq/> stanza type "set" has to be used. The returned <iq/> stanza is either of type "error" or "result". If it is of type "result", the returned content has to be complied with the xml-rest schema of this specification. The xml-rest schema has been designed for providing a xml-rest encoded payload for accessing a resource. An <iq/> stanza MUST NOT contain more than one method element with one request and one response. The following example illustrates how the create method of the previous example is requested. Here, the client requests three VMs which are based on an image that is available as resource on the client's side.

Example 4. Access of an OpenStack interface to create a virtual machnine
<iq type="set"
    from="requester@company-b.com/rest-client"
    to="company-a.com/openstack"
    id="rest2">
  <resource xmlns="urn:xmpp:xml-rest" xmlns:xs="http://www.w3.org/2001/XMLSchema" path="/compute">
    <method name="create">
      <request>
        <param name="image">
          <link>
            <to>requester@company-b.com/rest-client</to>
            <path>/images/myLinuxImage</path>
          </link>
        </param>
        <param name="number">
          <value type="xs:integer">3</value>
        </param>
      </request>
      <response>
        <param name="newVM">
          <resourceList/>
        </param>
      </response>
    </method>
  </resource>
</iq>
      

In order to make sure that both parties have a common understanding, the requester specifies also the expected responds type which has been exposed during the exploration step. The counter party has to answer such a request with the same request element and an extended complitation of the response element as illustrated in the example below.

Example 5. Result of an access to create a virtual machnine
<iq type="result"
    from="company-a.com/openstack"
    to="requester@company-b.com/rest-client"
    id="rest2">
  <resource xmlns="urn:xmpp:xml-rest" xmlns:xs="http://www.w3.org/2001/XMLSchema" path="/compute">
    <method name="create">
      <request>
        <param name="image">
          <link>
            <to>requester@company-b.com/rest-client</to>
            <path>/images/myLinuxImage</path>
          </link>
        </param>
        <param name="number">
          <value type="xs:integer">3</value>
        </param>
      </request>
      <response>
        <param name="newVM">
          <resourceList>
            <link>
              <to>dc1.company-a.com/openstack</to>
              <path>requester/vms/vm1</path>
            </link>
            <link>
              <to>dc2.company-a.com/openstack</to>
              <path>requester/vms/vm02</path>
            </link>
            <link>
              <to>dc3.company-a.com/openstack</to>
              <path>requester/vms/vm003</path>
            </link>
          </resourceList>
        </param>
      </response>
    </method>
  </resource>
</iq>
      

The following subsections describe each component of a xml-rest document in detail.

4.1 Resource

The "resource" element forms the root of an xml-rest document and MUST comprise only a single "method" sub-element. In contrast to the xwadl description, no further documentation or grammers are possible in order to keep the number of bytes as low as possible. In order to specify the resource to access, the "path" attribute is required.

4.2 Method

The "method" element MUST have one request element and one response element. Additionally, the "name" attribute is required in order to identify the action that has to be performed on the resource.

4.3 Request and Response

The "request" and the "response" element are according to the xml-rest schema of type "call". They are identical by definition and including the information for applying the method of a resource. Both elements have no attributes and may contain one or more "param" elements as child elements.

4.4 Parameter

Each "param" element has a "name" attribute to identify the parameter and a single sub-element that includes the data. Possible sub-elements are value, representation, link, or resourceList.

4.5 Value

The "value" element has a "type" attribute that specifies the type of the value.

4.6 Representation

The "representation" element has a "mediaType" attribute that specifies the media type of the representation.

A "link" element or a "resourceList" element have no attributes. While a link targets to a single local or remote location, a resource list is a set of links which are targeting to any resource in an XMPP overlay network. A link can be expressed in two forms: as XMPP resource link with a "to" (e.g. <to>requester@company-b.com/rest-client</to>) and a "path" (e.g. <path>/images/myLinuxImage</path>) element or as URI (<uri>xmpp://requester@company-b.com/rest-client?/images/myLinuxImage</uri>).

5. Use Cases

5.1 Multi-Dimensional Resource Placement

The REST with XMPP protocol enables a multi-dimensional resource placement. The following examples show how different resources can be placed within a single server entity:

Example 6. A request to a server
<iq type='set'
    from='requester@company-b.com/rest-client'
    to='company-a.com'
    id='rest1'>
  <resource xmlns="urn:xmpp:xml-rest" path="/">
    ...
  </resource>
</iq>
  
Example 7. A request to a server with a JID contained a resource part
<iq type='set'
    from='requester@company-b.com/rest-client'
    to='company-a.com/resource'
    id='rest1'>
  <resource xmlns="urn:xmpp:xml-rest" path="/">
    ...
  </resource>
</iq>
  
Example 8. A request to a server with a JID contained a local part
<iq type='set'
    from='requester@company-b.com/rest-client'
    to='responder@company-a.com'
    id='rest1'>
  <resource xmlns="urn:xmpp:xml-rest" path="/">
    ...
  </resource>
</iq>
  
Example 9. A request to a server with a JID contained a local and a resource part
<iq type='set'
    from='requester@company-b.com/rest-client'
    to='responder@company-a.com/resource'
    id='rest1'>
  <resource xmlns="urn:xmpp:xml-rest" path="/">
    ...
  </resource>
</iq>
  
Example 10. A request to a server with a JID contained a local and a resource part, but accesses another resource
<iq type='set'
    from='requester@company-b.com/rest-client'
    to='responder@company-a.com/resource'
    id='rest1'>
  <resource xmlns="urn:xmpp:xml-rest" path="/resource/">
    ...
  </resource>
</iq>
  

All examples above are accessing different resources. A variation of the path attribute of the resource element would also combine the presented JIDs and referring to different resources. Further examples are possible to show how different resources can be located at a single server entity.

6. Service Discovery

If an entity supports the REST with XMPP protocol, it SHOULD advertise that fact in response to Service Discovery (XEP-0030) [6] information ("diso#info") requests by returning an identity of "automation/rest" and a feature of "jabber:iq:rest":

Example 11. A disco#info query
<iq type='get'
    from='requester@company-b.com/rest-client'
    to='responder@company-a.com/rest-server'
    id='disco1'>
  <query xmlns='http://jabber.org/protocol/disco#info'/>
</iq>
  
Example 12. A disco#info response
<iq type='result'
    to='requester@company-b.com/rest-client'
    from='responder@company-a.com/rest-server'
    id='disco1'>
  <query xmlns='http://jabber.org/protocol/disco#info'>
    <identity category='automation' type='rest'/>
    <feature var='jabber:iq:rest'/>
  </query>
</iq>
  

7. Security Considerations

Determining when and how a resource can be accessed or modified based on permissions or rights are considered outside the scope of this document. Although such mechanisms SHOULD be considered specifically to the application and/or implementation of this document, future specifications may address these concerns.

8. IANA Considerations

REQUIRED.

9. XMPP Registrar Considerations

9.1 Protocol Namespaces

The XMPP Registrar [7] includes 'urn:xmpp:rest:xwadl' and 'urn:xmpp:rest:xml' in its registry of protocol namespaces.

9.2 Service Discovery Identity

The XMPP Registrar includes a Service Discovery type of "rest" within the "automation" category in its registry of service discovery identities.

10. XML Schema

10.1 XWADL Schema

<?xml version='1.0' encoding='UTF-8'?>

<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
	targetNamespace="urn:xmpp:rest-xwadl" xmlns="urn:xmpp:rest-xwadl"
	elementFormDefault="qualified">

	<xs:annotation>
		<xs:documentation>
			The protocol documented by this schema is defined in
			XEP-xxxx: http://www.xmpp.org/extensions/xep-xxxx.html
		</xs:documentation>
	</xs:annotation>

	<xs:element name="resource_type">
		<xs:complexType>
			<xs:sequence>
				<xs:element ref="doc" minOccurs="0" maxOccurs="unbounded" />
				<xs:element ref="grammars" minOccurs="0" />
				<xs:element ref="method" minOccurs="0" maxOccurs="unbounded" />
			</xs:sequence>
			<xs:attribute name="path" type="xs:string" use="required" />
		</xs:complexType>
	</xs:element>

	<xs:element name="doc">
		<xs:complexType mixed="true">
			<xs:sequence>
				<xs:any namespace="##other" processContents="lax" minOccurs="0"
					maxOccurs="unbounded" />
			</xs:sequence>
			<xs:attribute name="title" type="xs:string" />
		</xs:complexType>
	</xs:element>

	<xs:element name="grammars">
		<xs:complexType>
			<xs:sequence>
				<xs:element ref="doc" minOccurs="0" maxOccurs="unbounded" />
				<xs:any namespace="##other" processContents="lax" minOccurs="0"
					maxOccurs="unbounded" />
			</xs:sequence>
		</xs:complexType>
	</xs:element>

	<xs:element name="method">
		<xs:complexType>
			<xs:sequence>
				<xs:element ref="doc" minOccurs="0" maxOccurs="unbounded" />
				<xs:element ref="request" minOccurs="0" maxOccurs="1" />
				<xs:element ref="response" minOccurs="0" maxOccurs="1" />
			</xs:sequence>
			<xs:attribute name="name" type="xs:string" />
		</xs:complexType>
	</xs:element>

	<xs:element name="request" type="call" />

	<xs:element name="response" type="call" />

	<xs:complexType name="call">
		<xs:sequence>
			<xs:element ref="doc" minOccurs="0" maxOccurs="unbounded" />
			<xs:element ref="param" minOccurs="0" maxOccurs="unbounded" />
		</xs:sequence>
	</xs:complexType>

	<xs:element name="param">
		<xs:complexType>
			<xs:sequence>
				<xs:element ref="doc" minOccurs="0" maxOccurs="unbounded" />
				<xs:element ref="option" minOccurs="1" maxOccurs="unbounded" />
			</xs:sequence>
			<xs:attribute name="name" type="xs:string" use="required" />
			<xs:attribute name="default" type="xs:string" />
			<xs:attribute name="required" type="xs:boolean" default="false" />
			<xs:attribute name="repeating" type="xs:boolean" default="false" />
		</xs:complexType>
	</xs:element>

	<xs:element name="option">
		<xs:complexType mixed="true">
			<xs:sequence>
				<xs:any namespace="##other" processContents="lax" minOccurs="0"
					maxOccurs="unbounded" />
			</xs:sequence>
			<xs:attribute name="type" type="xs:QName" default="xs:string" />
			<xs:attribute name="mediaType" type="xs:string" />
			<xs:attribute name="link" type="linkTarget" />
		</xs:complexType>
	</xs:element>

	<xs:simpleType name="linkTarget">
		<xs:restriction base="xs:string">
			<xs:enumeration value="local" />
			<xs:enumeration value="remote" />
			<xs:enumeration value="list" />
		</xs:restriction>
	</xs:simpleType>

</xs:schema>
	

10.2 XML-REST Schema

<?xml version='1.0' encoding='UTF-8'?>

<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
	targetNamespace="urn:xmpp:xml-rest" xmlns="urn:xmpp:xml-rest"
	elementFormDefault="qualified">

	<xs:annotation>
		<xs:documentation>
			The protocol documented by this schema is defined in
			XEP-xxxx: http://www.xmpp.org/extensions/xep-xxxx.html
		</xs:documentation>
	</xs:annotation>

	<xs:element name="resource">
		<xs:complexType>
			<xs:sequence>
				<xs:element ref="method" minOccurs="1" maxOccurs="1" />
			</xs:sequence>
			<xs:attribute name="path" type="xs:string" use="required" />
		</xs:complexType>
	</xs:element>

	<xs:element name="method">
		<xs:complexType>
			<xs:sequence>
				<xs:element ref="request" minOccurs="0" maxOccurs="1" />
				<xs:element ref="response" minOccurs="0" maxOccurs="1" />
			</xs:sequence>
			<xs:attribute name="name" type="xs:string" />
		</xs:complexType>
	</xs:element>

	<xs:element name="request" type="call" />

	<xs:element name="response" type="call" />

	<xs:complexType name="call">
		<xs:sequence>
			<xs:element ref="param" minOccurs="0" maxOccurs="unbounded" />
		</xs:sequence>
	</xs:complexType>

	<xs:element name="param">
		<xs:complexType>
			<xs:choice minOccurs="0" maxOccurs="1">
				<xs:element ref="value" />
				<xs:element ref="representation" />
				<xs:element ref="resourceList" />
				<xs:element ref="link" />
			</xs:choice>
			<xs:attribute name="name" type="xs:string" use="required" />
		</xs:complexType>
	</xs:element>

	<xs:element name="value">
		<xs:complexType mixed="true">
			<xs:sequence>
				<xs:any namespace="##other" processContents="lax" minOccurs="0"
					maxOccurs="unbounded" />
			</xs:sequence>
			<xs:attribute name="type" type="xs:QName" use="required" />
		</xs:complexType>
	</xs:element>

	<xs:element name="representation">
		<xs:complexType mixed="true">
			<xs:sequence>
				<xs:any namespace="##other" processContents="lax" minOccurs="0"
					maxOccurs="unbounded" />
			</xs:sequence>
			<xs:attribute name="mediaType" type="xs:string" use="required" />
		</xs:complexType>
	</xs:element>

	<xs:element name="resourceList">
		<xs:complexType>
			<xs:sequence>
				<xs:element ref="link" minOccurs="0" maxOccurs="unbounded" />
			</xs:sequence>
		</xs:complexType>
	</xs:element>

	<xs:element name="link">
		<xs:complexType>
			<xs:choice minOccurs="1" maxOccurs="1">
				<xs:sequence>
					<xs:element name="to" type="xs:string" minOccurs="0"
						maxOccurs="1" />
					<xs:element name="path" type="xs:string" minOccurs="1"
						maxOccurs="1" />
				</xs:sequence>
				<xs:element name="uri" type="xs:string" />
			</xs:choice>
		</xs:complexType>
	</xs:element>

</xs:schema>
	

Appendices

Appendix A: Document Information

Series
XEP
Number
xxxx
Publisher
XMPP Standards Foundation
Status
ProtoXEP
Type
Standards Track
Version
0.0.1
Last Updated
2015-05-11
Approving Body
XMPP Council
Dependencies
XMPP Core
Supersedes
None
Superseded By
None
Short Name
NOT_YET_ASSIGNED

This document in other formats: XML  PDF

Appendix B: Author Information

Alexander Stanik
Email
alexander.stanik@tu-berlin.de
URI
http://www.cit.tu-berlin.de/

Copyright

This XMPP Extension Protocol is copyright (c) 1999 - 2014 by the XMPP Standards Foundation (XSF).

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Permission is hereby granted, free of charge, to any person obtaining a copy of this specification (the "Specification"), to make use of the Specification without restriction, including without limitation the rights to implement the Specification in a software program, deploy the Specification in a network service, and copy, modify, merge, publish, translate, distribute, sublicense, or sell copies of the Specification, and to permit persons to whom the Specification is furnished to do so, subject to the condition that the foregoing copyright notice and this permission notice shall be included in all copies or substantial portions of the Specification. Unless separate permission is granted, modified works that are redistributed shall not contain misleading information regarding the authors, title, number, or publisher of the Specification, and shall not claim endorsement of the modified works by the authors, any organization or project to which the authors belong, or the XMPP Standards Foundation.

Disclaimer of Warranty

## NOTE WELL: This Specification is provided on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, express or implied, including, without limitation, any warranties or conditions of TITLE, NON-INFRINGEMENT, MERCHANTABILITY, or FITNESS FOR A PARTICULAR PURPOSE. In no event shall the XMPP Standards Foundation or the authors of this Specification be liable for any claim, damages, or other liability, whether in an action of contract, tort, or otherwise, arising from, out of, or in connection with the Specification or the implementation, deployment, or other use of the Specification. ##

Limitation of Liability

In no event and under no legal theory, whether in tort (including negligence), contract, or otherwise, unless required by applicable law (such as deliberate and grossly negligent acts) or agreed to in writing, shall the XMPP Standards Foundation or any author of this Specification be liable for damages, including any direct, indirect, special, incidental, or consequential damages of any character arising out of the use or inability to use the Specification (including but not limited to damages for loss of goodwill, work stoppage, computer failure or malfunction, or any and all other commercial damages or losses), even if the XMPP Standards Foundation or such author has been advised of the possibility of such damages.

IPR Conformance

This XMPP Extension Protocol has been contributed in full conformance with the XSF's Intellectual Property Rights Policy (a copy of which may be found at <http://xmpp.org/extensions/ipr-policy.shtml> or obtained by writing to XSF, P.O. Box 1641, Denver, CO 80201 USA).

Visual Presentation

The HTML representation (you are looking at) is maintained by the XSF. It is based on the YAML CSS Framework, which is licensed under the terms of the CC-BY-SA 2.0 license.

Appendix D: Relation to XMPP

The Extensible Messaging and Presence Protocol (XMPP) is defined in the XMPP Core (RFC 6120) and XMPP IM (RFC 6121) specifications contributed by the XMPP Standards Foundation to the Internet Standards Process, which is managed by the Internet Engineering Task Force in accordance with RFC 2026. Any protocol defined in this document has been developed outside the Internet Standards Process and is to be understood as an extension to XMPP rather than as an evolution, development, or modification of XMPP itself.

Appendix E: Discussion Venue

The primary venue for discussion of XMPP Extension Protocols is the <standards@xmpp.org> discussion list.

Discussion on other xmpp.org discussion lists might also be appropriate; see <http://xmpp.org/about/discuss.shtml> for a complete list.

Errata can be sent to <editor@xmpp.org>.

Appendix F: Requirements Conformance

The following requirements keywords as used in this document are to be interpreted as described in RFC 2119: "MUST", "SHALL", "REQUIRED"; "MUST NOT", "SHALL NOT"; "SHOULD", "RECOMMENDED"; "SHOULD NOT", "NOT RECOMMENDED"; "MAY", "OPTIONAL".

Appendix G: Notes

1. SOAP <http://www.w3.org/TR/SOAP/>.

2. XEP-0072: SOAP over XMPP <https://xmpp.org/extensions/xep-0072.html>.

3. XML-RPC <http://www.xmlrpc.com/spec>.

4. XEP-0009: Jabber-RPC <https://xmpp.org/extensions/xep-0009.html>.

5. XEP-0332: HTTP Over XMPP Transport <https://xmpp.org/extensions/xep-0332.html>.

6. XEP-0030: Service Discovery <https://xmpp.org/extensions/xep-0030.html>.

7. The XMPP Registrar maintains a list of reserved protocol namespaces as well as registries of parameters used in the context of XMPP extension protocols approved by the XMPP Standards Foundation. For further information, see <https://xmpp.org/registrar/>.

Appendix H: Revision History

Note: Older versions of this specification might be available at http://xmpp.org/extensions/attic/

  1. Version 0.0.1 (2015-05-11)

    First draft.

    as

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