The more a communication system grows and increases its diversity, the more likely it is that conflicts arise over which content is acceptable and which is not. In addition, some content may be psychologically triggering or harmful to different people or age groups, while the same content may be desirable to share and talk about in other groups.
This specification intends to provide a machine-readable and extensible way of conveying the kinds and classes of content which are acceptable, and hence to be expected, on a service. Such a service can be an instant messaging account server, a Multi-User Chat (XEP-0045)  service or room, a Mediated Information eXchange (MIX) (XEP-0369)  service or channel or any other entity which is able to publish extensions as per Service Discovery Extensions (XEP-0128) .
The content ratings are provided as a set of free-form strings, scoped by a type URI.
This idea is not new. The W3C for instance has had two initiatives revolving around labelling content for the web. The Platform for Internet Content Selection (PICS) has been superseded by the Protocol for Web Description Resources (POWDER).
While the PICS approach is roughly similar to what this document intends to achieve, the POWDER standard goes way beyond that and provides much more extension points, at the cost of higher complexity.
Security Labels in XMPP (XEP-0258)  provides a way to embed security labels in contexts where clearance to view specific content is required. While the rating of content is roughly similar, the XEP-0258 standard goes beyond that by placing restrictions on entities which carry such labels in a way which is not desirable for this standard.
Specifically, the document states that supporting implementations MUST NOT
<securitylabel/> element outside of contexts of specifications
known to them, which could pose interoperability issues if that element was
reused for this specification.
A free-form string qualified by a
Content Rating: A set of Content Labels which describe the describes the classes of content which may be encountered at the entity to which the rating applies.
The Content Rating is conveyed using a set of free-form strings qualified
type attribute, the Content Labels.
A Content Label is represented by a single XML
qualified by the
type attribute MUST be a URI. It defines the format of the CDATA
contained in the
<simple-label/> element. The character data of the
<simple-label/> element MUST NOT contain control codes (including newline
and horizontal tab).
type URI must be URL-encoded, escaping all whitespace.
A Content Rating is represented by a
<content-rating/> XML element qualified
urn:xmpp:crl:0 namespace. It carries zero or more
child elements as described above.
Future extensions MAY specify other child elements for
separate namespaces. See the business rules for an approach for handling those
If the format needs to be conveyed in plain text form, for example to carry the list of labels in Service Discovery Extensions (XEP-0128)  or a Data Forms (XEP-0004)  configuration form, the following algorithm is to be applied:
An entity may publish a content self-rating using Service Discovery Extensions (XEP-0128) . For this, a
Data Forms (XEP-0004)  form with the
FORM_TYPE is defined.
All labels are mapped to a single
Each line in the
text-multi field is prefixed with the
key of the
<simple-label/> element. The
key is followed by a single
space character (U+0020), followed by the character data of the
Entities with sufficient permissions to modify Multi-User Chat (XEP-0045)  room configuration SHOULD be offered a text-multi form field of the format described above. If offered this field MUST be mapped to the format described above in the Service Discovery (XEP-0030)  response of the room.
<content-rating/>. Depending on the level of certainty required in interpreting a
<content-rating/>element, implementations for example choose to either silently ignore unknown elements or treat them as the worst possible rating.
Implementations which convert the labels to human-readable strings need to translate those strings. For now, no provision is made to provide pre-translated texts.
REQUIRED for protocol specifications.
This document in other formats: XML PDF
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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.
The primary venue for discussion of XMPP Extension Protocols is the <email@example.com> discussion list.
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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".
Note: Older versions of this specification might be available at http://xmpp.org/extensions/attic/