Editor's Note: This is version 1.1 of this document, published Oct. 19, 2006.

The Trackback namespace enables an RSS 1.0 or RSS 2.0 syndication feed to support trackback, a protocol for peer-to-peer communication between web sites that publish related content.

In its simplest form, trackback is a means of sending a message that lets a site know you've published a link to one of its pages.

The message, which is called a trackback ping, conveys three pieces of information from the sender to another site:

1. I have published a web page about something on your site.
2. Here's a text excerpt of what I have written.
3. Here's a link to the page.

In order to work, both the sender and the receiver must support the trackback protocol. Trackback pings are collected automatically and often presented in a manner similar to visitor comments.

The ping must be sent to a trackback URL, a script that understands trackback and can do something useful with the information. The trackback URL identifies the page that's being linked on the sender's site.

In this documentation, the key words MAY, MUST, MUST NOT, OPTIONAL, RECOMMENDED, REQUIRED, SHALL, SHALL NOT, SHOULD, and SHOULD NOT are to be interpreted as described in RFC 2119.

The Trackback namespace requires the http://madskills.com/public/xml/rss/module/trackback/ declaration in the RSS element.

<rss xmlns:trackback="http://madskills.com/public/xml/rss/module/trackback/">

Sample feeds demonstrate how to incorporate elements from this namespace in an RSS 1.0 or RSS 2.0 feed.

The about element, when present in an item, identifies a trackback URL on another site that was pinged in response to the item (OPTIONAL).

An RSS 1.0 feed MUST define the URL as the value of the element's resource attribute in the RDF namespace.

<trackback:about rdf:resource="http://ekzemplo.com/tb.cgi?tb\_id=180"/>

An RSS 2.0 feed MUST define the URL as the element's value.

<trackback:about>http://ekzemplo.com/tb.cgi?tb_id=180</trackback:about>

An item MAY contain more than one <trackback:about> element.

The <trackback:ping> element, when present in an item, identifies the item's trackback URL (OPTIONAL).

An RSS 1.0 feed MUST define the URL as the value of the element's resource attribute in the RDF namespace.

<trackback:ping rdf:resource="http://dallas.example.com/trackback.php?id=3135"/>

An RSS 2.0 feed MUST define the URL as the element's value.

<trackback:ping>http://dallas.example.com/trackback.php?id=3135</trackback:ping>

An item MUST NOT contain more than one <trackback:ping> element.

Copyright © 2006 RSS Advisory Board. Redistribution and reuse of this document is permitted under the terms of the Creative Commons Attribution-ShareAlike 2.0 license.

The Trackback Namespace for RSS was created by Justin Klubnik, Benjamin Trott and Mena Trott. Comments and corrections regarding this document are encouraged on the RSS-Public mailing list.