Developing Feeds with RSS and Atom

Name

mod_threading

Synopsis

mod_threading provides a system to describe the children of an item (for example, replies to a weblog entry). This module is still in a state of flux; a great deal of work is being done by many people on the idea of descriptions of message threads within RSS and RDF. This is one of the goals of the ThreadML development effort (http://www.threadsml.org/).

With this in mind, mod_threading can get complicated quickly. Unfortunately, as complex as you might logically make it, the lack of standardization means that anything but the simplest usage will likely be misunderstood by most parsers. Therefore, in this chapter we restrict ourselves to defining children only within the limited scope of a single document. If true message threading is your goal, check with the mailing lists and weblogs linked to by the ThreadsML effort for more details.

Namespace

mod_threading takes the prefix thr: and the identifying URI http://purl.org/rss/1.0/modules/threading/. Hence, the root element:

<rdf:RDF xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
         xmlns="http://purl.org/rss/1.0/"
         xmlns:thr="http://purl.org/rss/1.0/modules/threading/"
>

Element

There’s only one element within mod_threading; it’s a subelement of item*, and it contains an rdf:Seq containing rdf:li elements of URIs representing items that are children of the item:

<thr:children>
  <rdf:Seq>
    <rdf:li rdf:resource="URI OF CHILD ITEM" />
  </rdf:Seq>
</thr:children>

For simplicity’s sake, the child item, and hence ...