Please note, this is a STATIC archive of website developer.mozilla.org from 03 Nov 2016, cach3.com does not collect or store any user information, there is no "phishing" involved.
A triple can be included inside a rule's conditions element. It is used to check for an assertion within a graph. If such an assertion exists, the rule may match, assuming that all the conditions match. If the assertion does not exist, the rule will not match. Both the subject and object attributes may be variables.
The subject of a triple is an RDF resource. In an RDF file this would usually be an RDF Description element. The predicate would be a child element or property. For example, for a bookmark resource, the name and URL would be predicates. They should be specified in their full URI form. The object is the value of the RDF property.
More information is available in the XUL tutorial.