Syndication Feed SOQL and Mapping Syntax
Syndication feed services use a SOQL query and mapping specification that
allows applications to point to sets of objects and individual objects and to traverse
relationships between objects. Several options can be added as query string parameters to filter
and control how the data is presented. Syndication feeds can be defined for public
sites.
For full information about the limitations on SOQL in query feed definitions, see the Salesforce online help for syndication feeds.