9. An information retrieval and communication system comprising: a namespace data store configured to store a plurality of grouping labels, wherein each grouping label is includable by a plurality of publishers in a plurality of content items in a corpus; an index data store configured to store an index identifying, for each of the plurality of grouping labels stored in the namespace data store, each content item, of the plurality of content items, in the corpus that includes said each grouping label of the plurality of grouping labels; and an information server including: a client interface module configured to receive requests from a client computer system for identification of content items related to a first content item, wherein each request including a first grouping label extracted from the first content item; and an index interface module configured to access the index to identify a second content item having the first grouping label extracted from the first content item included therein, wherein the client interface module is further configured to return a reference to the second content item to the client computer system.
9. An information retrieval and communication system comprising: a namespace data store configured to store a plurality of grouping labels, wherein each grouping label is includable by a plurality of publishers in a plurality of content items in a corpus; an index data store configured to store an index identifying, for each of the plurality of grouping labels stored in the namespace data store, each content item, of the plurality of content items, in the corpus that includes said each grouping label of the plurality of grouping labels; and an information server including: a client interface module configured to receive requests from a client computer system for identification of content items related to a first content item, wherein each request including a first grouping label extracted from the first content item; and an index interface module configured to access the index to identify a second content item having the first grouping label extracted from the first content item included therein, wherein the client interface module is further configured to return a reference to the second content item to the client computer system. 15. The system of claim 9 further comprising: an index builder configured to create the index and store the index in the index data store.