8. A system comprising one or more computers configured to perform operations comprising: obtaining, by a search engine system, respective registration information from each of a plurality of publishers, the registration information including a location of respective enrichment information to be added to search results identifying resources provided by the respective publisher, each of the publishers being publishers registered with the search engine system; storing the registration information from the plurality of publishers for later use by the search engine system; receiving, by the search engine system, a query from a user; identifying, by the search engine system, a plurality of responsive resources, the plurality of responsive resources including a first responsive resource; determining, by the search engine system, that the first responsive resource is a resource for a first publisher that is associated with enrichment information; obtaining first enrichment information from the location of respective enrichment information included in the registration information provided by the first publisher to the search engine system; and providing, by the search engine system, in a response to the query, an enriched search result that identifies the first responsive resource and includes the first enrichment information.
8. A system comprising one or more computers configured to perform operations comprising: obtaining, by a search engine system, respective registration information from each of a plurality of publishers, the registration information including a location of respective enrichment information to be added to search results identifying resources provided by the respective publisher, each of the publishers being publishers registered with the search engine system; storing the registration information from the plurality of publishers for later use by the search engine system; receiving, by the search engine system, a query from a user; identifying, by the search engine system, a plurality of responsive resources, the plurality of responsive resources including a first responsive resource; determining, by the search engine system, that the first responsive resource is a resource for a first publisher that is associated with enrichment information; obtaining first enrichment information from the location of respective enrichment information included in the registration information provided by the first publisher to the search engine system; and providing, by the search engine system, in a response to the query, an enriched search result that identifies the first responsive resource and includes the first enrichment information. 9. The system of claim 8 , wherein determining that the first responsive resource is associated with enrichment information comprises: identifying responsive enrichment information, responsive enrichment information being enrichment information that is responsive to the query; and determining that the first responsive resource is associated with the responsive enrichment information.