1. A method performed by a data processing apparatus, the method comprising: receiving a search query, the search query comprising a query term and a query label term, the query label term being a categorical identifier; identifying one or more resources in a search result set responsive to the search query, wherein each of the one or more resources has an associated matching label term that matches the query label term and an associated non-matching label term that does not match the query label term, each associated label term being the categorical identifier describing each resource and having been associated with the resource by a respective entity; determining, for each of the one or more resources: a trust rank of the entity that associated the associated matching label term with the resource, wherein the trust rank indicates whether a user trusts the associated matching label term of the resource, and increasing a relevance score of each resource that has the associated matching label term based on the respective trust rank, the relevance score indicating a degree of relevance between the respective resource and the query term; ranking each of the one or more resources in the search result set based on the respective relevance scores; annotating, with a name of the respective entity that associated the matching label term with each resource, indicia identifying each resource of the ranked search result set; and providing the indicia in a response to the search query.