9. A non-transitory computer-readable storage medium storing instruction that, when executed by one or more computers, cause the one or more computers to perform a method comprising: maintaining an index for a collection of resources, wherein each resource in the collection is associated with zero or more respective entity tags, and wherein each entity tag includes a respective entity name; receiving a search query from a user device; identifying a plurality of resources in the collection that satisfy the search query using the index; determining that (i) the search query includes more than a first threshold number of distinct nouns that are hypernyms, (ii) the search query includes more than a different, second threshold number of distinct adjectives, or (iii) the plurality of resources is associated with more than a different, third threshold number of distinct entity tags; in response to determining that (i) the search query includes more than a first threshold number of distinct nouns that are hypernyms, (ii) the search query includes more than a different, second threshold number of distinct adjectives, or (iii) the plurality of resources is associated with more than a different, third threshold number of distinct entity tags, processing each entity tag that is associated with a respective identified resource as a current entity tag, including: determining whether or not a user interface (UI) element that is representative of the current entity tag is to be displayed on the user device; and in response to determining that the UI element that is representative of the current entity tag is to be displayed on the user device, generating UI element data that, when processed by the user device, causes the user device to display a UI element that is labeled with the entity name in the current entity tag and is selectable by a user operating the user device to initiate a search for resources that are associated with an entity that is identified by the entity name in the current entity tag; generating a results page that includes the UI element data; and sending the results page to the user device.
12. The non-transitory computer-readable storage medium of claim 9 , wherein each resource in the collection is associated with zero or more respective keyword tags, wherein each keyword tag includes a respective keyword, and wherein the method further comprises: processing each keyword tag that is associated with a respective identified resource as a current keyword tag, including: determining whether or not the keyword included in the current keyword tag is an entity name, and if so, generating an entity tag that includes the keyword; and associating the entity tag with the identified resource that is associated with the current keyword tag.