The Internet provides access to a wide variety of resources, for example, video files, image files, audio files, or Web pages, including content for particular subjects, book articles, or news articles. A search system can select one or more resources in response to receiving a search query. A search query is data that a user submits to a search engine to satisfy the user's informational needs. The search queries are usually in the form of text, e.g., one or more query terms. The search system selects and scores resources based on their relevance to the search query and on their importance relative to other resources to provide search results that link to the selected resources. The search results are typically ordered according to the scores and presented according to this order.
A search query, however, is often an incomplete expression of a user's informational need. Thus, a user may often refine a search query after reviewing search results, or may select a “suggested query” that is provided by a search engine to conduct another search. A user may also attempt to filter within a set of search results. However, the user may need to generate a filter term or operation, or rely on “hardcoded” filters that require expert knowledge and programming ahead of time, together with manual internationalization, in order to be effective. Furthermore, given the dynamic nature of the corpus of resources available over the Internet, new filtering terms may be emergent and escape the notice of both the user and resource curators.