QueryFS is a FUSE-based virtual filesystem that is based on queries. There are plugins to parse various query syntaxes and each query creates a virtual directory. Currently the most elaborate query language is SQL-based; you can either provide access to data stored in an SQL database, or keep an index of files in the SQL database and generate search directories with symlinks to found files. QueryFS and its SQL2 query DSL fully support creation of refinable searches: for example, the author has an index of downloaded email files; one can see all the distinct senders registered in the DB and then go into a directory of one sender and see all accounts that ever received an email from this sender.
Design Center is a Web application that allows users to change the colour of different layers in a photo. In a photo of a bedroom, there could be layers for the walls, the ceiling, and for the floor. The application lets users change the colour of each and see how a new paint job would look. If used on a furniture store's Web site, different layers could be used for beds, chairs, lampshades, etc. to allow customisation by users.