Techniques are presented for selecting one or more items from a collection of items. To select the one or more items, an interface is provided that is adapted to allow a user to define one or more weights. Each weight corresponds to one of a number of similarity criteria. Each item also corresponds to the number of similarity criteria. The one or more weights define a similarity function. The similarity function is applied to the one or more similarity criteria corresponding to the one or more weights and to each of the items in order to select one or more items from the collection of items. The interface can comprise movable markers corresponding to similarity criteria. Locations of the movable markers can be used to weight similarity criteria when creating the similarity function.