Data indicative of membership of at least one of a plurality of content classes is made available for each one of a collection of content items. A method of selecting at least one item includes displaying a representation of sections of a geo-metrical construct occupying an at least one-dimensional space. The geometrical construct is partitioned into sections in accordance with a mapping between the at least one-dimensional space and a domain of the data indicative of class membership, such that each section represents a class. A signal defining a sub-space within the space is received, and the mapping is used to effect a selection of at least one item of content data commensurate with the defined sub-space.