1. A data storage and/or retrieval system implemented on one or more digital data processing systems, comprising: storage media comprising a plurality of data tunnels for each entity type and a fixed plurality of data tunnels for each attribute, one or more of which data tunnels comprise a plurality of data cells, wherein each of the data cells contain data associated with a respective instance of an attribute for a respective instance of an entity type, wherein for one or more of the data tunnels, the data cells in each of which have data for which a respective operator evaluates to a boolean result indicating either the likely possibility or the impossibility of a respective instance of an attribute being characterised by said operator for a given set of one or more operands, and a storage engine that is in communications coupling with the storage media and that accesses one or more data tunnels based on one or more of said operators and a given set of one or more operands.