1. A system for linking together digital information objects of a digital information space comprising: at least one overlay maintained outside of the digital information space, at least a portion of the at least one overlay passed to an agent for information processing; at least one concept node within each overlay, each concept node expressing one concept, each concept defined by at least one keyword; and at least one information node within each overlay, each information node representing one of the digital information objects; wherein a link between an accessed digital information object in the digital information space and each of the at least one concept node is established by the user if the accessed digital information object and the overlay include at least one common concept, the link being omitted absent at least one common concept.