Referring the concept of the symmetric difference of sets,from the viewpoint of the granular computing,knowledge distance in information systems is defined in the paper,and its properties are studied too.

This paper introduces the notion of "distance of knowledge",and it substitutes for these factors such as knowledge coding,abstraction extent and the buy s knowledge base.

During bargaining over the price of knowledge,the buyer and the seller evaluate synthetically the trust relation between them and the distance of knowledge away from the buyer to overcome the obstacles of information asymmetry,and adjust the price according to it until they are consistent with the price.

The distance sense in artistic creation and artiseic appreciation;

Distance estimation is the behavior in actual spatial environment, which is based on acquiring the distance knowledge.

Based on the theory of passive RFID technology and antenna scattering,some computation methods for radar cross-section of tag antennas with different loads are derived,and by integrating the radar cross-section with electromagnetic propagation environment,the identification range of passive radio frequency identification is theoretically analyzed.