中文摘要：

计算两个时态粒点在任意时态粒度下的差值是时态断言的基础，提出基于时态粒度的层次映射转换方法，将时态粒点映射为各时态粒度下的可列集，差运算可转换为不同粒度映射下的自然数差运算．并论证了时态论域T与自然数集N间的对等关系以及映射的连续性，证明了方法的正确性．克服了弹性时态粒度的影响，适应任何基于非规则时态粒度集或者自定义时态粒度集上的时态粒点差运算．

英文摘要：

Temporal modeling and calculus are the fundamental logic problems in temporal information system. The subtraction operation between two temporal points with any granularity is the basis of the temporal assertion, which is hard to deal with. From the point view of granular computing, the semantics and properties of temporal granularities are discussed according to the temporal partition. Temporal primitives are characterized based on the temporal granularities. Furthermore, the method of the granularity subtraction operation is proposed based on the mapping and conversion of different granularity hierarchies. The temporal points could be mapped to the countable set with any temporal granularity, and the subtraction operation between two temporal points could be converted to the subtraction operation between two natural numbers. The equality between temporal domain T and natural set N and continuity of the mapping are discussed and proved, which supports that the proposed method is correct, and the effect of the flexible temporal granularity is overcome. Finally, an algorithm for temporal granularity converting functions is proposed in the context of the calendar system. The proposed method could be adapted to the subtraction operation between two temporal points from any irregular temporal points set or user-defined temporal points set.