Bitemporal relational algebra with temporal variables based on BCDM
基于BCDM的含有变量的双时态关系代数研究*

In BCDM (bitemporal conceptual data model), the valid time variable Now and the transaction time variable UC resolved the problem about the frequent temporal record update. But the existence of temprol variables brought some unsertainty, even wrong on database operations, as well as the temprol relational algebra operations. Based on BCDM, binded the temporal variables, then defined the temporal relational by using the temporal mapping set, at last, established the temporal relational algebra system. The algebra system is close under the bitemporal operation.