Kouramajian V, Fowler J
Office of the Vice President for Research & Information Systems, Rice University, Houston, Texas 77251.
Proc Annu Symp Comput Appl Med Care. 1994:315-9.
Recent research has focused on increasing the power of medical information systems by incorporating time into the database system. A problem with much of this research is that it fails to differentiate between historical time and future time. The concept of bitemporal lifespan presented in this paper overcomes this deficiency. Bitemporal lifespan supports the concepts of valid time and transaction time and allows the integration of past, current, and future information in a unified model. The concept of bitemporal lifespan is presented within the framework of the Extended Entity-Relationship model. This model permits the characterization of temporal properties of entities, relationships, and attributes. Bitemporal constraints are defined that must hold between entities forming "isa" hierarchies and between entities and relationships. Finally, bitemporal extensions are presented for database query languages in order to provide natural high-level operators for bitemporal query expressions.
最近的研究集中于通过将时间纳入数据库系统来增强医学信息系统的功能。这项研究中的许多问题在于未能区分历史时间和未来时间。本文提出的双时态寿命概念克服了这一缺陷。双时态寿命支持有效时间和事务时间的概念，并允许在统一模型中集成过去、当前和未来的信息。双时态寿命的概念是在扩展实体-关系模型的框架内提出的。该模型允许对实体、关系和属性的时间属性进行描述。定义了双时态约束，这些约束必须在形成“isa”层次结构的实体之间以及实体与关系之间成立。最后，为数据库查询语言提供了双时态扩展，以便为双时态查询表达式提供自然的高级运算符。
