首页 > 笔记, 逻辑, 语义网 > 笔记:加注(Annotated) RDF (3) Dekhtyar 2001

笔记:加注(Annotated) RDF (3) Dekhtyar 2001

Alex Dekhtyar, Robert B. Ross, V. S. Subrahmanian: Probabilistic temporal databases, I: algebra. ACM Trans. Database Syst. 26(1): 41-95 (2001)

正文44页,共67页。

背景:这个似乎和Annotated RDF无关。不过,temporal information是一种最常见的annotation,而在tuple上的工作,自然也可以用在triple上。Alexander Dekhtyar是Subrahmanian 2000年毕业的PhD。后面的APT (Annotated Probabilistic Temporal) Logic [Shakarian 2011]看似是这个工作的扩展

基本建模对象:Data tuple d is in relation R at some point of time in the interval [ti, tj ] with probability between p1 and p2. 例:

  • Package p will arrive in Albany at some time between 9am and 5pm on Nov. 8 with probability 50–60%
  • Rain is expected to begin sometime between 2pm and 12 midnight on Nov. 8 with probability 5–20%
  • IBM stockwill reach $300 per share some time during the time
    interval Nov 1-10 with probability 90-100%

时间的模型:文中Fig 1 普通数据库,时态数据库和概率时态数据库的区别

  • Time Unit: 比如天 day={1,2,…,31}
  • Linear hierarchy of time units: 比如 day < month < year
  • Time point: 是一个tuple,每个分量来自hierarchy中的一层,例如(2011 May 7 Sat 18 28)
  • Calendar: 规定了time point的合法性,比如(2011 Feb 31)是不合法的
Temporal constraint: 基本的约束是形如day >= 5 或者 (2011 May 1 ~ 2011 May 7) 【注,原文要求(t1 ~ t2)里t1晚于t2,反直觉】。复杂的约束由基本约束通过 与∧ 或∨ 非¬ 构造。例 (year=1996 ∧ month < 4)
【待续】
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