Relational queries computable in polynomial time

Q4 Mathematics 信息与控制 Pub Date : 1986-01-01 DOI:10.1016/S0019-9958(86)80029-8
Neil Immerman
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引用次数: 728

Abstract

We characterize the polynomial time computable queries as those expressible in relational calculus plus a least fixed point operator and a total ordering on the universe. We also show that even without the ordering one application of fixed point suffices to express any query expressible with several alternations of fixed point and negation. This proves that the fixed point query hierarchy suggested by Chandra and Harel collapses at the first fixed point level. It is also a general result showing that in finite model theory one application of fixed point suffices.

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关系查询可在多项式时间内计算
我们将多项式时间可计算查询描述为关系演算中可表达的查询加上最小不动点算子和全域上的全序。我们还证明了即使不动点没有排序,一个不动点的应用也足以表示任何具有不动点和否定交替的可表示查询。这证明了由Chandra和Harel提出的不动点查询层次结构在第一个不动点层次上是崩溃的。这也是证明在有限模型理论中,不动点的一种应用就足够的一般结果。
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来源期刊
信息与控制
信息与控制 Mathematics-Control and Optimization
CiteScore
1.50
自引率
0.00%
发文量
4623
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