一句话:为定量等式逻辑引入不动点扩展,在定量代数中给出近似相等语义,并刻画收敛速率与 Conway/迭代理论。
本文为定量等式逻辑(quantitative equational logic)发展了不动点扩展。与以往在度量空间中处理精确相等的不动点工作不同,作者采用近似相等这一更适应定量场景的概念,语义建立在一有界完全定量代数上。由此得到一种新的不动点理论:它不仅能求解传统的不动点方程,还能定义向不动点的收敛速率。作者证明该理论是 Conway 理论的定量类比,也是迭代理论的定量类比,并且反映了度量余归纳原理。作为示例,他们研究了 Markov 决策过程的 Bellman 方程。该工作将不动点、代数理论与定量语义统一起来,为定量等式推理提供了新工具。
We develop a fixed-point extension of quantitative equational logic and give semantics in one-bounded complete quantitative algebras. Unlike previous related work about fixed-points in metric spaces, we are working with the notion of approximate equality rather than exact equality. The result is a novel theory of fixed points which can not only provide solutions to the traditional fixed-point equations but we can also define the rate of convergence to the fixed point. We show that such a theory is the quantitative analogue of a Conway theory and also of an iteration theory; and it reflects the metric coinduction principle. We study the Bellman equation for a Markov decision process as an illustrative example.