PDDL：持续动作中效果和条件的确切含义

Question

在 PDDL 2.1 中，引入了 durative-action。它们（除其他外）用 conditons 和 effects 描述。两者都可以定义为 at start/at end、condition 也可以是 over all.

我找到了以下文档，相当广泛地描述了 PDDL 2.1：pddl2.1 : An Extension to pddl for Expressing Temporal Planning Domains。不过，我在获取确切含义时遇到了一些问题。

论文给出了如下例子：

    (:durative-action heat-water
        :parameters (?p - pan)
        :duration (= ?duration (/ (- 100 (temperature ?p)) (heat-rate)))
        :condition (and (at start (full ?p))
            (at start (onHeatSource ?p))
            (at start (byPan))
            (over all (full ?p))
            (over all (onHeatSource ?p))
            (over all (heating ?p))
            (at end (byPan)))
        :effect (and
            (at start (heating ?p))
            (at end (not (heating ?p)))
            (at end (assign (temperature ?p) 100)))
    )

我在想，(at start (onHeatSource ?p))是不是多余的，因为还有(over all (onHeatSource ?p))这个说法。如果不是，区别在哪里？

评估的顺序是什么？ condition at start、effect at start、effect at end、condition at end？ over all 是否包括时间实例 at start 和 at end？

Answer 1

您的问题实际上在您引用的同一篇文章中得到了回答。在第 12（或 72）页，您可以找到解释：

Invariant conditions in a durative action are required to hold over an interval that is open at both ends (starting and ending at the end points of the action). These are expressed using the over all construct seen in Figures 6 and 8. If one wants to specify that a fact p holds in the closed interval over the duration of a durative action, then three conditions are required: (at start p), (over all p) and (at end p).

所以我想没有什么需要解释的了。

关于你的第二个问题：

What is the order of evaluation? condition at start, effect at start, effect at end, condition at end? Does over all include the time instance at start and at end?

上一题之前回答过：over all是一个open区间。对于其余部分，即关于评估顺序的问题，我不明白这个问题——这对我来说似乎没有意义。条件是为了使操作适用而必须满足的条件。但与非持续性行为相比，这些标准不仅在应用它的特定状态下进行评估，而且在一系列状态下进行评估。这些条件适用于哪些状态由关键字 at start、at end 和 over all.

指定

效果未被评估，但它们"happen"，即它们指定结果状态（在at end中）如何因此而改变行动申请。

-- 希望对您有所帮助

PDDL：持续动作中效果和条件的确切含义

PDDL: Exact meaning of effects and conditions in durative-actions

planning

pddl