Symbol s

The passage around this formula

…list, a delete list, and an add list, and used a resolution theorem prover guided by means-ends analysis to search for a sequence of operators connecting the current state to a goal state [ 2 ] . Formally, for a state s represented as a set of ground predicates and an operator a with precondition set $\mathrm{pre}(a)$ , delete set $\mathrm{del}(a)$ , and add set $\mathrm{add}(a)$ , the operator is applicable when its preconditions hold, and produces a new state by $\mathrm{pre}(a) \subseteq s \;\Longrightarrow\; \delta(s,a) = \big(s \setminus \mathrm{del}(a)\big) \cup \mathrm{add}(a)$. This is worth writing out because…

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