prolog – 如何理解ASP中的否定失败？

human(socrates).
day(tomorrow).
die(X) :- human(X).
may_go_to_school(Y) :- day(Y),not holiday(Y).

如果我们运行clingo来获取程序的答案集,我们就会得到

Answer: 1
human(socrates) day(tomorrow) die(socrates) may_go_to_school(tomorrow)

我们知道地滚球将首先将所有变量实例化为常数,因此接地后的程序将是：

human(socrates).
day(tomorrow).
die(socrates) :- human(socrates).
may_go_to_school(tomorrow) :- day(tomorrow),not holiday(tomorrow).

我在book from Gelfond读到它给出了3条规则来获取答案集：

1. Satisfy the rules of Π. In other words,believe in the head of a rule if you believe in its body.

2. Do not believe in contradictions.

3. Adhere to the “Rationality Principle” which says: “Believe nothing you are not forced to believe.”

在规则中：

may_go_to_school(tomorrow) :- day(tomorrow),not holiday(tomorrow).

我们得到了一个否定,因为失败不是假期(明天)

如本书所示：

Symbol not is a new logical connective called default negation,(or negation as failure); not l is often read as “it is not believed that l is true.” Note that this does not imply that l is believed to be false. It is conceivable,in fact quite normal,for a rational reasoner to believe neither statement p nor its negation,?p.

然后根据规则1,如果你相信它的身体,相信一个规则的头,我是否应该相信身体不是假期(明天).既然我不相信任何假期(明天).也不是明天(明天).

根据答案,我应该相信?holiday(明天).

>那么为什么我们需要这种否定作为失败？
>我们可以使用经典否定吗？