在 OWL-DL 本体中,考虑具有域 D 和范围 R 的属性 p,其中 D 对 p 有一个限制,以具有恰好为 1 的基数:
D SubClassOf p exactly 1 Thing
- (D ⊑ =1 p.Thing)
那么我们是否可以推断 p 是一个函数属性,因为每个 D 类型的 d 将只有一个 p 值?如果这是正确的,推理者可以推断出这些知识吗?
最佳答案
在 OWL 中,当每个人最多有一个属性值时,属性就是函数。 “至多”很重要;允许某物对属性(property)没有值(value)。 (这意味着 OWL 中的函数属性实际上更像是数学中的可能偏函数。)也就是说,如果每个人对一个属性只有一个值,那么它显然最多只有一个属性值,所以正如您所怀疑的那样,属性(property)将是功能性的。然而,我们可以通过一个特定的案例来确保这是一般的,因为我们需要确保这里的属性 p 实际上对于每个人最多只有一个值。
Proof: Suppose the property p has domain D, and D is a subclass of =1 p.Thing, so that every D has exactly one p value. Is it the case that every individual x has at most one value for p? There are two cases to consider:
- x is a D. Then by the subclass axiom with the restriction, x must have exactly one value for p, and one is less than or equal to one.
- x is not a D. Then x has no values for p. If it did, then it would be in the domain of p, which is D, and that is a contradiction. Then x has zero values for p, and zero is less than or equal to one.
Then any individual x at most one value for the property p, which is the definition of p being functional. Thus, p is functional. QED
OWL DL 推理器应该能够确认这一点,并且应该不难检查。
关于semantic-web - 具有精确基数的属性是一个函数吗?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/26325341/