问题描述
我正在使用Protégé4.0和Pellet 2.2学习OWL 2.0，并且试图逐步理解基本概念.
I'm learning OWL 2.0 using Protégé 4.0 and Pellet 2.2, and I'm trying to understand underlying concepts progressively.
因此，从类层次结构开始，我将一个类"Cat"作为子类Of"Things".
So, starting with class hierarchies, I made one class "Cat" as a SubClassOf "Things".
如果我启动Pellet，一切正常，但是如果我对猫"进行DL查询，则我的Directsubclasss"Nothing"和Subclasss"Nothing"都显示为红色.
If I start Pellet, everything works fine, but if I DL query "Cat", I have Directsubclasses "Nothing" and Subclasses "Nothing" appearing in red.
- 这是什么意思?
- 为什么红色?
正当化就像:
Explanation for: Nothing SubClassOf Cat
<Entailment1252345325436>SubClassOf Nothing and (not (Cat))
- 这是什么意思?
- 为什么这些蕴含"理由无穷无尽(我的意思是我只创建了1个类).
- 为避免这种现象，我必须纠正一个错误吗?还是我不在乎呢?
谢谢^ _ ^！
推荐答案
没有是空类，有时写为⊥.以DL表示法.在大多数情况下，如果您的类等效与 Nothing 无关，则是建模错误.例如，如果您不小心定义
Nothing is the empty class, sometimes written as ⊥ in DL notation. In most cases, if you have a class that's equivalent to Nothing, it's a modeling error. E.g., if you accidentally define
汽车EquivalentClass(拥有准确的2个门)
汽车EquivalentClass(拥有准确的4个门)
Car EquivalentClass (hasDoors exactly 2)
Car EquivalentClass (hasDoors exactly 4)
您会发现Car现在等于 Nothing ，因为某些东西不能恰好具有2个门和4个门.那是一个事故.逻辑上没有什么不对，但是通常通常您不希望您的类必需为空.因此，Protege必然会用红色显示空的类.
you'll find that Car is now equivalent to Nothing because something can't have exactly 2 and exactly 4 doors. That's an accident. There's nothing logically incorrect with it, but usually you don't want your classes to necessarily be empty. So, Protege shows necessarily empty classes in red.
当然，空类 Nothing ， 是每个类的子类，就像空集是每个集的子集一样，它必然是空的.
Of course, the empty class, Nothing, is a subclass of every class, just like the empty set is a subset of every set, and it's necessarily empty.
因此，您所看到的实际上没有任何错误. 没什么应该是红色的，并且应该是每个类的子类.一切都按照应有的方式进行.
So, there's actually nothing wrong with what you're seeing. Nothing should be red, and it should be a subclass of every class. Everything is working the way that it should.
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