# RE: some basic questions, thanks

From: Zhu Bin <zhubin@cai.pku.edu.cn>
Date: Sat, 20 Sep 2003 15:46:34 +0800
To: <www-rdf-logic@w3.org>
Message-ID: <000001c37f4b\$50f564c0\$930e69a2@minc>
```I think you should distinguish the Ħ°subclassĦħ and the Ħ°equivalent
classĦħ, they are different.

-----Original Message-----
From: Li Qin [mailto:bethqin@hotmail.com]
Sent: 2003Äê9ÔÂ20ÈĠ 0:37
To: yzqu@seu.edu.cn; www-rdf-logic-request@w3.org; zhubin@cai.pku.edu.cn
Subject: Re: some basic questions, thanks

2. If fruit is the union of sweetfruit and nonsweetfruit, grape is the
subclass of fruit, does it mean that grape is the union of sweetfruit
and nonsweetfruit?
Being the union of other classes is not a property which can be
inherited by its subclasses, I think.
4. I mean, e.g. graduate student is a subclass of student. When do you
annotate someone as the instance of student instead of its subclasses?
own instances which are also instances of college student, does college
student have its own instances other than that?
>From: "Yuzhong Qu"
>To: "Zhu Bin" ,"Li Qin"
>Subject: Re: some basic questions, thanks
>Date: Fri, 19 Sep 2003 14:11:13 +0800
>
>Li Qin wrote:
>
>1. Intersection, as a set operation to get the common part of two sets,

>does not introduce any hierarchy at all. Here, if A is the intersection

>of B and C means that A is the subclass of B and C, this intersection
>introduces hierarchy.
>
>* The intersection of B and C can be understood as the greatest lower
bound of B and C.
>
>2. "If A is the subclass of union of B and C" does not mean that A is
>the union of B and C. My question concerns the case that A is the union

>of B and C.
>If A is the union of B and C, the instances of B and C are instances of

>A.
>If A is the superclass of B and C, the instances of B and C are
>instances of A.
>What is the difference?
>
>* The properties of a superclass are applicable to the instances of the
subclasses.
>
>3. If A is the complement to B, A is the difference between an unkown
>class and B. Does this unkown class the union of A and B or the
>superclass of A and B?
>
>* Just guess, use the union structure.
>
>4. When do you use a class instead of its subclasses for their
>instances, if they all have their own instances?
>
>* Sorry, I can't understand your question.
>
>5. If A is the union of B and C. What is the relationship between the
>instances of A, B and C?
>
>* Agree with Zhu Bin's point.
>
>
>
>Yuzhong Qu
>Dept.Computer Science and Engineering
>Southest University, Nanjing, China
>http://cse.seu.edu.cn/People/yzqu/en
>
>

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