dia：在 Chen 的表示法中，什么是点边框 atts，什么是多值 atts？
我正在查看 
，我觉得我知道发生了什么，直到看到“PlayersIn< /code>”和“树叶”。叶子是一个双线边框属性，因为它是多值。这意味着什么？它在实际的数据库查询中看起来如何？我不知道“PlayersIn”虚线边框表示什么。您能否解释一下它的含义以及何时有用？它是什么意思，查询是什么样的，为什么它很重要，等等？
I'm looking at , and I feel like I know what's going on until I see "PlayersIn" and "Foliage". Foliage is a double-line-bordered attribute because it is multivalued. What does that mean? How does it look in an actual database query? I don't know what the "PlayersIn" dotted-line bordering indicates. Can you please explain what it indicates, and when it is useful? What does it mean, what does a query look like, why is it important, etc.?
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*重要提示：链接包含 java，但它们是 .ca 网站，因此可能是安全的。
Foliage是多值的，我仍然不确定为什么有人会想要这样做。我读了一些文档，这里，关于 Chen Notation，内容如下： “您可能希望将学位存储在多值字段中，以表明某人拥有多个学位，例如学士学位和硕士学位。”我不明白为什么学位类型的外键不与依赖表employeeID x DegreeID一起使用？也许是因为只有一张桌子不那么混乱？就“树叶”而言，我想，“也许树叶有很多种，对人们来说并不重要。”也许使用多值字段会更快，因为不需要连接。至于黄色的点边框属性，它是一个
派生属性。派生属性是可以通过解析其他属性获得的属性。有时，列出派生属性似乎是为了方便人们。我不确定这是否只是一个优雅的问题，或者这是否可以以某种方式加快代码速度。*Important note: the links contain java, but they are .ca websites and therefore likely secure.
Foliageis multi-valued, and I'm still unsure why anyone would want to do that. I read some documentation, here, on Chen Notation, that say: 'You may want to store degrees in a multi-value field, to show that someone has more than one degree, like a BA and an MS.' I don't understand why a foreign key for degree types isn't used with a dependency table,employeeID x degreeID? Maybe because it's less confusing to have only one table? As far as 'foliage' is concerned, I thought, 'Maybe there are many kinds of foliage, and it's unimportant to people. Maybe it's faster to use a multivalue field because joins are not necessary.'As far as the yellow, dot-bordered attribute, it's a
derived attribute. Derived attributes are attributes which can be obtained by parsing other attributes. Sometimes derived attributes are listed for human convenience, it appears. I'm not sure if it's only an issue of elegance, or if this can somehow speed the code up, though.