Some really confusing things about parent-child relationship
Date: Tue, 14 Aug 2007 11:15:04 -0700
I would really need some help with the following questions. And
apologies for so many of them
That an instance A of parent class can have connections to several
instances of certain subclass, or that an instance A can have
connections to two or more instances, where each instance is of
different subclass type, or both?
In hierarchical model parent class can have several subclasses. What does that mean exactly?
That an instance A of parent class can have connections to several instances of certain subclass, or that an instance A can have connections to two or more instances, where each instance is of different subclass type, or both?
And why do we name some classes subclasses and other classes parents?
It makes sense in object oriented programs, but here subclass doesn't necessarily suggests more specialized version of parent class. As far as I understand it, in hierarchical model we get a parent child relationship by simply creating a connection between two classes?!
with network model child classes can have several parent classes --> do we call this a M:N connection, or does M:N connection only mean that an instance of certain child class is connected to several instances of certain parent class and vice versa?
Are in all three cases situations allowed where a child can have several parents?
Next comes the mother of all confusing statements: book starts claiming that between the two entity types there can be several 1:N connection ( meaning just 1:N connections ... M:N connections ).
Huh, didn't it previously claimed that complex network model allows M:N connections?
thank you Received on Tue Aug 14 2007 - 20:15:04 CEST