[answer] should the role with one end of the reflexive association be called "current version"

The fifth element 2022-1-13 20:23

Mr. Pan , What is the analysis mode of this historical version , Should it be Last version and current version , Not the next version ？

( It seems strange that an organization has a version of reflexive Association , But there is a story behind it , And this is an intermediate result , Let's not expand here .—— Here is a supplementary note , Not the original Q & a content .)

UMLChina Pan Jiayu

what “ current version ”, You confuse classes with objects .

“ current version ”“ own ” You may think that reflexive association is an object's own , In fact, reflexive association also has two objects , Only two objects belong to the same set .

Do you think , If so , All reflexive associations should have a multiplicity at one end that is strictly “1”, because “ own ” There is only one .

Class diagrams are about mapping rules

for example ,

Organizations and people have a one to many relationship of employment , organization 1, Lots of people , intend ：

For an organization object in the organization collection , It may employ more than one person in the person set

For a personnel object in the personnel collection , There may be... In the organization set 1 Organizations employ it

Empathy

An organization has a one to many relationship between its parent and child , The superior 1, Multiple subordinates , intend ：

For an organization object in the organization collection , There may be multiple subordinate organizations in the organization set

For an organization object in the organization collection , There may be... In the organization set 1 Parent organizations

Writing code can be

class organization

{

organization The superior ;

List< organization > subordinate ;

......

}

Of course , image 1 Reflexive association to many , You can leave only one superior , When you need to find a subordinate, you can calculate the subordinate .