Question

I have the following domain, a dossier with documents:

-Dossier(Name,Documents[])
-Document(Name)

Now there is a new requeriment for a few dossiers which have subjects and each subject has documents, so the new domain would be like this:

-Dossier(Name,Subjects[])
-Subject(Number,Documents[])
-Document(Name)

For these few dossiers (7%) , I have to change a simple design for a more complex design. My question is: There is a design pattern or any idea which I can use for support the subjects but avoiding to change the initial domain.

Answer 1

I think you are looking for the Decorator Pattern.

You may also find the Composite Pattern or the Delegation pattern useful here.