I am developing Library Management System which have two sorts of books (Ebook and PrintedBook).
I intends to make search capacity with both ebook and printedbook in the same page.
The only problem is that I see that ebook and printedbook are book. And should I make an Book entity, and PrintedBook and Ebook inherits Book entity. If I do this, the search capacity is easier by using IBookRepository. If not I have to join two tables (Ebooks and PrintedBooks).
Please help me.
Dealing with inheritance at persistance level, esspecialy when talking about relation databases, can be a headache. First of all you should ask yourself why is this a problem for you.
If the problem is a performance due to using JOIN in you database query you might look at technique called single table inheritance. Basically you have one table containing all the columns of all your book types (i.e. PrintedBook and Ebook). This way you don't have to use JOIN, but you sacrifice some storage.
Other then the concrete table inheritanec technique (as described by yourself) there is no other way how to deal with the inheritance problem in relation databases.
If your application becomes too complex or the domain model isn't compatible with your read use cases, you might look at read-model. Read-model helps you to focus on your problem domain without modifying it while having easy access to the data. This is very complex topic so if you want to read something about read-models (or about DDD implementation problems/techniques) I recommend you to read Implementing Domain-Driven Design by Vaugh Vernon.
