Go4Expert - Java classes help

Hello!

I have a project in which I must simulate a blog application,with users' post mangament.
These are the requirements:

A blog has a title and a collection of posts.The posts have the following information:

-author
-data
-title
-text

Each post has a code thet is generated automatically and which acts like the serial number within the speciality the post belongs to.
The speciality are:

-Information:This's a post with just text and an answer is forbiden.
-Version: It's a post of an information's version that gets updated.
-Debate: this's a post containing information and accepts one or more answers.
-Answer: It's an answer to a specific debate.

The program must support the following operations:

-Ask for User login identification(no password involved) to later use as the author of given posts.
-showing information about posts.
-create new posts.
-create new blog.
-store blog in hard drive.
-load blog.

Here are my classes:

Code:

abstract public class Post 

{

   private Date date;

   private String author;

   private String title;

   private String text;

   private int code;

    



}



public class Infor extends Post 

{

   

    Version ver;

}



public class Version extends Post 

{

   



}



public class Debate extends Post 

{

    Answer ans;

    Version vers;

}



public class Answer extends Post 

{

   

}

public class Debate extends Post 

{

    String btitle;

    Post pst;

}



public class Answer extends Post 

{

   

}

public class Debate extends Post 

{

    String btitle;

    Post pst;

}

Does this look ok?Does it need any more specification?
Any help is very appreciated!