An application for the project is that to construct a forum
<List of entities and relationships (relationships are expressed by bold faces.)>
User : user starts to write one topic/user sends a message/user gives replies for one
topic/user receives a message
Admin : administrator is a special user.
Topic : topic follows reply / topic contains votes
Board : board contains many topics / board is managed by administrators
Messages : user sends message / user receives message
Vote: vote is based on topic
Reply : reply is followed by topics
<Kinds of Queries>
What is the user information of a selected topic?
How many boards in a forum?
How many topics in a selected board?
What is the latest topic?
How many topics have been started by user?
What is the board with most topics?
What is the topic that has most replies?
Is there a new message for someone?
What are the messages of a selected user?
What is the number of messages of a selected user?