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Mechanical Assignment

MovieExchange 代寫swapping site for movie buffs

1
MovieExchange
Overview
, which allows users to share DVDs with other people
across Australia.  It will be free to join and use.  All that users will pay to share their movies is postage in
one direction.  Unlike other trading websites, users will be swapping unwanted DVDs directly with other
users and not for credits or real currency.  High trust among the registered users of MovieExchange is
required.
 
Users will register and set up two lists of movie titles.   The first is their “Offer List” and contains all the
DVDs they own and are prepared to swap.  The second is their “Want List”, which has the movies they don’t
have but are interested in watching.
 
For any given user, the system will match the user’s items that are available to swap with people who have
DVDs that this user might want and alert the users accordingly.  It is then up to both parties to post their
DVDs to each other.
Detailed Requirements
MovieExchange will be a web application, utilising a MySql database.
 
Users
 
Only registered users of MovieExchange will be allowed to use the site.  Access to the system is via a
username and a password.  During registration, the system also records each user’s first and last name, and
their postal address, consisting of street, suburb, state and postcode.  Registered users must be able to update
this data on the website.
 
MovieExchange users must be able to maintain two lists of movie titles, known as the “Offer List” and the
“Want List”.  As the names suggest, the former is where users list the movies they have and are happy to
give away while the latter is where they tell what movies they are interested in seeing.
 
MovieExchange users trade (or swap) DVDs with each  other by sending them through the mail.  After a
swap, each party can rate the other party on a scale of -3 (poor) to +3 (outstanding).  The purpose of the
rating mechanism is to reward those who act in a timely fashion.  The higher a user’s rating, the higher the
chance others will want to trade with them.  Ratings are available on the site for all members to see.
 
Movies
 
To facilitate the addition of movie titles to the two lists, MovieExchange Pty Ltd have decided to maintain a
database of movies.  Several aspects of movies should be stored: movie title, year of release, classification
(PG, MA, etc.), genre (comedy, action, children, etc.), director, writer, and up to 3 actors.
 
For some time now, MovieExchange Pty Ltd has been building up their movie collection.  So far the data –
covering some 4,000 movies – has been collected in a large spreadsheet.  While each movie in the
spreadsheet always has information about the title, year of release and genre, sometimes other information
such as the director, the writer, and even sometimes members of the cast have not been entered as it was
unavailable.
 
The requirement is to model the movie data in a set of tables.  The system should offer the ability to search
for a movie by a keyword from its title, by genre, and/or by the name of an actor, the director or the writer. 
A list of movies meeting the search criteria will be returned.  From this list it should be possible to add a title
to the “Offer List” or the “Want List”.
 
  2
Trading
 
The trading (or swapping) concept is at the heart of MovieExchange.  The process is to operate as follows.
 
(1) Identify trades.  Registered users have the ability to search for potential trades.   This is to be done via a
query which takes everything on the user’s “Offer List” and checks which other MovieExchange members
have any of those items on their “Want Lists”.  The contents of the matched users’ “Offer Lists” are then
retrieved.  This represents everything a user could potentially get in exchange for one of their DVDs and all
the users they can get it from.
 
(2) Initiate trade.  The user (UserA) can then initiate a swap with another user (UserB).  In general, UserA
will choose who to swap with based on UserB’s rating and location.
 
(3) Complete trade.  When UserB logs in, they will see that UserA has initiated a swap with them.  If UserB
is happy to proceed, they will post their DVD to UserA.  This will be brought to UserA’s attention next time
they log in – and serve as a prompt for UserA to post their DVD to UserB.  After a few days, UserA will
receive UserB’s DVD and UserB will receive UserA’s.  Each party will then rate the other.
 
MovieExchange Pty Ltd would like the system to track the progress of each swap.  They have indicated that
the following 7 states will be sufficient for this purpose:
 
1.  Requested by UserA
2.  Responded by UserB (Accept)
3.  Responded by UserB (Declined)
4.  Sent by UserA
5.  Sent by UserB
6. Received by UserA
7. Received by UserB
 
A trade begins its life in state 1, “Requested by UserA”.  From state 1, the trade may move to state 2 or state
3, when UserB responds to the request.  If UserB declines (state 3), then the trade terminates. Otherwise
(state 2), the trade proceeds to states 4 and 5 where each of the two parties posts the DVD requested by the
other. Each party will indicate on the website when s/he has posted the requested DVD.
 
Depending on who receives the requested DVD first, the state may change to 6 (if UserA receives first) and
then to 7 (UserB receives second); or to 7 (UserB receives first) and then to 6 (UserA receives second).
Again, each party will indicate on the website that they have received their movie.
 
A trade is successful when states 6 and 7 are reached.
 
In order to minimise the potential for mix ups, MovieNet Pty Ltd require that while a swap is in progress, the
two DVDs being exchanged are “marked” as unavailable in the members’ Offer and Want Lists, so that no
other members may request to trade those DVDs.
 
The Current Situation
MovieExchange hired a consultant from Models-Are-Us who designed a data model for the application and
have implemented this data model in a MySQL database.  The scripts to create the database and insert data
into this database are available for you to download  so that you can create a copy of the database on your
own computer.  Also the data model produced is available and is shown on the  next page.  Before the
consultant could finish the implementation of the database, however, they were called away on a family
emergency, leaving the database unfinished in terms of being able query the data.  As such your job is to
generate the required SQL statements to handle  the queries required by the MovieExchange site.  A list of
these queries is found in the document “Assignment2 Task” available in the assessment link on the
LMS.
  3
 
 
Figure 1 : ER Model of System
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