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  1. #1
    Join Date
    Oct 2005
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    4

    Exclamation library database...help

    hi, need help, heres the senario, the questions are at the bottom, mainly need help with part (f), but a different perspective on (a)to(e) would be helpful


    University wishes to create/build a database to monitor its library. Consider the following requirements for the university library database:

    The library is organized into sections based on subject areas. Each section is identified by a code, has a name related to the subject area, a location, and a librarian responsible for the section (manager).

    The library is composed of books, Journals, and CDs located in different sections. Each book is described by a number, has a title, authors, version, year, edition, subject area, and location. A book can be classified either as a consultation only item or as a loan item. The books that can be borrowed have an associated maximum period for loan. The loan period is different for each type of user of the library. The library database maintains record of the total number of copies for a certain book and the number of copies that are on loan.

    Journals are for consultation only. Each journal is classified by a number and is described by title, volume, number, year, location, and related subject area. The CDs are also identified by a number. A CD can be of type music, computer game, or related to a periodic. Music and game CDs can be borrowed and have a title and associated singers/authors. The library database maintains record of the total number of copies for a certain CD. Periodic CDs are only for consultation and have a title.

    The library users include students, academics and university staff. Each user is unique identified by an ID code and name. They also have an address and telephone number. For each type of users there is a maximum number of items that the user of this type can borrow for a certain period of time. Information about an item that was borrowed need to be known at any point in time, including the date that the item was borrowed and the date that it is supposed to be returned. A fine of £0.75 per day is charged for each day that a user delays on returning an item to the library. Information about fines is registered for each related user.

    The library contains its own staff members (librarian). Each librarian is described by an ID Staff code, name, address, date of birth, sex, salary, function, and related working section. A librarian is allocated to a unique section.

    ----------

    (a)
    Identify the main entities in this description of the University’s requirements.

    (b)
    Identify the main relationships between entitles described in part (a), represent each relationship as an ER diagram, clearly labelling each relationship. Any many-to-many relationships should be included in your answer to part (b).

    (c)
    State the degree of each of the relationships described in part (b). Decompose any many to many relationships, replacing them with new entity types and relationships.

    (d)
    Identify all attributes and place them in a list, associating them with an entity or relationship.

    (e)
    Determine candidate key attributes, primary key attributes and foreign key attributes for each entity.

    (f)
    Using your answers (a) to (e), create a single Entity-Relationship (ER) diagram to represent the data requirements of the University database. To simplify the diagram, only show entities, relationships, primary and foreign key attributes. State any assumptions (if necessary) to support your design.


    thanks in advance

  2. #2
    Join Date
    Mar 2004
    Location
    Toronto, ON, Canada
    Posts
    513
    A word of advice - at least pretend you're not trying to get us to do your homework.

    jono
    --
    Jonathan Petruk
    DB2 Database Consultant

  3. #3
    Join Date
    Apr 2004
    Location
    Toronto, Canada
    Posts
    249
    I think that
    Using your answers (a) to (e),
    is a dead giveaway to the fact that you are asking us to do your homework.

    Please take the trouble to read your homework before you post it.

    By the way, we do not do your homework for you. Try another forum, please.

    Ravi

  4. #4
    Join Date
    Oct 2005
    Posts
    4

    Angry

    im not asking you to do my homework, if you actually read what i said, ive done most of it, im just having trouble with the last part u idiot!!!!!!!!!!!!!!!!!!!!! i included everything in the question so that who ever wanted to help would know the background infomation.

  5. #5
    Join Date
    Mar 2004
    Location
    Toronto, ON, Canada
    Posts
    513
    Well at least you're asking nicely...
    --
    Jonathan Petruk
    DB2 Database Consultant

  6. #6
    Join Date
    Oct 2005
    Posts
    4
    could you please stop wating my time, what is the point of you writting posts with no helpfull infomation regarding the thread?

  7. #7
    Join Date
    Apr 2004
    Location
    Toronto, Canada
    Posts
    249
    I did read the original post and these were my first reactions to it.

    He needs help on the last part. The last part depends on having done the first five parts. We do not see anything resembling his attempts at answering the first five parts. So how are we supposed to help him build the last part?

    If you had been kind enough to show what you had done for the first five, we would have had a more serious look at the problem and suggested a way or two to use the first five to help with the last part.

    Since you did not tell us what you had done for the first five parts, any attempt at helping you would have required us to do the first five parts anyway.

    Hence the comment that we do not do your homework for you.

    From now on, please post whatever you have done, and then somebody will be happy to help you.

    Ravi

  8. #8
    Join Date
    Oct 2005
    Posts
    4

    Red face

    i am sorry, im new to this forum thing, heres what ive got so far, my diagrams and tables have not copied very well, i hope you get the idea tho. however i do relise you will need the table at the bottom to create the final er diagram, it just shows the attributes of the entities to part (a) these listed attributes can also bee seen in my answer to part (c)

    ----------------------------------------------------------------------------------------------------------------------------------
    (a)

    An entity is any distinguishable object or concept that is to be represented in the database. Considering this, the following are the 'main' entities i have identified in the description of the University's requirments.

     Section
     Book
     Journal
     CD
     User
     Staff

    (b)
    After assuming i have selected the correct entities form the Universitiys describtion, the next step to indentify logical links between these entites and representing these links in an ER diagram. The reson for this is that later in the design process tables are created from the origonal entities. These relationships are what allow one table to access related information in another table. The diagrams below show the relation ships between the entities outlined in part (a) as required i have included the many-to-many relationships which will be resolved in my answer to part (c)



    The relationship between the entities Book and User is many-to-many. Books can be borrowed by many users & many users can borrow many books.



    Book User





    The relationship between the entities Library and Sections is one-to-many as the Library has many sections and the sections belong to only one library.



    Library Section






    The relationship between the entities CD and User is many-to-many. CD's can be borrowed by many users & many users can borrow many CD's.



    CD User




    As outlined in the University's description, Journals are for consutation only and cannot be loaned. For this reason there doesnot seem to be a logical link associated in a ER diagram between the Jornal and the User. Therefore i have made a logical link between Journal and section. Weather this is a 'main relationship' or just a link, i will include it at this stage. It can be discarded later if it reveiled not to be a 'main relationship'.
    This relationship between Journal and Section can be described as many-to-many, as many Journals can be in many Sections and many Sections can contain many Journals.


    Journal Section







    The relationship between Section and Staff is one-to-one as only one staff member is allocated to one section within the Library.


    Section Staff



    (c )
    Assuming i have included all the relationships required in part (b) below i have stated the degree of these relationships. The degree of a relationship is defined as the number of attributes a relationship contains.
    Also the definition states that the degree is a number For this reason I will list all the attributes of all entities in the relationship and a number which precedes the list convaying the degree of the relationship.


    (i) Book>User: 13 (book)number,title,subject,location,authors,versio n,year,edition. (user)ID code,name,address,telephone number, loan limit.
    (ii) Library>Section: 11 (library)section,book,journal,cd,user,staff. (section)code,name,subject,location,librarian.
    (iii) CD>User: 11 (CD)number,title,music/game,location,singer/author,number of copies, (User)ID code,name,address,telephone number,loan limit.
    (iv) Journal>Section: 11 (journal)number,title,subject,location,volume,year . (Section)code,name,subject,location,librarian.
    (v) Section>staff: 12 (section)code,name,subject,location,librarian. (staff)ID code,name,address,DOB,salary,function,related section.




    Next I will decompose the many-to-many relationships which were outlined in part (b) the reason for removing many-to-many relationships is because the relational data model doesn’t have the means for dealing with them, it only deals with one-to-one and one-to-many relationship






    Section Book Journal CD User Staff
    Code Number Number Number ID code ID code
    Name Title Title Title Name Name
    Subject Subject Subject Music/game Address Address
    Location Location Location Location Telephone No. DOB
    Librarian Authors Volume Singer/authors Loan limit Salary
    Version Year No. of copies Function
    Year Related section
    Edition

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