This system manages the information of a college library
y
The library has good collection of books, magazines, and its issued to readers who work in departments.
y y y
The books and magazines are two main entities in this system and they are issued to reade The readers belong to departments and they are given unique reader numbers
The books and magazine collections are given unique tickets to keep track of to whom they are issued.
y
The entity relationship between these entities is as follows.
Books
Collections
Languages
# coll_no
#book_no
#lang_no
* Not null
*book_name
*lang_name
*size *time_publ *year_ publ Specialty
author
*Spec_name
chief_author comp_auth *lang_no
#dept_no *dept_name
*lang_sys
cost
#spec_no
Department
*lang_vn
Nations
*nation_no
#nation_no
*spec_no
*nation_name
*coll_no
*nation_vn
kw_master kw_slave comment
Readers #reader_no
B/r book tickets
*reader_name
#reader_no
Comment #primary key * not null
Collections
Magazine Header
Languages
# coll_no
#magazine_head_no
#lang_no
* Not null
*mag_name
*lang_name
*start_year imag_shefl issue_no Specialty
*lang_vn *lang_sys
pub_house
#spec_no
*lang_no
*Spec_name
*nation_no *spec_no *coll_no comment
Nations #nation_no *nation_name
Department
*nation_vn
#dept_no *dept_name
Readers #reader_no
B/r maga tickets
*reader_name
#reader_no
*dept_no
Comment #primary key * not null
y
The main information management system can be described by the context level diagram.
y
The information about the document suppliers through whom the magazines and books ar purchased is stored in the system.
y
This is validated and maintained by the system.
y
Any book that arrives, its payments, entry into the library is dealt with by the system.
y
Then the book is ready to be borrowed by the readers.
y
The readers from various departments are validated and they are issued the book borrowi ticket through the system.
y
If the is returned then its ticket entries are accordingly updated by the system.
y
The system generated various re[orts that have to be produced for management purpose.
Ex1 At first we have to identify all actors. In this case I think they are self reve aling : y y y
Employee Manager Administrator
Then we should identify y y y y y y
what w ill they
do.
reserve a room review reservation status cancel reservation edit holiday home data edit ciphers login
Now we just have to link this together. We use generalization between actors as manager has the same use case employee and administrator has the same as manager plus he can edit ciphers.
DFD Example - General model of publisher's present ordering system
Following are the set of DFDs drawn for the General model of publisher's present ordering system.
First Level DFD
S econd
Level DFD - Showing Order Verification & credit c heck
T hird
Level DFD - Elaborating an order processing & s hipping
Ex 2
An example of a Data Flow Diagram - DFD for a system that pays workers is shown in the figure below. In this DFD the is one basic input data flow, the weekly time sheet, which originates from the source worker. The basic output is the pa check, the sink for which is also the worker. In this system, first the employee's record is retrieved, using the employee which is contained in the time sheet. From the employee record, the rate of payment and overtime are obtained.
These rates and the regular and overtime hours (from the time sheet) are used to complete the payment. After total payment is determined, taxes are deducted. To computer the tax deduction, information from the tax rate file is used. T amount of tax deducted is recorded in the employee and company records. Finally, the paycheck is issued for the net The amount paid is also recorded in company records.
Ex 3 Chinese Takeaway
The example below is an illustration of the data flow in a takeaway restaurant. The order is taken on a carbon pad, the cost is calculated from the menu, and the order is checked with the customer, if OK the order is stuck on a pin-board. When the food is ready, the order becomes the delivery note for the driver. At the close of business, carbons are used to update accounts and then dumped along with the delivery notes. Management information is passed to the manager.
