Chapter 4

Mailing program changes

› Requirement: Customers will Remain on the

mailing list if any below conditions are true

Requested a catalog

Ordered from SWL in the last two years

Signed guest-register on the Web site

› Requirement: Customers will be given a special discount certificate if they have

registered on the Web site

This table contains all the possible rules

Redundant or improperly grouped

Can be significantly reduced

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Requests catalog Y N Y Y Y N Y Y Y N N N Y N N N

Placed order in past two years Y N Y Y N Y Y N N Y Y N N Y N N

Signed guest register on website Y N Y N Y Y N Y N Y N Y N N Y N

Registered on website Y N N Y Y Y N N Y N Y Y N N N Y

Remain on mailing list X X X X X X X X X X X X X X

Remove from mailing list X X

Receive discount certificate X X X X X X X X

Reduced rules by approx. 75%

Still contains all possible results

All 4 conditions are not related and

further reduces the size of the table

1 2 3 4 5

Requests catalog Y - - N -

Placed order in past two years - Y - N -

Signed guest register on website - - Y N -

Registered on website - - - - Y

Remain on mailing list X X X

Remove from mailing list X

Receive discount certificate X

Graphical representation of Decision

Table

› The first tree represents the conditions:

Request catalog

Placed order in past two years

Signed guest-register on website

› The only output we are concerned with is if

the customer data remains on the mailing list

or is removed

Customer requests catalog

Placed order in two

years

Signed guest

resister

Remove from

mailing list

Remain on mailing list

N

N

N

Y

Y

Y



This condition has no effect on the

previous conditions

› It is represented as a separate decision

because the out comes of either on have no effect on the other

YCustomer Registered on Website

Do nothing

Give discount

certificate

N

A third way to represent this kind of data

› First step is to identify what your input and

out put terms are

Input data flows:

› CUSTOMER

› CATALOG REQUEST

› ORDER LAST TWO

› SIGNED WEB-REGISTER

› REGISTERED

Output data flows

› REMAIN ON LIST

› REMOVE FROM LIST

› DISCOUNT CERTIFICATE

› DO NOTHING

After these are defined it is simple to

write out the structured English

expression

For each customer,

If CATLOG REQUEST = Y

Output REMAIN ON LIST

Else

If ORDER LAST TWO = Y


Else

If SIGNED WEB-REGISTER = Y


Else

Output REMOVE FROM LIST

If REGISTERED = Y

Output DISCOUNT CERTIFICATE

Else

Output DO NOTHING

Sequential tasks

1. Draw a context diagram

2. Draw a Diagram 0 DFD

3. Draw lower level diagrams

4. Work on functional primitives

Tasks 2-4 can be worked on simultaneously,

but must have at least one lower numbered

task to build off of

Concurrent tasks Can be completed at anytime because they

are not dependant on other tasks

1. Identify Processes

Receives input and produces output

2. Identify Data Flows

Input and output

3. Identify Data Stores

Data that needs to be saved

Concurrent tasks (cont)

4. Identify Entities

Things outside the system that provide input

or receive output

5. Create and Maintain a Data Dictionary

Central storehouse of information about a

system’s data

6. Revision and Editing

Checking for errors and inefficiancies

Some concurrent task must be

completed before a sequential task may

be completed

› (i.e.) any of the identification tasks, but these

task will occur throughout the entire process

Sports

Chapter 4