Aliakbar Mohammadyari

7/17/2019 Aliakbar Mohammadyari

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Aliakbar Mohammadyari

Ch.5 Data and Process Modeling

Q. Describe data and process modeling concepts and tools

During the data and process modeling, a systems analyst develops

graphical models to show how the system transforms data into

useful information. Overall, these tools and modeling concepts

serve to make data and processes easier to visualize and

understand via diagrams (DFD), tables (Decision table), and charts

(decision trees). Data and process modeling involves three main

tools data !ow diagrams, a data dictionary, and process

descriptions. "ystems analysts use many graphical techni#ues to

describe an information system. $ data !ow diagram (DFD) uses

various symbols to show how the system transforms input data into

useful information.

Q. Explain the diferences between Gane and Sarson and

Yordon s!mbols. Pro"ide examples o# s!mbols that

represent processes$ data %ows$ data stores$ and entities.

Diference is the slight shape diferences between the symbols like

the rounding o the process symbol.

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Process %eceives input data and produces output that has a

di&erent content, form, or both

Data Flow $ path for data to move from one part of the

information system to another.Data Store 'sed in a DFD to represent a situation in which the

system must retain data.

External Entity $ person, department, outside organization, or

other information system that provides data to the system or

receives output from the system

Q. &hat is the diference between a context diagram and

diagram '( &hich s!mbol is not sed in a context diagram(

$ contet diagram describes a single big process whereas diagram

describes the small processes that are linked to a big single

process. *.g. if +% is a big process then its sub processes will be

number of sta& in each department, hiring process for each

department, payroll for each sta& member, benets for sta&

member, etc., that can also be further eploded into processes.

Data store symbols are not used in contet diagrams.

Q. )ow wold !o explode D*Ds(

DFD-s can be eploded by assigning one process as parent and

other as child processes. would eplode DFDs /oing down a level

and including more symbols and structures. *ploding Diagram 0

would reveal 0.0, 0.1, etc.

Q. Describe a data dictionar! and list the t!pes o#

in#ormation it contains.

2he data dictionary is a central storehouse of information about the

system3s data. t is used to collect, document and organize facts

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about the system. t is used to set up how data will be stored in

databases and what will be transferred from department to

department. $ll data elements, data !ows, data stores, processes,

entities, and records are documented in the data dictionary.

Q. )ow wold !o le"el D*Ds(

4ost general, lowest numbers and more specic5 higher numbers.

Q. )ow wold !o balance D*Ds(

*nsuring there are an e#ual amount of arrows going into and out of

every process as there was before.

Q. &hat is the prpose o# decision tables( )ow do !o

create them(

A decision table is a structured table o the combination o all the

conditions and outcomes that analysts can ace during a process. It

helps an analyst in keeping in consideration all the possible situation

that can occur during a process.

A decision table can be created by ollowing the ollowing steps:

1.Name the table by its process: Name o the process serves as a

heading and will come at the top.

.!nter the condition: "he conditions must be entered as one

condition per line and should come under the main process heading.

#.!nter the combination: a condition might have many

combinations. !nter all the combinations or each condition.

$.Accept or re%ect: &lace an ' in ront o each condition under each

rule (a rule is a numbered possibility in a column) to show the action

as re%ected or accepted.

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Q. &h! wold a manager pre#er a decision tree instead o# adecision table(

6ecause a decision tree is easier to visualize and includes more

detail.

Q. &hat is strctred English(

"tructured *nglish is a subset of "tandard *nglish that describes

logical processes clearly and accurately. 7ou must conform to the

following rules

0. 'se only three building blocks of se#uence, selection, and

iteration.

1. 'se indentation for readability,

8. 'se a limited vocabulary, including standard terms used in the

data dictionary and specic words that describe the processing

rules.

Case Stdies

.

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• +itchen Gadgets

• *itchen +adgets sells a line o high,-uality kitchen utensils andgadgets. hen customers place orders on the company/s ebsite or through electronic data interchange (!DI)0 the systemchecks to see i the items are in stock0 issues a status message

to the customer0 and generates a shipping order to thewarehouse0 which lls the order. hen the order is shipped0 thecustomer is billed. "he system also produces various reports.

•

● ,as-s

• ist #or elements sed in D*Ds$ draw the s!mbols$ andexplain how the! are sed.

• 2he four elements are eternal entity (the original source ofdata or the receiver of information), process (a series of steps

that manipulate data), data store (place to keep data for lateruse), and data !ow (describes the data and the informationelements passing between eternal entities, processes, anddata stores).

● Draw a context diagram #or the order s!stem.

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● Draw a diagram ' D*D #or the order s!stem. Explode E/C)

process 01st once2 to create a le"el 3 diagram$ E/C)4

Ensre it is balanced4

Chapter Case College Dri"er 6nsrance

.

7ac-grond "he company uses several actors to set discounts0 as ollows:

• A student who has taken a sae driver course earns a 23

discount.

• A student with a clean record (no tickets or accidents in the last

three years) earns a 23 discount.

•

A student who is # or older earns a 23 discount• A student who meets all three conditions(has taken a sae driver

course and has a clean record and is #)earns an additionalbonus discount o 23.

,as-s● Create a decision table that describes the discont rles.

Conditions 1 2 3 4 5 6 7 8

Student taken a safe drive course Y Y Y Y N N N N

Student with a clean record Y Y N N Y Y N N

Student is 23 or older Y N Y N Y N Y N

Elii!le to 5" #iscount $ $ $ $ $ $ $Elii!le to 5" %onus discount $

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&nelii!e to discount $

● Simpli#! the table !o 1st created. Describe the reslts.

Conditions 1 2 3 4 5 6

Student taken a safe drive course Y Y Y N N NStudent with a clean record Y Y N Y N N

Student is 23 or older Y N ' ' Y N

Elii!le to 5" #iscount $ $ $ $ $

Elii!le to 5" %onus discount $

&nelii!e to discount $

● Draw a simpli8ed decision tree that shows the discontrles.

Q. &hat are the pros and cons o# sing a decision table"erss a decision tree(

9hether to use a decision table or a decision tree often is a matterof personal preference. $ decision table might be a better way tohandle comple combination of conditions. On the other hand, a

decision tree is an e&ective way to describe a relatively.

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9e#erences

1, 4ystems Analysis and Design , 5th edition0 Alan Dennis

, 4ystems Analysis and Design 6ethods0 7efrey hitten0 8onnie

9entley

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