Module 7

Prof. V.Rajaraman
System Analysis and Design
System Analysis and Design/Data Oriented Systems Design
Learning Objectives
Learning Objectives
The Entity-Relationship(ER) modeling to develop a conceptual model of data.
How to organize data required in an application as relations.
The need for normalizing relations.
The various normal forms and their relevance.
How to normalize relations to successive higher normal forms to form a relational database.
The need for an integrated database in organizations.
The goals of Data Base Management systems (DBMS).
The structure and organization of DBMS.
V. Rajaraman/IISc. Bangalore
Indian Institute of Science Bangalore
//V1/June 04/1
Prof. V.Rajaraman
System Analysis and Design
System Analysis and Design/ Data Oriented Systems Design
Motivation
Motivation
When a DFD is developed we have knowledge of all data elements required by an
application.
Data dictionary lists all data elements but does not say anything about relationships
between data elements.
Relationships are needed to logically group data elements into related sets or tables.
Such an organization
o Reduces data duplication
o Simplifies adding, deleting and updating data
o Simplifies retrieval of desired data
Logical databases give conceptual model..
Logical databases need to be stored in physical media such as a hard disk for use by
applications.
A system is needed to map the logical database to a physical medium, which is
transparent to an application program..
Database management systems achieve this purpose.
V. Rajaraman/IISc. Bangalore
Indian Institute of Science Bangalore
//V1/July 04/1
What is Data Dictionary
• Data dictionary is a catalogue of all data used in an application, In
other words it is data about data which is called metadata
• Data dictionary gives a single point reference of data repository of
an organization
• It is thus an important documentation which would be useful to
maintain a system
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How is Data
Dictionary Developed?
• Starting point is DFD
Example :
Consider the Receiving office process described in Module 3.
DFD is reproduced below.
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How is Data
Dictionary Developed? (Contd.)
Vendor
Delivery
note
Receiving
Process
Items
Received
note
Inspection
Office
Purchase
Office
Orders
Discrepancy
note
We will recall the word statement from requirement
specification now.
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Word Statement
of Requirements
• Vendor sends items with a delivery note while
fulfilling an order (along with the physical items) to a
receiving office.
• Receiving office compares a delivery note against
order placed.If there is a discrepancy a discrepancy
note is sent to purchase office.
• Actual items received note is sent to the inspection
office along with items received.
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Data Elements in Data Flow
From word statement we derive data elements in each data flow.
1. Delivery note
• Order no,Vendor name, Vendor address, item name, delivery
date, quantity supplied, units
• Item name and Vendor name may not be unique to ensure
uniqueness we assign unique codes for them.
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Data Elements
in Data Flow (Contd.)
Name is however still kept to aid people.
Thus delivery note is:
Delivery note = Order no + Vendor code +
Vendor name + Vendor address + item code +
item name + delivery date + quantity supplied
+ units.
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Data Elements in Data Flow
Discrepancy note : Order no + Vendor code + Vendor name +
Vendor address + item code + item name + delivery date + quantity
supplied + units + excess/deficiency + no of days late/early.
Items received note = Delivery note
Data in data store
Order records = order no + vendor code + vendor name + vendor
address + item code + item name + order date + qty ordered + units
+ delivery period.
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Data Dictionary Format
Data dictionary gives in detail the characteristics of a data element.
Typical characteristics are:
Data name : Should be descriptive and self explanatory.This
will help in documentation and maintenance
Data description : What it represents
Origin : Where the data originates
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Data Dictionary
Format (Contd.)
e.g. input from forms, comes from receiving office, keyed in by
user etc.
Destination : Where data will flow and will be used (if any)
Data Type : numeric, alphanumeric,letters(or text),binary(0 or 1;
True or False), Integer, Decimal fixed point, real (floating point),
currency unit, date
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Typical Characteristics
of Data Elements(contd)
Length : no of columns needed
Limits on value : (if relevant)
e.g. upper and lower bounds of value (age>0,<100)
Remarks : (if any)
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Example of
Data Dictionary Entry
Name : Order number
Description : Used to identify order given to vendor
Origin : Part of delivery note from vendor
Destination : Receiving process
Data type : Numeric Integer
Length : 8 digits
Limits on value : >000,<=99999999
Actual value not relevant.Used only as unique identifier
Remarks: It is a key field.
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Example of Data
Dictionary Entry (Contd)
Name : Delivery date
Description : Date item is to be delivered
Origin : Part of delivery note from vendor.Is also in orders data
store which is input to receiving process
Destination : Receiving process
Data type : Numeric Integer
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Example of Data
Dictionary Entry (Contd)
Length : 8 digits
Limits on value : Date field in the form DDMMYYYY.
Should satisfy constraints of a date in calendar
Remarks: Blank fields not allowed.
e.g. 05082004 is ok but not 582004
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Data Dictionary Uses
• Data dictionary can be enormous in size.Requires careful
development. However,it is centralized reference document.
• Invaluable resource to design
• Input forms and screens
• Data checking programs
• Process specification
• Database
• Very useful in understanding and maintaining system
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Data Input Methods
• On-line - User directly Enters data using
screen prompts
• Off-line -Forms filled by users- for
example-candidates for admission to a college
fill forms
• Data from forms keyed in by a data entry
operator
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Error Sources
• Errors in on-line data entry due to poor screen design. System
should inform the user immediately when wrong data is input
• Errors in off-line data entry due to bad form design and
human errors by users and data entry operator
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Error Sources
System should prevent user making mistakes by
• Good form design by leaving enough space
for writing legibly
• Clear instructions to fill form
System should prevent data entry operator making mistakes by
• Good form design
• Reducing key strokes
• Immediate error feedback
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Off Line
Data Entry - Problems
• Forms batched
• Desirable for the machine to give message when input is
wrong. Not always possible
• Error found after elapse of time
• Need good controls to automatically detect and if possible
correct errors
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Batch Data Entry
Data entered
in forms
Keyboard
Data entry
Input
batch
Input file
Error
batch
Error
report
Output report
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Data validation
program
Data processing
program
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Update
program
Data
store
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Batch Data Entry
Name
Address
Bad design : Tendency will be to fill
name on top line. Not enough space for
letters of address
Tick as applicable
Individual
Hindu undivided family
Parent/Guardian of minor
V.Rajaraman
Bad design : Choices are not codified.
Data entry operator will be confused.
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Batch Data Entry
Enter date
Enter date
Day Month Year
(Bad design)
(Good design)
Enter time
Hr Min Sec
Enter time
(Good design)
(Bad design)
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Batch Data Entry
Enter name and address using capital letters
Use one box for each alphabet
Tick any of the following
Shri
Smt
1
Kum
2
3
Name
Only address (do not
Repeat name)
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Pin
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Batch Data Entry (Contd.)
I am applying as:
Tick one of the boxes below
Individual
Hindu undivided
family
Parent or guardian
Of minor
Clear instructions . Enough space for entry manually.
Data entry operator can be simple instructions for data entry
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Computer Readable Forms
• As manual data input from forms are slow and expensive
attempts have been made to automate form reading using
scanners
• Needs hand writing recognition and correct form alignment –
Not very successful
• However if forms require just darkening some pre-defined
areas they can be machine read and interpreted.
• Example – Multiple choice questions in exams where specific
boxes are darkened based on the choice.
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Interactive Data Input
• Advent of PC’s and client/server model in computer
networks, interactive data input is now widely used
• Advantages are instant response when data is input so
that errors are immediately corrected.
• Flexibility in screen design which minimizes manual
effort
• Use of mouse and icons simplifies pre-determined
choices of data
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Interactive Data Input
Three main models of interactive data input :
• Menus
• Templates
• Commands
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Models of Data Input
Menus:
User Presented Several Alternatives And Asked To Type
His/Her Choice
Example
Select Alternative
Type 1 For entering new student record
Type 2 For deleting student record
Type 3 For changing student record
Your choice
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Models of Data Input
Template:
Template analogous to form
• Has features to reject incorrect data input using built-in program
• User friendly visual presentation
Example:
Roll no
Name
FIRST NAME/INTIALS
V.Rajaraman
LAST NAME
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Models of Data Input (Contd.)
Dept code
CE
CS
ME EE IT
Year
Hostel code
A
CODES
B
C
D
Pre-programmed to reject incorrect Roll no, Dept code,
Year, Hostel code
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Models of Data Input
Interactive commands guides user through alternatives
Example
Computer : Did you request deletion of record ?
Type Y or N
User
:Y
Computer : Give student roll no
User
: 56743
Computer : Is name of the student A.K.Jain?
Type Y or N
User
:Y
Computer : Is he 1st year student
Type Y or N
User
:Y
Computer : Shall I delete name?
User
:Y
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Models of Data Input
• Normally all three models will occur together in application .
In other words Menu, Forms and Commands are not mutually
exclusive.
• Graphical user interface design very rich area-languages such as
Visual Basic simplifies design of user interface.
• We have given only a flavor of the topic.
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Why do we need Codes?
Need for Coding:
• Unique Identifier
- Example Roll no instead of name
• Cross Referencing Between Applications
- Unique Roll no may be used in examination
records,accounts, health centre
• Efficient Storage And Retrieval
- Codes concise- a long name will have a shorter
roll no
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What are the Requirements
of a Good Code?
• Concise - Smallest length to reduce storage and data input effort
• Expandable - Add new members easily
• Meaningful- Code must convey some information about
item being coded
• Comprehensive - Include all relevant characteristics of item
being coded
• Precise - Unique, unambiguous code
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What methods
do we use to Code
1) Serial No: Assign serial number to each item
2) Block Codes: Blocks of serial numbers assigned to different
categories.
3) Group Classification Code- Groups of digits/characters
assigned for different characteristics
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What methods do
we use to Code (Contd.)
Roll no
87
1
05
2
Year
admitted
Term
admitted
Dept
Status
UG/PG
Serial No
in Dept
1
CS
UG
465
(use
meaningful
characters) 87
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465
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What Methods do
we use to Code (Contd…)
4) Significant Codes - Some Or All Parts Given Values
Roll no
BA
1
95
Banian Male Chest
Size
(cms)
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C
Cotton
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B
R
Style
Color
(Round (blue)
neck)
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Characterstics of Codes
Characteristics
Codes
Concise
Expandable
Meaningful Comprehensive
Precise
SERIAL NO
Yes
Yes
No
No
Yes
BLOCK CODES
Moderate
Yes
No
No
Yes
GROUP
CLASSIFICATION CODE
No
Yes
Yes
Yes
Yes
SIGNIFICANT
CODE
No
Yes
Yes
Yes
Yes
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Error Detection Code
• Incorrect data entry can lead to chaos
• Mistakes occur as volume of data processed is large
• Need to detect and if possible correct errors in data entry
• Error detected by introducing controlled redundancy in codes
• Error control digits added based on statistics of types of
errors normally committed during data entry
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Modulus 11
Check Digit System
• Error detection digit added at the end of a numeric code
• Code designed in such a way as to detect all single transcription
and single transposition errors which is 95% of all errors
Single transcription errorÆ 49687Æ48687
Single transposition errorÆ 45687Æ48657
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Modulus 11
Check Digit System
• Given code 49687 modulus check digit obtained as
follows: Multiply each digit by
Weights of 2,3,4 etc starting with least significant digit
7*2+8*3+6*4+9*5+4*6=131
131/11=11,remainder 10; or 131 mod (11) =10;
(11-10)=1 append it to the code
• The code with check digit=496871
• If remainder is 1 then append(11-1)=10 code as X
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Error Detection
496871
Correct code
486871
Code as entered
Error detection - 1*1 + 7*2 + 8*3 + 6*4 + 8*5 + 4*6
= 127/11 Remainder != 0 => Error
496871
Error detection -
416879
9*1 + 7*2 + 8*3 + 6*4 + 1*5 + 4*6
= 100/11 Remainder != 0 => Error
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Why does Modulus
11 Check Digit Work
•
Given dn, dn-1,……..d1 where d1 is the check digit
n
(∑Widi ) mod N=0 by design
i=1
What should be the values of N & Wis
Single transcription error: dk become t
n
n
(∑Widi ) = (∑Widi ) + t Wk - Wk dk
i=1
i=1
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Why does Modulus
11 Check Digit Work (Contd.)
As (∑Widi ) mod N=0 (t- dk ) Wk mod N = 0
(t- dk ) Wk = p.N where p is any integer
Conditions
1. integer not a prime => N a prime
2. Smallest 0<Wk<N
3. As [t-dk] < 10 and Wk < N, N>10
4. Product of prime > 10 =11 => N=11
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Why does Modulus
11 Check Digit Work
Given dn,dn-1,……..d1 where d1 is the check digit
n
(∑Widi ) mod N=0 by design
i=1
What should be the values of N & Wis
Single transcription error: dk become t
n
n
(∑Widi ) = (∑Widi ) + t Wk - Wk dk
i=1
i=1
As (∑Widi ) mod N=0 (t - dk ) Wk mod N = 0
•
(t-dk ) Wk = p. N where p is any integer
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Why does Modulus
11 Check Digit Work
Single transposition error
Let dk and dm get interchanged
n
[ ∑ Wi,di + (dkWm + dmWk - dkWk - dmWm )] mod N = 0
i=1
Or (dk-dm)(Wm-Wk) = p.N
1. (Wm - Wk) = 0 => Weights distinct
2. (dk- dm) <10 If N> 10 equation satisfied
3. If N prime product cannot be prime
therefore N =11 satisfies conditions
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Other Checking Systems
• Use modulo n check with n prime > largest code
character value
• For hexadecimal codes symbols = 16, n =17
• For alphanumeric codes
26 letters
10 digits
36 symbols
• Therefore n=37.
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Validating Input Data
• When large volume of data is input special precautions
needed to validate data
• Validation checks :
• Sequence Numbering - Detects Missing Record
• Batch Control - Use Batch Totals
• Data Entry And Verification-dual Input
• Record Totals-add Individual Values For checking
• Modulus 11 Check Digit
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Checks on Individual Fields
• Radix errors - For example seconds field cannot exceed
60,month field cannot exceed 12
• Range check - Fields should be within specified range
• Reasonableness check - Telephone bill cannot be more
than 10 times average bill of last few months
• Inconsistent data - For example : 31-04-99
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Checks on
Individual Fields (Contd.)
• Incorrect data- Batch total checks this
• Missing data - Batch control data checks this
• Inter field relationship check • For example - Student of 8lh class cannot have age > 25
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Prof. V.Rajaraman
System Analysis and Design
System Analysis and Design / Data Oriented Systems Design
Question Bank
Question Bank – 7
7.1 What is a data dictionary?
7.2 Why is a data dictionary necessary?
7.3 What are the main advantages of creating a data dictionary?
7.4 What data about a data element is stored in a data dictionary?
7.5 For the requirements statement given in PPT 7.1.3 (Vendor supplying items to a
company) develop the data dictionary entry for vendor code, vendor name and
vendor address.
7.6 What is the difference between on-line and off-line data entry?
7.7 Why are input data records divided into batches for off-line data entry?
7.8 What is the purpose of a data validation program?
7.9 What are the main principles used in designing forms for data entry?
7.10 A good and a bad design for entering date in a form is given in Section PPT 7.2.5
and 7.2.6. What are the reasons for saying that one of them is good and the other
bad?
7.11 Design a form to be used by a salesman to report to the office about the sales
executed by him at different customer locations.
7.12 What is the main difference between menus, templates and command modes of
interactive data entry? When is each of these modes appropriate?
7.13 Design a dialogue hierarchy for entering data on customers (of a manufacturer).
7.14 Design a dialogue hierarchy and the screens for a system used to reserve seats in
long distance buses.
7.15 Why are data fields coded in an information system?
7.16 Can the name of a person be used as a code, for say, his bank account? If not,
why?
V. Rajaraman/IISc. Bangalore
Indian Institute of Science Bangalore
M7/V1/July 04/1
Prof. V.Rajaraman
System Analysis and Design
System Analysis and Design / Data Oriented Systems Design
Question Bank
7.17 What are the requirements of a good coding scheme?
7.18 Is a concise code comprehensive? If not, why?
7.19 Is a meaningful code necessarily comprehensive?
7.20 Is a comprehensive code necessarily meaningful?
7.21 Is a precise code necessarily concise?
7.22 What is the advantage of a serial number code? Why is it not normally used?
7.23 What is the main advantage of block codes?
7.24 Design a group classification code to code (i) motor vehicles,, (ii) music cassettes,
and (iii) books
7.25 Is a group classification code meaningful?
7.26 Give an example of a significant code. Are significant codes expandable?
7.27 Add a Modulus-11 check digit to the codes (i) 48467, (ii) 96432, and (iii)
87646257.
7.28 Modulus-37 check is suitable for alphanumeric codes. Add a modulus-37
character to the codes (i) 4AB9W, (ii) XBY483, and (iii) CAZ4642.
7.29 The following code was entered by an operator:449632. The last digit is a
modulus-11 check digit. Is this code correct?
7.30 If a code uses hexadecimal digits, what should be N if the modulus-N check digit
system is to be used with such codes? What are the allowable weights if single
transcription and transposition errors are to be detected?
7.31 If modulus-11 check digit system is to generate detection of multiple identical digit
transcription error (i.e., a code such as 45565 is wrongly entered as 48868), what
should be the constraints on the weights?
V. Rajaraman/IISc. Bangalore
Indian Institute of Science Bangalore
M7/V1/July 04/2
Prof. V.Rajaraman
System Analysis and Design
System Analysis and Design / Data Oriented Systems Design
Question Bank
7.32 A see-saw error is one in which one digit of the code is increased by x and another
decreased by x. For example, 486732 becoming 456762. When can modulus N
check detect such errors?
7.33 Why is it useful to assign sequence numbers for data records? What are the types
of errors detected by sequence numbering?
7.34 What is the purpose of batch control record? What is the type of information
contained in a batch control record?
A set of data records for student examination results has the following format:
Roll no. Name Marks (out of 100)
Paper 1
Paper 2
Paper 3
Paper 4
Design for these records a batch control record and a record control field and any other
appropriate checks for the fields.
7.35 Give some example of fields for which a radix error check is appropriate.
7.36 What is the difference between range check and a radix check?
7.37 What are the appropriate range checks for the age of individuals in an employee
file, a high school student file, and height of students in a student file.
7.38 Give some examples of fields where reasonableness check would be applicable.
7.39 Give some examples of inter-field relationship checks.
7.40 What is the main difference between menus, templates and command modes of
interactive data entry? When is each of these modes appropriate?
7.41 Design a dialogue hierarchy for entering data on customers (of a manufacturer).
7.42 Design a dialogue hierarchy and the screens for a system used to reserve seats in
long distance buses.
V. Rajaraman/IISc. Bangalore
Indian Institute of Science Bangalore
M7/V1/July 04/3
Prof. V.Rajaraman
System Analysis and Design
Summary Module 7
1. Data dictionary is a catalogue of all data used in an application. Each entry in the
dictionary has the name of the data, its type, origin, destination, range of
values,length and where used.
2. It is useful as a documentation and assists in maintaining systems and also in
designing data input.
3. Data dictionary is developed using data flows in a DFD and contents of data stores
in DFD
4. Data may be input to a computer off-line or on-line. In on-line entry a user enters
data interactively via a video terminal connected to the computer. In off-line data
entry data filled in forms are entered by operators in a separate PC or a data entry
machine.
5. Off-line data entry is suitable if the number of records is very large.
6. In off-line data entry, batches of data are formed and entered. They are checked by a
validation program and the corrected records are stored in a file.
7. To reduce errors in input, it is essential to carefully design the forms used for
entering data.
8. For interactive data input, special screens are designed on video terminals for easy
data entry. Errors in data entry are instantly detected by a validation program during
data entry and can be immediately corrected.
9. Common methods of interactive data input is by use of menus, templates and
interactive commands for data entry.
10. A menu method is used to pick one out of many alternatives, a template method to
enter new data, and a command method to add and delete data.
Indian Institute of Science Bangalore
System Analysis and Design
Prof. V.Rajaraman
11. These methods are combined to provide a user the most appropriate technique for a
particular type of interactive data entry.
12. Important data elements are coded. Codes are necessary for unique identification,
easily cross-referencing and efficient storage and retrieval.
13. There are many methods for coding. An ideal code must be concise, expandable,
meaningful, comprehensive and precise. It is not possible to incorporate all these
ideal features in a code.
14. Codes are classified as: (i) Serial number codes, (ii) Block codes, (iii) Group
classification codes, and (iv) Significant codes. Group classification codes and
Significant codes are most meaningful, expandable, precise and comprehensive.
They are, however, not concise, Serial and Block number codes are more concise.
They are also precise and expandable but are not meaningful and comprehensive.
15. Any error made in entering important data fields such as account codes and
identification codes must be detected during data entry.
16. The most common errors made during data entry are: a single digit is incorrectly
entered or any two digits in the code are interchanged. These errors are called
respectively single transcription and transposition errors and account for 96% of all
data entry errors.
17. Given a code, the digits in it starting from the last digit are multiplied by weights 2,
3, 4, etc., and the products are added. The sum is divided by 11. The remainder is
subtracted from 11. This number (which is called a check digit) is appended as the
last digit of the code. The code constructed in this way is called a midulus-11 check
digit code.
Indian Institute of Science Bangalore
System Analysis and Design
Prof. V.Rajaraman
18. After data entry the digits in the code starting from the last digit are multiplied by
weights 1, 2, 3, 4, etc., and the products are added. The sum is divided by 11. If the
remainder is not zero then there is an error in the code.
19. Modulus-11 check digit code guarantees detection of all single transcription and
transposition errors. It also detects 95% of all other errors.
20. It is essential to design good data validation programs to prevent data entry errors
from corrupting files of input data. Validation programs need information for
detecting errors. This information is provided by controls exercised during data
preparation.
21. Important control mechanisms are; giving unique sequence numbers to each data
record, providing a batch control record containing a count of number of records and
a total of one of the fields..
22. The same data is entered by two different persons and compared to reduce
transcription errors.
23. Besides this, individual data fields are checked using information on their range of
allowed values, range of reasonable values, and relationships between different
fields. Batch control provides information to detect incorrect values entered, missing
records, and data in the wrong sequence.
24. With the advent of Personal Computers, remote terminals connected to a computer
and local computer networks, considerable amount of data is entered in files
interactively.
Indian Institute of Science Bangalore
Prof. V.Rajaraman
System Analysis and Design
System Analysis and Design/Data Oriented Systems Design
Worked Out Problems
Worked Examples
7.1 What is the purpose of data validation program?
To detect errors which may have been made by a data entry operator in entering data
from forms into a computer’s secondary memory. The detected errors are then
corrected to ensure that data file has no errors.
7.2 What are the main principles used in designing forms for data entry?
(i) Reduce human efforts in filling forms
(ii) Minimize possibility of errors in entering data from forms into a computer’s
secondary memory
(iii)Minimize effort in entering data from forms into a computer’s secondary
memory.
7.3 Design a form to be used by a salesman to report to the office about the sales
executed by him at different customer locations
See Table below
A Salesperson Form
Sales Person
Your name :
M . R A M A M U R T H Y
Your code :
M R 4
Your budget code: 1 2
Sales details
D D M M Y Y
Date:
Item Code
Description
Qty. Sold
Price
K 2 4 8
Toilet soap
256
3.50
J 4 6 8
Detergent cake
468
2.25
P 7 6 4
Liquid soap bottles
28
8.45
752
14.20
Enter Totals
V. Rajaraman/IISc. Bangalore
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M7/V1/July 04/1
Prof. V.Rajaraman
System Analysis and Design
System Analysis and Design/Data Oriented Systems Design
Worked Out Problems
Customer details
Customer name:
Customer code:
Customer address:
PIN
Mode of payment (Tick code)
1 CASH
2 CHEQUE
3 BILL
7.4 Is concise code comprehensive? If not, why?
No. In a concise code the aim is to keep the length of the code small whereas in a
comprehensive code it is to include as much information as possible about the entity
being coded.
7.5 Is meaningful code necessarily comprehensive?
No. Meaningful code aids in recognizing the entity being coded whereas a
comprehensive code tries to include as much information as possible about the
entity being coded. For example BICYCLE 24 indicates a 24 inch height cycle. It is
meaningful. A code such as
BC 24 G R HERO 2684
Describes 24-inch bicycle, which is for gents, red in color, manufactured by Hero
with serial number 2684.
7.6 What is the advantage of serial number code? Why is it not normally used?
It is concise, expandable and precise. It is not meaningful or comprehensive and
thus not often used.
7.7 Design a group classification code to code (i) motor vehicles, (ii) music cassettes,
and (iii) books.
(i) Motor vehicles
Types of
vehicle
2 alphabets
Year of
manufacture
4 digits
Engine
CC
4 digits
Brand
Serial no.
3 alphabets
7 digits
Mnemonic codes
Vehicle types
Two wheeler
Three wheeler
Private car
Taxi
Bus
V. Rajaraman/IISc. Bangalore
Indian Institute of Science Bangalore
code
TW
RW
PC
TA
BU
Manufacturer
Bajaj
Telco
Leyland
Maruti
Ambassador
Vespa
Code
BAJ
TEL
LEL
MAR
AMB
VSP
M7/V1/July 04/2
Prof. V.Rajaraman
System Analysis and Design
System Analysis and Design/Data Oriented Systems Design
Worked Out Problems
Fiat
Honda
FAT
HDA
Sample code: PC 19 88 800 MAR 0056789
(ii) Music cassettes
Types of music
Nature of music Type
Publisher code Serial no.
2 alphabets
2 alphabets
3 digits
1 digit
4 digits
Mnemonic codes
Music type
Code
Nature of music
Code
Classical North
Classical South
Classical West
Film North
Film South
Film West
Pop North
Pop South
Pop West
CN
CS
CW
FN
FS
FW
PN
PS
PW
Instrumental
Vocal
Orchestra
Chorus
IN
VO
OR
CH
Type
Mono
Stereo
Code
1
2
Publisher code: 3 digits, Serial no.: 4 digits.
Example: FNIN14506784
(iii) Books
ISBN code is a good example.
Area
U.S.
U.K.
Germany,
U.S.S.R. etc.
Example: 0
Publisher
code
Book no.
8 digits (Total)
Check digit
Publishers publishing a small number of books have a long
publisher code and smaller no. of digits for book no.
| 87692
| 617
| 0
7.8 Give an example of significant code. Are significant codes expandable?
Code for a shirt
SH
40
95
58
Shirt
Collar size
(Cm)
Chest size
(Cm)
Sleeve size
(Cm)
Yes.
7.9 Add a modulus-11 check digit to the codes (i) 48467 (ii) 96432 and (iii) 87646257.
Check digits are respectively
(i) 9 (ii) 8 (iii) 3.
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Indian Institute of Science Bangalore
M7/V1/July 04/3
Prof. V.Rajaraman
System Analysis and Design
System Analysis and Design/Data Oriented Systems Design
Worked Out Problems
7.10 Modulus–37 check is suitable for alphanumeric codes. Add a modulus-37
character to the codes (i) 4AB9W (ii) XBY483 and (iii) CAZ4642.
(i) 2 (ii) N (iii) N.
7.11 If modulus-11 check digit system is to generate detection of multiple identical
digit transcription error (i.e., a code such as 45565 is wrongly entered as
48868), what should be constraints on the weights?
A digit t becomes x for weights wq, wr, ws.
Let wi be the weights.
n
∑ widi = p.N if no error
i=1
n
n
∑ widi = ∑ widi + (wq+ wr+ ws)t =p.N
i=1
i=1
i == q,r,s
The condition for detecting error is
(wq + wr + ws)(x – t) == p.N
Therefore,
(wq + wr + ws) == p.N
Sum of any subset of weights should not be equal to 11 or a multiple of 11.
Possible only for codes less than 4 digits long, including check digit.
7.12 A see-saw error is one in which one digit of the code is increased by x and
another decreased by x. For example, 486732 becoming 456762. When can
modulus-N check detect such errors?
Let the kth digit become (dk + t) and qth digit (dq – t)
Weighted sum =
∑n
i =1
widi + wkt – wqt with these errors condition is
∑n
widi + t(wk – wq) == p.N
Satisfied if (i) wk == wq
(ii) N is prime
(iii) |wk – wq| < N
These are satisfied if wk = wq, wk, wq > 0 and wk, wq < N.
Therefore all weights are distinct
i =1
7.13 Why is it useful to assign sequence numbers for data records? What are the types
of errors detected by sequence numbering?
Can trace missing records using sequence numbers. Records out of sequence can be
detected. Excess records (with duplicate sequence numbers) can be detected.
7.14 A set of data records for student examination results has the following format:
Roll No. Name
V. Rajaraman/IISc. Bangalore
Indian Institute of Science Bangalore
Marks (out of 100)
M7/V1/July 04/4
Prof. V.Rajaraman
System Analysis and Design
System Analysis and Design/Data Oriented Systems Design
Paper 1
Paper 2
Worked Out Problems
Paper 3
Paper 4
Design for these records a batch control record and a record control field and
other appropriate checks for the fields
Batch control record
(i) No. of records in batch
(ii) Sum of marks in papers 1 to 4
(iii) No. of records with marks in papers 1 to 4 >=60
(iv) No. of records with marks in papers 1 to 4 < 40
Record check (i) Sum of marks in papers 1 to 4, (ii) No. of papers in record with
marks >= 60
Other checks for the fields
(i) Modulus-11 check for Roll no.
(ii) Each marks field <= 100, >= 0
(iii) Sum field <= 400
(iv) Flag record with marks in any paper >= 80 and another paper <= 30.
7.15 What is the difference between range check and radix check?
Range gives maximum allowable value for a field as determined by the analyst. For
example in one paper if maximum marks is 50, range check will use 50 and if it is
100 in another it will use 100 as range. Radix is however an invariant. No. of
hours/day are always 24 and is universally known.
7.16 Give some examples of fields where reasonableness check would be applicable.
If normal electricity consumption of a consumer is 250 kWh/month, a value of 1500
kWh in a month will be considered unreasonable. Other examples are:
(i) Deductions in a paybill
(ii) Price/unit of some items
(iii)Qty. ordered in comparison to normal averages.
7.17 Give some examples of inter-field relationship checks
Employee status vs. salary
Age vs. marital status (Age <= 12 cannot normally be married)
Age vs. Education
7.18 Design a dialogue hierarchy for entering data on customers (of a manufacturer).
Select Menu alternative
1
2
3
New customer
Delete customer
Change customer
details
Enter details
Enter details
Details to be changed
Verify
OK
V. Rajaraman/IISc. Bangalore
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No
New
name
New
address
Status
change
M7/V1/July 04/5
Prof. V.Rajaraman
System Analysis and Design
System Analysis and Design/Data Oriented Systems Design
Delete
Worked Out Problems
Manual
0
1
2
3
Individual
Retailer
Distributor
Wholesale
Design a dialogue hierarchy and the screens for a system used to reserve
seats in long distance buses.
7.19
Select Menu alternative
1
2
3
Reservation
Cancellation
Change of date
Queries to customer Queries to customer
1. Destination
1. Destination
2. Date
2. Date
3. Time
3. Time
4. No. of seats
4. No. of seats
5. Display position
5. Display refund
of seats (status)
6. Enter selection
7. Display ticket
Queries to customer
1. Destination
2. Date
3. Time
4. New date
5. New time
6. No. of seats
7. Display position
8. Enter selection
9. Display excess charge
Screen 1
•
•
•
•
•
Reservation 1
Cancellation 2
Change of date
Screen 2 reservation commands
What is your destination ?
• Queries on terminal
Mercara
User responses
Date of journey?
260589
Time of bus
0830
How many seats?
• Adults 2 • child 1
Screen display
Front
(Seats in bus)
1
2
Entrance
4
5
6
7
8
9
10
11
12
13
14
V. Rajaraman/IISc. Bangalore
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3
3
already
booked
M7/V1/July 04/6
Prof. V.Rajaraman
System Analysis and Design
System Analysis and Design/Data Oriented Systems Design
Worked Out Problems
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
•
Which seats do you want ?
19 20 21
• Ticket display
DESTINATION
DATE
TIME
SEAT Nos.
FARE
MERCARA
260589
0830
19
Rs. 140
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20
21
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Prof. V.Rajaraman
System Analysis and Design
System Analysis and Design/Data Oriented Systems Design
7.1
A data dictionary has consolidated list of data contained in
(i) dataflows
(ii) data stores
(iii) data outputs
7.2
Multiple Choice Questions
(iv) processes
a. (i) and (iii)
b. (i) and (ii)
c. (ii) and (iv)
d. (i) and (iv)
A data dictionary is useful as
(i) it is a documentation aid
(ii) it assists in designing input forms
(iii) it contains al data in an application including temporary data used in
processes
(iv) it is a good idea in system design
7.3
7.4
7.5
7.6
a. (i) and (ii)
b. (i) and (iv)
c. (i),(ii) and (iii)
d. (i) and (iv)
By metadata we mean
a. very large data
b. data about data
c. data dictionary
d. meaningful data
A data dictionary is usually developed
a. At requirements specification phase
b. During feasibility analysis
c. When DFD is developed
d. When a datadase is designed
A data dictionary has information about
a. every data element in a data flow
b. only key data element in a data flow
c. only important data elements in a data flow
d. only numeric data elements in a data flow
A data element in a data dictionary may have
a. only integer value
b. no value
c. only real value
d. only decimal value
V. Rajaraman/IISc. Bangalore
Indian Institute of Science Bangalore
M7/V1/July 04/1
Prof. V.Rajaraman
System Analysis and Design
System Analysis and Design/Data Oriented Systems Design
7.7
Multiple Choice Questions
A data element in a data flow
(i) may be an integer number
(ii) may be a real number
(iii)may be binary
(iv)may be imaginary
a. (i),(ii),(iv)
b. (iii),(iv),(ii)
c. (i),(ii),(iii)
d. (i) and (ii)
7.8 It is necessary to carefully design data input to a computer based system
because
a. it is good to be careful
b. the volume of data handled is large
c. the volume of data handled is small
d. data entry operators are not good
7.9
Errors occur more often when
a. data is entered by users
b. data is entered by operators
c. when data is handwritten by users and entered by an operator
d. the key board design is bad
7.10 Good
system
design
prevents
data
entry
errors
by
(i) Designing good forms with plenty of space to write in
block capitals
(ii)By giving clear instructions to a user on how to fill a form
(iii)Reducing keystrokes of an operator
(iv)Designing good keyboard
a. i, ii, iii
b. i, ii, iv
c. i, ii
d. iii and iv
7.11 In on-line data entry it is possible to
a. Give immediate feedback if incorrect data is entered
b. Eliminate all errors
c. Save data entry operators time
d. Eliminate forms
7.12 The main problems encountered in off-line data
(i)Data are entered by operators
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entry
are:
M7/V1/July 04/2
Prof. V.Rajaraman
System Analysis and Design
System Analysis and Design/Data Oriented Systems Design
Multiple Choice Questions
(ii)Data entered by hand in forms batched and forms may be missed
or misread
(iii) Errors are detected after a lapse of time
(iv)Data are entered by users
7.13
7.14
7.15
7.16
7.17
7.18
7.19
7.20
a. i and ii
b. i and iii
c. ii and iii
d. iii and iv
In interactive data input a menu is used to
a. enter new data
b. add/delete data
c. select one out of many alternatives often by a mouse click
d. detect errors in data input
In interactive data input a template is normally used to
a. enter new data
b. add/delete data
c. select one out of many alternatives often by a mouse click
d. detect errors in data input
In interactive data input terminal commands are normally used to
a. enter new data
b. add/delete data
c. select one out of many alternatives often by a mouse click
d. detect errors in data input
Data inputs which required coding are
a. fields which specify prices
b. key fields
c. name fields such as product name
d. fields which are of variable length
Key fields are normally coded
a. i and ii
b. i and iv
c. ii and iii
d. i and iii
A code is useful to represent a key field because
a. it is a concise representation of the field
b. it is usually done by all
c. it is generally a good idea
d. it is needed in database design
By the term “concise code” we understand that the code
a. conveys information on item being coded
b. is of small length
c. can add new item easily
d. includes all relevant characteristics of item being coded
By the term “expandable code” we understand that the code
a. conveys information on item being coded
b. is of small length
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Prof. V.Rajaraman
System Analysis and Design
System Analysis and Design/Data Oriented Systems Design
7.21
7.22
7.23
7.24
Multiple Choice Questions
c. can add new item easily
d. includes all relevant characteristics of item being coded
By the term “meaningful code” we understand that the code
a. conveys information on item being coded
b. is of small length
c. can add new item easily
d. includes all relevant characteristics of item being code
By the term “comprehensive code“ we understand that the code
a. conveys information on item being coded
b. is of small length
c. can add new item easily
d. includes all relevant characteristics of item being coded
A concise code is necessarily
a. Precise
b. Meaningful
c. Comprehensive
d. Difficult
Serial numbers used as codes are
(i) concise
(ii ) meaningful
(iii) expandable
(iv) comprehensive
a. i and ii
b. ii and iii
c. ii and iv
d. i and iii
7.25 Block codes are
(i)concise
(ii )meaningful
(iii)expandable
(iv)comprehensive
a. i and ii
b. ii and iii
c. iii and iv
d. i and iii
7.26 Group classification codes are
(i)concise
(ii)meaningful
(iii) expandable
V. Rajaraman/IISc. Bangalore
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M7/V1/July 04/4
Prof. V.Rajaraman
System Analysis and Design
System Analysis and Design/Data Oriented Systems Design
Multiple Choice Questions
(iv)comprehensive
a. i and ii
b. i, ii and iii
c. ii, iii and iv
d. i, ii and iv
7.27 Significant codes are
(i)concise
(ii)meaningful
(iii )expandable
(iv)comprehensive
7.28
7.29
7.30
7.31
7.32
a. i and ii
b. i, ii and iii
c. ii, iii and iv
d. i, ii and iv
In significant codes some or all parts of the code
a. are meaningful
b. are usable
c. are significant
d. represent values
Errors in codes are detected by
a. proper design of code
b. introducing redundant digits/characters designed to detect errors
c. making the code concise
d. making the code precise
Design of error detecting codes requires good
a. knowledge of mathematics
b. statistical mechanics
c. statistics of errors normally committed during data entry
d. Boolean algebra
A modulus-11 check digit is used to detect error in
a. alphanumeric codes
b. numeric codes
c. hexadecimal codes
d. serial number code
A modulus-11 check digit will detect
(i)single transcription errors
(ii)single transposition errors
(iii)multiple digit transcription errors
(iv)and correct a single error
a.
b.
c.
d.
i and iii
i and iv
i and ii
iii and iv
V. Rajaraman/IISc. Bangalore
Indian Institute of Science Bangalore
M7/V1/July 04/5
Prof. V.Rajaraman
System Analysis and Design
System Analysis and Design/Data Oriented Systems Design
Multiple Choice Questions
7.33 A modulus-17 check will detect single transcription errors in
a. alphanumeric codes
b. hexadecimal codes
c. decimal numerical codes
d. serial number codes
7.34 For modulus-11 check digit to detect a single transposition errors
a. weights should all be distinct
b. weights may all be equal and > 0
c. weights should be less than 8
d. weights should all be > 0 and distinct
7.35 For modulus-11 check digit to detect a single transcription errors
a. weights should all be distinct
b. weights may all be equal and > 0
c. weights should be less than 8
d. weights should all be > 0 and distinct
7.36 Modulus-11 check digit for the code 45672 is
a. 0
b. 1
c. 2
d. 3
7.37 Modulus-11 check digit for the code 85672 is
a. 0
b. 1
c. X
d. 3
7.38 For modulus-11 check digit to detect single transposition or single
transcription error the number of digits in the codes should not exceed
a. 9
b. 10
c. 11
d. 99
7.39 Modulus-17 check character for the hexadecimal code AB4567 is
a. F
b. D
c. 1
d. 0
7.40 Sequence numbering of records is used to
(i)Identify each record uniquely
(ii)Track a missing record in a batch of records
(iii)Count number of records
(iv) Sort the records
a.
b.
c.
d.
i, ii
i, ii, iii
i, ii, iii, iv
i and iv
V. Rajaraman/IISc. Bangalore
Indian Institute of Science Bangalore
M7/V1/July 04/6
Prof. V.Rajaraman
System Analysis and Design
System Analysis and Design/Data Oriented Systems Design
Multiple Choice Questions
7.41 A batch control record uses
(i)Batch totals of selected fields
(ii)A simple count of number of records in a batch
(iii)Modulus-11 check digit of each key field
(iv)Totals of selected fields of record totalled for the batch
7.42
7.43
7.44
7.45
7.46
7.47
7.48
a. i and ii
b. i, ii, iv
c. i, ii, iii, iv
d. iii and iv
A record total uses
a. batch totals of selected fields
b. count of numbers of records
c. modulus-11 check digit sum of all fields
d. total of selected fields of a record
If a field is known to represent an angle of a triangle, radix used to check
should be
a. 90
b. 60
c. 180
d. 360
If a field is known to represent days of a month, radix used to check should
a. 30
b. 31
c. 28
d. 29
Radix check for a field representing year is
a. Possible
b. not possible
c. not relevant
d. may be tried
An appropriate range check for marks in an examination paper whose
maximum marks 100 is
a. 100
b. 0 to 100
c. – 99 to +99
d. 99
An appropriate range check for month field in a date is
a. 12
b. –12 to 12
c. 1 to 12
d. 0 to 12
An appropriate range check of age of a tenth standard student in a high
school
a. 5 to 15
b. 10 to 25
V. Rajaraman/IISc. Bangalore
Indian Institute of Science Bangalore
M7/V1/July 04/7
Prof. V.Rajaraman
System Analysis and Design
System Analysis and Design/Data Oriented Systems Design
Multiple Choice Questions
c. 8 to 20
d. 3 to 18
7.49 Reasonableness checks for monthly mess bill of a student if daily rate is
Rs. 40 is
a. 1200
b. 12000
c. 120
d. 2400
7.50 Batch control totals will detect
(i)incorrect data entry of a field
(ii)missing record
(iii) data records out of order
( iv)inconsistent data
a.
i and ii
b.
i, ii and iii
c.
ii, iii and iv
d.
iii and iv
7.51 If records are out-of-order then error may be detected by
a. batch control totals
b. radix check
c. sequence number check
d. range check
7.52 In payroll record a reasonable inter-field relationship check is to relate
salary field with
a. age field
b. department field
c. designation field
d. increment field
V. Rajaraman/IISc. Bangalore
Indian Institute of Science Bangalore
M7/V1/July 04/8
System Analysis and Design
System Analysis and Design/Data Oriented Systems Design
Prof. V.Rajaraman
Multiple Choice Questions
Key to Objective Questions
7.1
b
7.2 c
7.3 b
7.4 c
7.5 a
7.6 b
7.7
c
7 .8 b
7.9 c
7.10 a
7.11 a
7.12
c
7.13
c
7.14
a
7.15 b
7.16
b
7.17
d
7.18
a
7.19
b
7.20
c
7.21
a
7.22 d
7.23
a
7.24
d
7.25 b
7.26 c
7.27
c
7.28 d
7.29 b
7.30
c
7.31 b
7.32 c
7.33
b
7.34 d
7.35 b
7.36 b
7.37 c
7.38 b
7.39
b
7.40 c
7.41 b
7.42
d
7.43 c
7.44 b
7.45 b
7.46 b
7.47 c 7.48 c
7.49 d
7.50 a
7.51
c
7.52
c
V. Rajaraman/IISc. Bangalore
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M7/V1/July 04/9
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System Analysis and Design
System Analysis and Design / Data Oriented Systems Design
Question Bank
Question Bank – 7
7.1 What is a data dictionary?
7.2 Why is a data dictionary necessary?
7.3 What are the main advantages of creating a data dictionary?
7.4 What data about a data element is stored in a data dictionary?
7.5 For the requirements statement given in PPT 7.1.3 (Vendor supplying items to a
company) develop the data dictionary entry for vendor code, vendor name and
vendor address.
7.6 What is the difference between on-line and off-line data entry?
7.7 Why are input data records divided into batches for off-line data entry?
7.8 What is the purpose of a data validation program?
7.9 What are the main principles used in designing forms for data entry?
7.10 A good and a bad design for entering date in a form is given in Section PPT 7.2.5
and 7.2.6. What are the reasons for saying that one of them is good and the other
bad?
7.11 Design a form to be used by a salesman to report to the office about the sales
executed by him at different customer locations.
7.12 What is the main difference between menus, templates and command modes of
interactive data entry? When is each of these modes appropriate?
7.13 Design a dialogue hierarchy for entering data on customers (of a manufacturer).
7.14 Design a dialogue hierarchy and the screens for a system used to reserve seats in
long distance buses.
7.15 Why are data fields coded in an information system?
7.16 Can the name of a person be used as a code, for say, his bank account? If not,
why?
V. Rajaraman/IISc. Bangalore
Indian Institute of Science Bangalore
M7/V1/July 04/1
Prof. V.Rajaraman
System Analysis and Design
System Analysis and Design / Data Oriented Systems Design
Question Bank
7.17 What are the requirements of a good coding scheme?
7.18 Is a concise code comprehensive? If not, why?
7.19 Is a meaningful code necessarily comprehensive?
7.20 Is a comprehensive code necessarily meaningful?
7.21 Is a precise code necessarily concise?
7.22 What is the advantage of a serial number code? Why is it not normally used?
7.23 What is the main advantage of block codes?
7.24 Design a group classification code to code (i) motor vehicles,, (ii) music cassettes,
and (iii) books
7.25 Is a group classification code meaningful?
7.26 Give an example of a significant code. Are significant codes expandable?
7.27 Add a Modulus-11 check digit to the codes (i) 48467, (ii) 96432, and (iii)
87646257.
7.28 Modulus-37 check is suitable for alphanumeric codes. Add a modulus-37
character to the codes (i) 4AB9W, (ii) XBY483, and (iii) CAZ4642.
7.29 The following code was entered by an operator:449632. The last digit is a
modulus-11 check digit. Is this code correct?
7.30 If a code uses hexadecimal digits, what should be N if the modulus-N check digit
system is to be used with such codes? What are the allowable weights if single
transcription and transposition errors are to be detected?
7.31 If modulus-11 check digit system is to generate detection of multiple identical digit
transcription error (i.e., a code such as 45565 is wrongly entered as 48868), what
should be the constraints on the weights?
V. Rajaraman/IISc. Bangalore
Indian Institute of Science Bangalore
M7/V1/July 04/2
Prof. V.Rajaraman
System Analysis and Design
System Analysis and Design / Data Oriented Systems Design
Question Bank
7.32 A see-saw error is one in which one digit of the code is increased by x and another
decreased by x. For example, 486732 becoming 456762. When can modulus N
check detect such errors?
7.33 Why is it useful to assign sequence numbers for data records? What are the types
of errors detected by sequence numbering?
7.34 What is the purpose of batch control record? What is the type of information
contained in a batch control record?
A set of data records for student examination results has the following format:
Roll no. Name Marks (out of 100)
Paper 1
Paper 2
Paper 3
Paper 4
Design for these records a batch control record and a record control field and any other
appropriate checks for the fields.
7.35 Give some example of fields for which a radix error check is appropriate.
7.36 What is the difference between range check and a radix check?
7.37 What are the appropriate range checks for the age of individuals in an employee
file, a high school student file, and height of students in a student file.
7.38 Give some examples of fields where reasonableness check would be applicable.
7.39 Give some examples of inter-field relationship checks.
7.40 What is the main difference between menus, templates and command modes of
interactive data entry? When is each of these modes appropriate?
7.41 Design a dialogue hierarchy for entering data on customers (of a manufacturer).
7.42 Design a dialogue hierarchy and the screens for a system used to reserve seats in
long distance buses.
V. Rajaraman/IISc. Bangalore
Indian Institute of Science Bangalore
M7/V1/July 04/3
Prof. V.Rajaraman
System Analysis and Design
System Analysis and Design /Data Oriented Systems Design
Pointers
References
1. Most of the material in this module has been adapted from the book “Analysis and
Design of Information Systems”, 2nd Edition, by V.Rajaraman, Prentice Hall of
India, 2003. Chapter 5 (pp. 49-52) and Chapter 11 (pp.154-170).
2. Good material on Data Dictionary is found in K.E.Kendall and J.E.Kendall ,
“Systems Analysis and Design”, 5th Edition, Pearson Education Asia, 2003.
Chapter 10 on Data Dictionaries. Chapter 16 Designing Effective Input.
V. Rajaraman/IISc. Bangalore
Indian Institute of Science Bangalore
M7/V1/July 04/1

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