BITG 2323: WEEK 2
Database System
Development
Lifecycle
(SDLC)
• Information and database system
development lifecycle (DbLC)
• Relational Data model

Database System Development Lifecycle

The System Design Life Cycle (SDLC) illustrates the
life cycle of an information system. It is the overall or
big picture of what has and what will historically
happen to the system.
The Database Life Cycle (DBLC) likewise exhibits
the life cycle of a database within an information
system.
SDLC & DbLC
Information &
Db System
Lifecycle
Introduction

SDLC
Information &
Db System
Lifecycle
Phases

DbLC
Information &
Db System
Lifecycle
Phases
Initial Study
Design
Implement
& Loading
Test &
Evaluate
Operation
Maintenance
& Evaluation

SDLC & DbLC
Information &
Db System
Lifecycle
Parallel Activities

SDLC & DbLC
Information &
Db System
Lifecycle
Parallel Activities

Training Technology Company
Overall current system description
The administrator accepts job applicants, types their CVs and
files it in applicants file. Administrator goes through TEMP-
STAFF files, collecting relevant information about temporary
instructor’s class and time table.The company also compiles
reports on instructors based on feedback information
received from students. Every end of course session, these
instructors will hand in students marks and their time sheets
to the administrator in order to get their pay. There are no
formal methods of documenting the temporary instructors’
performance in the various placements made by the
company. The reports received were usually informal
comments received over a phone and were not
systematically recorded.
DbLC
Information &
Db System
Lifecycle
Initial Study
Problem and
Constraints
Initial Study
• Analyse company situation
• Define problems & constraints
• Define objective
• Define scope & boundaries

DbLC
Information &
Db System
Lifecycle
Initial Study
Initial Study
• Analyse company situation
• Define problems & constraints
• Define objective
• Define scope & boundaries

Training Technology Company
1. Automated business system
2. Manage and track :
• class registration
• class schedule
• instructor availability
mission
DbLC
Information &
Db System
Lifecycle
Initial Study
Initial Study
• Analyse company situation
• Define problems & constraints
• Define objective
• Define scope & boundaries

• How does the existing system function?
• What input does the system require?
• What documents does the system generate?
• How is the system output used? By Whom?
• What are the operational relationships among business units?
• What are the limits and constraints imposed on the system?
DbLC
Information &
Db System
Lifecycle
Initial Study
Initial Study
• Analyse company situation
• Define problems &
constraints
• Define objective
• Define scope & boundaries

Define
Objective
from manual to Auto
user able to access database
instructor able to query and
make changes to data
student able to query online
Initial Study
• Analyse company situation
• Define problems & constraints
• Define objective
• Define scope & boundaries
DbLC
Information &
Db System
Lifecycle
Initial Study

Scope and
Boundaries
How big is the system required?
Budget
Hardware and Software Requirement
Organizational change / extent
Must correspond to those envisioned by end
users
• What is proposed system’s initial objective?
• Will system interface with other systems in the
company?
• Will system share data with other systems or users?
Database
System
Objectives
Initial Study
• Analyse company situation
• Define problems & constraints
• Define objective
• Define scope & boundaries
DbLC
Information &
Db System
Lifecycle
Initial Study

DbLC
Information &
Db System
Lifecycle
Design
Design
• Create conceptual design
• DBMS software selection
• Create logical design
• Create physical design

DbLC
Information &
Db System
Lifecycle
Database Design Process
Conceptual Logical
Physical
DBMS Selection
• Data analysis and
requirements
• Entity
relationship
modeling and
normalization
• Data model
verification
• Distributed
database design
• Define tables,
columns,
relationships &
constraints
• Normalized set of
tables
• Ensure entity and
referential integrity;
define column
constraints
• Ensure the model
supports user
requirements
• Common factors affecting
purchasing decisions:
– Cost
(Purchase, maintenance,
operational, license,
installation, training, and
conversion costs.)
– DBMS features and
tools
(report generators etc.)
– Underlying model
(Relational/OO)
– Portability
(Platforms, systems, and
languages)
– DBMS hardware
requirements
•Process of selecting
the data storage and
data access
characteristics of the
database (integrity
and security
measures).
•It affects not only
the location of the
data in the storage
device(s) but also
the performance :
e.g.
– Storage
media
– Seek time
Design
• Create conceptual design
• DBMS software selection
• Create logical design
• Create physical design

DbLC
Information &
Db System
Lifecycle
Implementation and Loading
• Implement all design specifications from previous
phase:
–Install the DBMS
•V creates logical representations of computing
resources independent of physical resources
–Create the Database
–Load or Convert the Data
Implementation and Loading
• Install DBMS
• Create databases
• Load or convert data

DbLC
Information &
Db System
Lifecycle
Testing and Evaluation
•Occurs in parallel with applications programming
•If implementation fails to meet some of system’s evaluation criteria:
–Fine-tune specific system and DBMS configuration parameters
–Modify physical or logical design
–Upgrade software and/or hardware platform
•Integrity
–Enforced via proper use of primary, foreign key rules
•Backup and Recovery
–Full backup
–Differential backup
–Transaction log backup
Testing and Evaluation
• Test database
• Fine-tune database
• Evaluate database and its apps.

• Once database has passed evaluation stage, it is
considered operational
• Beginning of operational phase starts process of
system evolution
• Problems not foreseen during testing surface
• Solutions may include:
–Load-balancing software to distribute transactions
among multiple computers
–Increasing available cache
DbLC
Information &
Db System
Lifecycle
Operation
Operation
• Produce the required information flow

DbLC
Information &
Db System
Lifecycle
Maintenance and Evaluation
• Required periodic maintenance:
–Preventive maintenance (backup)
–Corrective maintenance (recovery)
–Adaptive maintenance
–Assignment of access permissions and their maintenance
for new and old users
–Generation of database access statistics
–Periodic security audits
–Periodic system-usage summaries
Maintenance and Evolution
• Introduce changes
• Make enhancements

• Information system facilitates transformation of data into information
– Manages both data and information
• SDLC traces history (life cycle) of an application within the information
system
• DBLC describes history of database within the information system
• Database design and implementation process moves through series of
well-defined stages
SUMMARY

Relational Database Model

• Relational model
–View data logically rather than physically
• Table
–Structural and data independence
–Resembles a file conceptually
• Relational database model is easier to
understand than hierarchical and network
models
Relational Database Model
Relational
Database
Model
A Logical View of Data

Relational Database Model
Tables and Their Characteristics
• Logical view of relational database is based on
relation
–Relation thought of as a table
• Table: two-dimensional structure composed of
rows and columns
• Contains group of related entities (entity set)
Relational
Database
Model

Relational Database Model
Relational
Database
Model

Keys
Types
• Each row in a table must be uniquely identifiable
• Key: one or more attributes that determine other attributes
–Key’s role is based on determination
•If you know the value of attribute A, you can
determine the value of attribute B
–Functional dependence
•Attribute B is functionally dependent on A if all rows
in table that agree in value for A also agree in value
for B
Relational
Database
Model

• Entity integrity
– Each row (entity instance) in the table has its own unique identity
• Nulls
– No data entry
– Not permitted in primary key
– Should be avoided in other attributes
• Controlled redundancy
– Makes the relational database work
– Tables within the database share common attributes
•Enables tables to be linked together
– Multiple occurrences of values not redundant when required to
make the relationship work
– Redundancy exists only when there is unnecessary duplication of
attribute values
Keys
Types
Relational
Database
Model

SUPERKEY
CANDIDATE
PRIMARY
FOREIGN
COMPOSITE
A Super key is any combination of fields within a table that
uniquely identifies each record within that table.
it is an attribute or set of attribute that can be selected as
primary key for a table to uniquely identify each record in
that table
is a candidate key that is most appropriate to become main
key to uniquely identify each record in a table
key that consist two or more attributes that uniquely
identify an entity assurance
A foreign key is generally a primary key from one table that
appears as a field in another where the first table has a
relationship to the second.
Keys
Types
Relational
Database
Model

Consider a Relation or Table R1. Let A,B,C,D,E are the attributes of this
relation.
A→B,C,D,E
This means the attribute 'A' uniquely determines the other attributes B,C,D,E.
B,C→A,D,E
This means the attributes 'BC' jointly determines all the other attributes A,D,E
in the relation.
Primary Key : A
Candidate Keys : A, BC
Super Keys : A,BC,ABC,AD
Keys
Types - Example
Relational
Database
Model
R(A,B,C,D,E)

SUPERKEY
CANDIDATE
PRIMARY
FOREIGN
COMPOSITE
First Name Last Name gender
ZULAIKHA AFFENDI F
ZULAIKHA AFFENDI F
Keys
Types
Relational
Database
Model
There are two people with same name! Which one is which?
A Super key is any combination of fields within a table that uniquely
identifies each record within that table.
For example, the super key can be a combination of a name, phone number,
address and b.o.d
This would always be unique unless 2 people with the same name lived in the
same place with the same phone number

SUPERKEY
CANDIDATE
PRIMARY
FOREIGN
COMPOSITE
First Name Last Name gender SSN phone number
Keys
Types
Relational
Database
Model
Candidate key is a partial of the super key. If
super key is already the least amount of columns
then, both the superkey and the candidate key
will be the same thing.
Candidate key Superkey

SUPERKEY
CANDIDATE
PRIMARY
FOREIGN
COMPOSITE
s_id s_name age course address
Primary Key
cust_id order_id sale_detail
Composite Key
Keys
Types
Relational
Database
Model

NULL VALUE • Many RDBMs
enforce
integrity rules
automatically
• Safer to ensure
that application
design conforms
to entity and
referential
integrity rules
• Designers use
flags to avoid
nulls
– Flags indicate
absence of
some value
Integrity Rules
Relational
Database
Model

The Data Dictionary
and System Catalog
• Data dictionary
– Provides detailed accounting of all tables found within the
user/designer-created database
– Contains (at least) all the attribute names and characteristics for
each table in the system
– Contains metadata: data about data
• System catalog
– Contains metadata
– Detailed system data dictionary that describes all objects within the
database
Relational
Database
Model

Relationship
Types
1:M 1:1 M:N
• One entity related to
only one other
entity, and vice
versa
• Sometimes means
that entity
components were
not defined properly
• Could indicate that
two entities actually
belong in the same
table
• Certain conditions
absolutely require
• Cannot be
implemented
as such in the
relational
model
• M:N
relationships
can be
changed into
1:M
relationships
• Relational
modeling ideal
• Should be the
norm in any
relational
database design
Relational
Database
Model

Relationship
Types
An(one) Author writes many Books
A Student leads many student
………….
…..
Relational
Database
Model

ERD
Notation
Relational
Database
Model

Data
Redundancy
•It is crucial
•When data stored is not consistant
•A well design of DBMS can help to reduce data redundancy
•Errors more likely to occur when complex data entries are made in
several different files
•Error also occur if data recur frequently in one or more files
• Data redundancy leads to data anomalies
– Can destroy the effectiveness of the database
• Foreign keys
– Control data redundancies by using common attributes shared by
tables
• Sometimes, data redundancy is necessary
Relational
Database
Model

•data anomalies occur when the data to be entered into the system
does not work as expected. This usually happens when database
consist of redundant data.
•3 Types :
• UPDATE
occurs when changes cannot be completed to the existing
records.
• INSERTION
occurs when new record cannot be entered into the system.
• DELETION
occurs when deleted historical data cannot be traced after
deletion of certain data take place.
Data
Anomalies
Relational
Database
Model

• Orderly arrangement to logically access rows in a table
• Index key
– Index’s reference point
– Points to data location identified by the key
• Unique index
– Index in which the index key can have only one
pointer value (row) associated with it
• Each index is associated with only one table
Indexes
Relational
Database
Model

SUMMARY
• Each table row must have a primary key that uniquely identifies
all attributes
• Tables are linked by common attributes
• The relational model supports relational algebra functions
–SELECT, PROJECT, JOIN, INTERSECT UNION,
DIFFERENCE, PRODUCT, DIVIDE
• Good design begins by identifying entities, attributes, and
relationships
–1:1, 1:M, M:N

DISCUSSION
Consider the relational database of next relational schema with 3
relations. Underline the best possible primary keys in each relation?
EMPLOYEE (person_name, street, city)
WORKS (person_name, company_name, salary)
COMPANY (company_name, city)