Transcript Process Modelling - Monash University

IMS2805 - Systems Design and
Implementation
Lecture 13
Revision
13.1
Revision
 System concepts and information systems
 The Systems Development Life Cycle (SDLC)
 The design and implementation phases of the
systems development life cycle:
 Systems analysis issues and techniques covered
in previous units:
information gathering
process modelling
data modelling
13.2
Revision
 Design and implementation issues and techniques:
generating and evaluating design alternatives
system architecture; finalising design specifications
interface design
implementation - testing, conversion,
acceptance planning, documentation
maintenance
 General systems development issues
communication and documentation
quality issues
13.3
Information systems
 An Information System is a formal
arrangement of people, data, processes
integrated to help manage complexity and
to support and improve business
operations, as well as supporting the
problem-solving and decision-making
activities of managers.
 It transforms Data into Information
13.4
Systems development and the
SDLC
 The need to build new information systems or
change existing ones comes about because:
 there are problems in the way in which
existing systems operate; or
 changes in circumstances create
opportunities to improve things by doing them
differently; or
 there are external requirements or pressures,
e.g. new government legislation
13.5
The Systems
Development Life Cycle
The SDLC provides:
 a systematic and orderly approach to solving business
problems
 a means of managing, directing, monitoring and
controlling the process of system building, including:
 a description of the process - steps to be followed
 deliverables - reports/programs/documentation/etc
 milestones - dates of completion of steps or
deliverables
13.6
Systems Development Phases
Analysts Role
Initiation
Analysis
Design
Implementation
Documentation
Ethics
Project Management
Review
Maintenance
13.7
Systems Development
Activities involved in building computerbased information systems are: identifying problems
 analysing and describing information and
processing needs
 designing solutions to meet those needs
 acquiring/building new systems
 implementing new systems
 maintaining information systems
13.8
The relational database model
 The relational database model represents
data in the form of tables or relations
 Important concepts are:
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relation
primary key
foreign key
functional dependency
normalisation
13.9
System Architecture
 System architecture is concerned with the technical and
organisational configuration of the design of an
application system
 An architecture is a set of definitions, rules, and terms
that are used as guidelines for building a product
 The architecture must be consistent with: budget constraints
 organisational constraints
 structure
 management
 existing technology
 requirements identified by analysis
13.10
System Architecture Components
 Processing
 Data
 Communications/networks
These components are interrelated
and must be considered in
conjunction with each other.
13.11
Client/Server Architecture—
The Clients
A client/server system is a solution in which
the presentation, presentation logic, application
logic, data manipulation, and data layers are
distributed between client PCs and one or more
servers.
A thin client is a personal
computer that does not have to be
very powerful (or expensive) in
terms of processor speed and
memory because it only presents
the user interface to the user.
A fat client is a personal computer
or workstation that is typically more
powerful (and expensive) in terms
of processor speed, memory, and
storage capacity. Most PCs are
considered to be fat clients.
(From WHITTEN, J.L., BENTLEY, L.D. and DITTMAN, K.C. (2001) 5th ed.,
Systems Analysis and Design Methods, Irwin/McGraw-Hill, New York, NY, Chapter 11.)
13.12
Human–Computer
Interface Design
The interface is the link between the users and the computer
Database
Programs
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end user
direct user
To many users the interface is the system
13.13
The Basics of Interface
Design
Five Principles or “Commandments”:
 Support “Transportability of Knowledge”
 Be Consistent
 Provide Feedback
 Use Drab Colours
 Make the User Boss
13.14
Implementing the System
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implementation planning
Build and test software
Build/modify databases, networks etc.
finalise documentation
prepare the site
convert data into required form and
media
conduct training
install system
monitor system
transition to maintenance mode
post-implementation review
13.15
Stages of Testing
Installation test
system in use
Acceptance test
accepted system
Performance
test
validated software
Function test
functioning system
Integration test
integrated modules
Unit (module)
test
tested modules
13.16
Install the System
ALTERNATIVES:
• Direct installation or Abrupt cut-over;
• Parallel installation;
• Phased installation or Staged installation;
• Pilot installation or Single Location conversion.
13.17
Maintenance
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Corrective - fix errors
Adaptive - satisfy changing needs
Perfective - enhance performance
Preventative - fix potential problems
 If the cost of maintenance is too high consider
other options:
 new development, purchase a software
package, re-engineer/modify
13.18
Documentation
 Not necessarily a piece of paper.
 Any permanent medium used to communicate to other people
can be classed as documentation
 Product and documentation should be developed at the same
time
 DOCUMENTATION IS PART OF THE PRODUCT
Documentation is communication:
 the objective is to:
 create a specific effect
 on particular readers
 who want specific information,
 have particular characteristics and
 will read under particular circumstances.
13.19
Quality in systems development
 various definitions e.g.
Ability to satisfy stated/implied needs
 the cost of detecting and correcting errors
rises greatly during the SDLC
 must be embedded in the systems development
process: product and process
 implementing quality: e.g. standards, technical
reviews
13.20