System Architecture Design
Chapter 10
Slide 1
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Systems Analysis and Design
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Key Definitions
The system architecture design consists
of plans for the hardware, software,
communications, security , and global
support for the new application
The designers must decide if processing
will occur in the server (server-based), at
the personal computer (client-based), or
in some combination of these (clientserver based).
Slide 2
PowerPoint Presentation for Dennis, Wixom & Tegardem
Systems Analysis and Design
Copyright 2001 © John Wiley & Sons, Inc. All rights reserved.
Key Definitions
The network model shows major
components of the system, where
they are located and how they will
be connected to one another.
The hardware and software
specifications describe these
components in detail and aid those
responsible for purchase and
acquisition of these products.
Slide 3
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Systems Analysis and Design
Copyright 2001 © John Wiley & Sons, Inc. All rights reserved.
COMPUTING
ARCHITECTURES
Slide 4
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Systems Analysis and Design
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Functions of the
Application System
Data storage
Data access logic
Application logic
Presentation logic
Slide 5
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Systems Analysis and Design
Copyright 2001 © John Wiley & Sons, Inc. All rights reserved.
Architectures
Server based
Client based
Client-server based
Slide 6
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Systems Analysis and Design
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Alternative Servers
In server based architectures,
the servers do the work and
present the results
Mainframe
Minicomputer
Microcomputer (personal
computer)
Slide 7
PowerPoint Presentation for Dennis, Wixom & Tegardem
Systems Analysis and Design
Copyright 2001 © John Wiley & Sons, Inc. All rights reserved.
Server-Based Computing
Slide 8
PowerPoint Presentation for Dennis, Wixom & Tegardem
Systems Analysis and Design
Copyright 2001 © John Wiley & Sons, Inc. All rights reserved.
Alternative Clients
In client based architectures, clients
do most of the work (except data
storage) and present the results
Terminals
Microcomputer (personal computer)
Special purpose terminals
(ATMs, kiosks, Palm Pilots,
and many others)
Slide 9
PowerPoint Presentation for Dennis, Wixom & Tegardem
Systems Analysis and Design
Copyright 2001 © John Wiley & Sons, Inc. All rights reserved.
Client-Based Computing
Slide 10
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Systems Analysis and Design
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Client-Server-Based
Computing (2 Tiers)
Slide 11
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Systems Analysis and Design
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Client-Server Attributes
Typical Pros
Compatible with
web-based system
design
Scaleable
Work with multiple
vendors/products
No central point of
failure
Slide 12
Typical
Cons/Limits
Complexity
New programming
languages and
techniques (stress
for personnel)
More complex to
update
PowerPoint Presentation for Dennis, Wixom & Tegardem
Systems Analysis and Design
Copyright 2001 © John Wiley & Sons, Inc. All rights reserved.
Client-Server -- Three
Tiers
Slide 13
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Systems Analysis and Design
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Client-Server -- Four Tiers
Slide 14
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Systems Analysis and Design
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N-Tiered Client-Server
Attributes
Typical Pros
Separates
processing to
better balance
load
More scaleable
Slide 15
Typical
Cons/Limits
Greater load on
the network
More difficult to
program and
test
PowerPoint Presentation for Dennis, Wixom & Tegardem
Systems Analysis and Design
Copyright 2001 © John Wiley & Sons, Inc. All rights reserved.
Distributed Objects
Computing
Middleware between clients and
servers
Update middleware when changing
client code
May reduce efficiency of the
application
CORBA
DCOM
Slide 16
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Systems Analysis and Design
Copyright 2001 © John Wiley & Sons, Inc. All rights reserved.
Realities of Infrastructure
Design
Most often the infrastructure
will be in place
Coordination of infrastructure
components is very complex
The application developer will
need to coordinate with
infrastructure specialists
Slide 17
PowerPoint Presentation for Dennis, Wixom & Tegardem
Systems Analysis and Design
Copyright 2001 © John Wiley & Sons, Inc. All rights reserved.
Selecting a Computing
Architecture
Server-Based
Client-based
Client-server
Cost of infrastructure
Very high
Medium
Low
Cost of development
Medium
Low
High
Ease of development
Low
High
Low-medium
Interface capabilities
Low
High
High
Control and security
High
Low
Medium
Scalability
Low
Medium
High
Slide 18
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Systems Analysis and Design
Copyright 2001 © John Wiley & Sons, Inc. All rights reserved.
Your Turn
Consider the course registration
system at your university:
What computing architecture does it
use?
What computing architecture would
you use if you were replacing it
today?
Slide 19
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Systems Analysis and Design
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INFRASTUCTURE
DESIGN
Slide 20
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Systems Analysis and Design
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The Network Model
No standard format
Conveys complexity of the system
and how components fit together
Components are
Clients
Equipment
Connection to external systems or
networks
Slide 21
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Systems Analysis and Design
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Top-Level Network Model
Slide 22
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Systems Analysis and Design
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Hardware and Software
Specification
Used if new hardware or
software must be purchased
Actual acquisition of hardware
and software usually left to a
purchasing department -especially in larger firms
Slide 23
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Systems Analysis and Design
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Steps in Hardware and
Software Specification
Note hardware in low-level network
model to create list of needed hardware
Describe equipment in as much detail as
possible
Consider whether increased processing
and traffic will absorb unused hardware
capacity
Note all software running on each
hardware component
Slide 24
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Systems Analysis and Design
Copyright 2001 © John Wiley & Sons, Inc. All rights reserved.
GLOBAL ISSUES
Slide 25
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Systems Analysis and Design
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Global Requirements
Multilingual requirements
Concurrent multilingual systems
Discrete multilingual systems
Local versus centralized control
Unstated norms (e.g. dates,
currency)
24-7 Support
Communications infrastructure
Slide 26
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Systems Analysis and Design
Copyright 2001 © John Wiley & Sons, Inc. All rights reserved.
SECURITY
Slide 27
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Systems Analysis and Design
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Identifying Threats to the
System
A threat is any potential adverse
occurrence that can do harm to the
application or its data
Threats come from internal as well
as external sources
Categories of threats
Disruptions, destruction and disaster
Unauthorized access
Slide 28
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Systems Analysis and Design
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Most Common Threats
Slide 29
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Systems Analysis and Design
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Assessing the Risk of Each
Threat
Slide 30
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Systems Analysis and Design
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Creating Controls
A control is something that
mitigates or stops a threat
Controls include
redundancy
fault tolerant servers
disaster recovery plans
anti-virus software
Slide 31
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Systems Analysis and Design
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Additional Controls
Include
A security policy
Passwords and encryption
Firewalls
Slide 32
PowerPoint Presentation for Dennis, Wixom & Tegardem
Systems Analysis and Design
Copyright 2001 © John Wiley & Sons, Inc. All rights reserved.
What sort of computer
architecture would you
recommend for CD Solutions?
Explain your preference.
PowerPoint Presentation for Dennis, Wixom & Tegardem
Systems Analysis and Design
Copyright 2001 © John Wiley & Sons, Inc. All rights reserved.
Summary
The three fundamental computing
architectures are server-based, client-based,
and client-server based.
The network model shows technical
components of the system and their
geographic location throughout the
organization.
Hardware and software must be specified for
acquisition in the project
The systems analyst needs to also account
for global issues and security measures.
Slide 34
PowerPoint Presentation for Dennis, Wixom & Tegardem
Systems Analysis and Design
Copyright 2001 © John Wiley & Sons, Inc. All rights reserved.
Expanding the Domain
To contrast the approaches of
CORBA and DCOM/COM from
Microsoft, check the following
websites:
http://www.corba.org
http://www.microsoft.com/com
Slide 35
PowerPoint Presentation for Dennis, Wixom & Tegardem
Systems Analysis and Design
Copyright 2001 © John Wiley & Sons, Inc. All rights reserved.