1. Systems Analysis and Design
Alan Dennis, Barbara Wixom, and David Tegarden
John Wiley & Sons, Inc.
Slides by Fred Niederman
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2. Copyright © 2001 John Wiley & Sons, Inc.
All rights reserved. Reproduction or translation of this work beyond that permitted in Section 117 of the 1976 United States Copyright Act without the express written permission of the copyright owner is unlawful.
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3. System Architecture Design
Chapter 10
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4. 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 (client-server based).
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5. 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.
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6. COMPUTING ARCHITECTURES
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7. Functions of the Application System
Data storage
Data access logic
Application logic
Presentation logic
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8. Architectures Server based Client based Client-server based
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9. Alternative Servers
In server based architectures, the servers do the work and present the results
Mainframe
Minicomputer
Microcomputer (personal computer)
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10. Server-Based Computing
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11. 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)
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12. Client-Based Computing
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13. Client-Server-Based Computing (2 Tiers)
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14. Client-Server Attributes
Typical Pros
Compatible with web-based system design
Scaleable
Work with multiple vendors/products
No central point of failure
Typical Cons/Limits
Complexity
New programming languages and techniques (stress for personnel)
More complex to update
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15. Client-Server -- Three Tiers
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16. Client-Server -- Four Tiers
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17. N-Tiered Client-Server Attributes
Typical Pros
Separates processing to better balance load
More scaleable
Typical Cons/Limits
Greater load on the network
More difficult to program and test
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18. Distributed Objects Computing
Middleware between clients and servers
Update middleware when changing client code
May reduce efficiency of the application
CORBA
DCOM
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19. 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
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20. 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
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21. 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?
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22. INFRASTUCTURE DESIGN
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23. 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
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24. Top-Level Network Model
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25. 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
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26. 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
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27. GLOBAL ISSUES
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28. 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
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29. SECURITY
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30. 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
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31. Most Common Threats
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32. Assessing the Risk of Each Threat
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33. Creating Controls
A control is something that mitigates or stops a threat
Controls include
redundancy
fault tolerant servers
disaster recovery plans
anti-virus software
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34. Additional Controls Include
A security policy
Passwords and encryption
Firewalls
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35. Explain your preference.
CD Selections
What sort of computer architecture would you recommend for CD Solutions?
Explain your preference.
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36. 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.
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37. Expanding the Domain
To contrast the approaches of CORBA and DCOM/COM from Microsoft, check the following websites:
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