Slide 1 Chapter 10 System Architecture Design Chapter 10 Alan Dennis, Barbara Wixom, and David Tegarden John Wiley & Sons, Inc. Slides by Fred Niederman Edited by Solomon Negash

Slide 2 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).

Slide 3 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 4 COMPUTING ARCHITECTURES

Slide 5 Functions of the Application System Data storage Data access logic Application logic Presentation logic

Slide 6 Architectures Server based Client based Client-server based

Slide 7 Alternative Servers In server based architectures, the servers do the work and present the results Mainframe Minicomputer Microcomputer (personal computer)

Slide 8 Server-Based Computing

Slide 9 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 10 Client-Based Computing

Slide 11 Client-Server-Based Computing (2 Tiers)

Slide 12 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

Slide 13 Client-Server -- Three Tiers

Slide 14 Client-Server -- Four Tiers

Slide 15 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

Slide 16 Distributed Objects Computing Middleware between clients and servers Update middleware when changing client code May reduce efficiency of the application CORBA DCOM

Slide 17 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 18 Selecting a Computing Architecture Server-BasedClient-basedClient-server Cost of infrastructureVery highMediumLow Cost of developmentMediumLowHigh Ease of developmentLowHighLow-medium Interface capabilitiesLowHighHigh Control and securityHighLowMedium ScalabilityLowMediumHigh

Slide 19 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 20 INFRASTUCTURE DESIGN

Slide 21 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 22 Top-Level Network Model

Slide 23 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 24 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 25 GLOBAL ISSUES

Slide 26 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 27 SECURITY

Slide 28 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 29 Most Common Threats

Slide 30 Assessing the Risk of Each Threat

Slide 31 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 32 Additional Controls Include A security policy Passwords and encryption Firewalls

What sort of computer architecture would you recommend for your project? Explain your preference.

Slide 34 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.