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Slide 1
System Architecture Design
Chapter 10Chapter 10
Alan Dennis, Barbara Wixom, and David Tegarden
John Wiley & Sons, Inc.
Slides by Fred NiedermanEdited 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 applicationThe 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 storageData access logicApplication logicPresentation logic
Slide 6
Architectures
Server basedClient basedClient-server based
Slide 7
Alternative Servers
In server based architectures, the servers do the work and present the resultsMainframeMinicomputerMicrocomputer (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 resultsTerminalsMicrocomputer (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 ProsCompatible with web-based system designScaleableWork with multiple vendors/productsNo central point of failure
Typical Cons/Limits
ComplexityNew 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 ProsSeparates processing to better balance loadMore scaleable
Typical Cons/Limits
Greater load on the networkMore difficult to program and test
Slide 16
Distributed Objects Computing
Middleware between clients and serversUpdate middleware when changing client codeMay reduce efficiency of the applicationCORBADCOM
Slide 17
Realities of Infrastructure Design
Most often the infrastructure will be in placeCoordination of infrastructure components is very complexThe application developer will need to coordinate with infrastructure specialists
Slide 18
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 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 formatConveys complexity of the system and how components fit togetherComponents are
ClientsEquipmentConnection 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 purchasedActual 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 hardwareDescribe equipment in as much detail as possibleConsider whether increased processing and traffic will absorb unused hardware capacityNote all software running on each hardware component
Slide 25
GLOBAL ISSUES
Slide 26
Global Requirements
Multilingual requirementsConcurrent multilingual systemsDiscrete multilingual systems
Local versus centralized controlUnstated norms (e.g. dates, currency)24-7 SupportCommunications 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 dataThreats come from internal as well as external sourcesCategories of threats
Disruptions, destruction and disasterUnauthorized 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 threatControls include
redundancyfault tolerant serversdisaster recovery plansanti-virus software
Slide 32
Additional Controls Include
A security policyPasswords and encryptionFirewalls
What sort of computer architecture would you recommend for your project?Explain your preference.
Slide 34
SummaryThe 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 projectThe systems analyst needs to also account for global issues and security measures.
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