1. Chapter 9

2. Chapter Objectives
Provide a checklist of issues to consider when selecting a system architecture
Describe servers, server-based processing, clients, and client-based processing
Explain client/server architecture, including tiers, cost-benefit issues, and performance
Compare in-house e-commerce development to packaged solutions 3

3. Chapter Objectives
Explain the difference between online and batch processing
Define network topology, and provide examples of hierarchical, star, bus, and ring network models
Describe wireless network standards, advantages, and disadvantages 3

4. Chapter Objectives Explain network protocols and licensing issues
Explain performance measurement, fault management, backup, and disaster recovery
Describe the systems design specification

5. Introduction
An effective system combines elements into an architecture, or design, that is flexible, cost-effective, technically sound, and able to support the information needs of the business
System architecture translates the logical design of an information system into a physical structure that includes hardware, software, network support, and processing methods 4

6. System Architecture Checklist
The analyst must consider seven specific issues that will affect the architecture choice
Enterprise resource planning (ERP)
Initial and total cost of ownership (TCO)
Scalability
Web integration
Legacy system interface requirements
Processing options
System security

7. System Architecture Checklist
Enterprise Resource Planning (ERP)
The objective of ERP is to establish a company-wide strategy for using IT resources
Advantage: it describes a specific hardware and software environment ( platform) that ensure connectivity and easy integration of future system including in house software and commercial packages
Supply chain management

8. System Architecture Checklist
Initial Cost and TCO
Ask questions like the following
If in-house development was selected as the best alternative initially, is it still the best choice?
If a specific package was chosen initially, is it still the best choice?
Answers might affect the initial cost and TCO for the proposed system

9. System Architecture Checklist
Scalability
Scalability, also called extensibility, refers to a system’s ability to expand, change or downsize easily to meet the changing need of a business enterprise
Especially important in implementing systems that are volume-rated, such as transaction processing systems

10. System Architecture Checklist
Web Integration
An information system includes applications
Web-centric architecture that follows internet design protocols and enables a company to integrate the new application into its e-commerce strategy.
Avoids many of the connectivity and compatibility problems that typically arise
IBM uses E-marketplaces to describe internet based solutions that allow seller and buyers to automate procurement process and achieve substantial benefits

11. System Architecture Checklist
Legacy System Interface Requirements
The new system might have to interface with one or more legacy systems
Interfacing a new system with legacy systems involves analysis of data formats and compatibility
The analyst must know if the new application eventually will replace the legacy system

12. System Architecture Checklist
Processing Options
In planning the architecture, designers also must consider how the system will process data - online or in batches
Provision must be made for backup and speedy recovery in the event of system failure

13. System Architecture Checklist
Security Issues
Security is a concern at every stage of system development
Web-based systems introduce additional security concerns

14. Planning the Architecture
Every information system involves three main functions:
Data storage and access methods
Application programs to handle the processing logic
An interface that allow users to interact with system.
Depending on the architecture the three function are performed on a server, on a client, or are divided between the server and the client.

15. Planning the Architecture
Servers
Server is a computer that supplies data, processing services, or other support to one or more computers called client
The term mainframe architecture typically describes a multiuser environment where the server is significantly more powerful than the clients

16. Planning the Architecture
Server-based processing
In a centralized design, the remote user’s keystrokes are transmitted to the mainframe, which responds by sending screen output back
Today mainframe architecture used in credit card company or in bank.

17. Planning the Architecture
Clients
Stand-Alone Computing
Stand-alone computing was inefficient and expensive
Maintaining data on individual workstations raised major concerns about data security, integrity, and consistency
It was impossible to protect and back up valuable business data, and companies were exposed to enormous risks
This led to data inconsistency and unreliability

18. Planning the Architecture
Local and wide area networks
Most of the companies resolved the problems of stand alone computing by joining clients into local area network that allows sharing of data and hardware recourses.
A wide area network (WAN) spans long distances and can connect LANs that are continents apart
The network is transparent
Compared to mainframe architecture, distributed systems increase concerns about data security and integrity

19. Planning the Architecture
Clients
Client-based processing

20. Client/Server Architecture
Overview
Client/server architecture refers to system that divide processing between one or more networked clients and a central server.
In typical client/server system, the client handles the entire user interface, including data entry, data query, and screen presentation logic.
The server stores the data and provides data access and database management functions.

21. Client/Server Architecture
Overview
The early client/server system was expensive.
Few clear standards exist
client needed powerful hardware and software to handle shared processing tasks.
Many companies had an installed base of mainframe data, called legacy data, which was difficult to access and transport to a client/server environment
The client/server concept continues to expand to include clients and servers outside the organization

23. Client/Server Architecture
Client/Server Design Styles
Depends on the style the processing is divided between the server and the clients
The nature of communication is depends on the type of the server
A database server process individual SQL commands.
The transaction server handles a set of SQL commands.
An object server exchanges object messages with clients.
A web server sends and receives Internet based communication.

24. Client/Server Architecture
A web server sends and receives Internet based communication.

25. Client/Server Architecture
Types of Clients: Fat and Thin
A fat client also called a thick client design locates all or most of the application processing logic at client.
A thin client design locates all or most of the processing logic at the server.
The table in next slide describes the characteristics of the fat and thin clients.

26. Client/Server Architecture
Types of Clients: Fat and Thin

27. Client/Server Architecture
Client/Server Tiers
Two-tier designs
The user interface resides on the client, all data resides on the server, and the application logic can run either on the server or on the client or be divided between the client and server.
Three-tier design – n-tier designs
The user interface runs on the client and the data stored on the server, a middle layer process the client requests and translates them into data access commands that can be understood and carried out by the server

28. Client/Server Architecture
Client/Server Tiers
Three-tier design – n-tier designs
Think of the middle layer as an application server, because it provides the application logic, or business logic
The middle layer is more efficient and cost-effective in large-scale systems

29. Client/Server Architecture
Middleware
Enables the tiers to communicate and pass data back and forth
Provides a transparent interface that enables system designers to integrate dissimilar software and hardware
Can integrate legacy systems and Web-based applications

30. Client/Server Architecture
Cost-Benefit Issues
Client/server systems enable the firm to scale the system in a rapidly changing environment
Client/server computing also allows companies to transfer applications from expensive mainframes to less expensive client platforms
Client/server systems reduce network load and improve response times

31. Client/Server Architecture
Client/Server Performance Issues
In contrast to the centralized system, a client/server design separates applications and data
Client/server systems must be designed so the client contacts the server only when necessary

32. Client/Server Architecture
Client/Server Performance Issues
Another issue is the data storage. Data can be stored in in more than one location using Distributed database management system (DDBMS) . DDBMS has the following advantages:
Data stored closer to users can reduce network traffic
The system is scalable, so new data sites can be added without reworking the system design
The system is less likely to experience catastrophic failure

33. Client/Server Architecture
Client/Server Performance Issues
DDBMS has also the following disadvantages:
It can be more difficult to maintain controls and standards when data is stored in various locations
The architecture of DDBMS is more complex and difficult to manage.

34. Internet-Based Architecture
Developing E-Commerce Solutions In-House

35. Internet-Based Architecture
Packaged Solutions and E-commerce Service Providers
Many vendors offer ready to use systems for companies
Another alternative is to use an application service provider (ASP)
Must consider whether the advantage of lower initial cost outweighs the disadvantage of reduced flexibility later on

36. Internet-Based Architecture
Corporate Portals
A corporate portal can provide access for customers, employees, suppliers, and the public
Oracle and SAP offer powerful enterprise portal software

37. Processing Methods Online Processing
Online systems handles transactions when and where they occur and provide output directly to users
Example can be an airline reservation system and ATM system.

38. Processing Methods

39. Processing Methods Online Processing
Online processing systems have four typical characteristics:
The system processes transactions completely when and where they occur
Users interact directly with the information system
Users can access data randomly
The information system must be available whenever necessary to support business functions

40. Processing Methods Batch Processing
In a batch processing system, data is collected and processed in groups, or batches
The IT operations group can run batch programs on a predetermined schedule without user involvement; and Batch programs require significantly fewer network resources than online systems

41. Processing Methods Combined Online and Batch Processing
Online processing offers an inherent advantage because data is entered and validated as it occurs
Online processing is more expensive
Backup and recovery for online processing is more difficult
In many situations, batch processing is cost-effective, less vulnerable to system disruption, and less intrusive

42. Processing Methods Combined Online and Batch Processing
An example can be the Point of Sale (POS)

43. Network Models
A network allows the sharing of hardware, software, and data resources in order to reduce expenses and provide more capability to users.
When planning a network design, you must consider network terms and concepts, including the OSI model, network model tools, network topology, network protocol, licensing issues, and wireless network.

44. Network Models The OSI Reference Model
The Open System Interconnection (OSI) model which describes how data actually moves from an application on one computer to an application on another network, consists of seven layers
Network layer: defines network addresses and determines how data is routed over the network
Data link layer: defines specific methods of transmitting data over the physical layer, such as defining the start and end of a data block
Physical layer: contains physical components that carry data, such as cabling and connecters

45. Network Models
Each layer performs specific function, as follow:

46. Network Topology Ring network:
Resembles a circle of computers that communicate with each other.
Data flows in only one direction
One disadvantage is if a device fails, the devices downstream from the failed device cannot communicate with network

47. Hierarchical network:
Network Topology
Hierarchical network:
One or more powerful servers control the network
An example is retail chain, with central computer that stores data about sales activity and inventory levels and local computer handle store level operations.

48. Network Topology Bus network:
A single communication path connects the network server, departmental server, workstations, and peripheral device
An advantage is that devices can be attached or detached from the network at any point without disturbing the rest of the network.
Disadvantage is that the performance can decline as more devices added

49. Network Topology Star network:
Has a central computer with network devices connected to it
At the center of the star which is called hub, a central server manages the network
Disadvantage is that the entire network is depend on the central computer.

50. Network Models Network Protocols and Licensing Issues
The network must use a protocol
A popular network protocol is Transmission Control Protocol/Internet Protocol (TCP/IP)
A familiar example of a TCP/IP protocol is the file transfer protocol (FTP)

51. Network Models Wireless Networks
A wireless local area network, or WLAN
Uses protocol that is developed by Institute of Electrical and Electronics Engineers (IEEE)
This standard referred to Wi-Fi which stands for wireless fidelity
Although they have many advantages, wireless networks pose special concerns with regard to system security

52. Wireless Networks
Bluetooth is another wireless communication that is very popular for short distance wireless communication
On addition to protocols for LANs, IEEE is working on standards which is communication protocol for MANs (metropolitan area networks) these specification that IEEE calls Wireless MAN™ - WiMAX are expected to enable wireless multimedia applications with a range of up to 30 miles

53. System Management and Support
Performance Management
Performance management tools are designed to collect information about system resources and activity levels
Firms such as NetScout Systems offer comprehensive performance management packages
The NetScout Web site mentions studies that show network delays cost the industry more revenue than actual stoppages

54. System Management and Support
Fault Management, Backup, and Disaster Recovery
Fault management
Includes monitoring the system for signs of trouble, logging all system failures, diagnosing the problem, and applying corrective action

55. System Management and Support
Fault Management, Backup, and Disaster Recovery
Backup and disaster recovery
Backup
Recovery
Disaster recovery plan
Backup and recovery planning depends on the type of system involved

56. System Management and Support
Fault Management, Backup, and Disaster Recovery
Backup and disaster recovery
Another common strategy is to use a RAID (redundant array of independent disks) system
RAID systems are called fault-tolerant because the failure of any disk does not disable the system
Experienced IT professionals often note that the three most important system security tools are backup, backup, and more backup

57. Systems Design Completion
System Design Specification
A typical system design specification uses a structure similar to the following:
Executive summary (brief over view of the job)
System components (design of input/output, data, and network)
System environment (constrains, or conditions, affecting the system)
Implementation requirements (start up process, initial data entry, training requirement and software test)
Time and cost estimates
Appendices provide supplemental material

58. Systems Design Completion
User Approval
Users must review and approve the interface design, report and menu designs, data entry screens, source documents, and other areas of the system that affect them
When the system design specification is complete, you distribute the document to a target group of users, IT department personnel, and company management

59. Systems Design Completion
Presentations
The presentations give you an opportunity to explain the system, answer questions, consider comments, and secure final approval
The first presentation is to the systems analysts, programmers, and technical support staff members
Your next presentation is to department managers and users from departments affected by the system

60. Systems Design Completion
Presentations
The final presentation is for company management
Key objective: to obtain management’s approval and support for the next development step
Management might reach one of three decisions: proceed with systems development, perform additional work on the systems design phase, or terminate the project

61. Chapter Summary
An information system combines hardware, software, data, procedures, and people into a system architecture
The analyst must consider enterprise resource planning, initial cost and TCO, scalability, Web integration, legacy interface requirements, security, and processing options
System security is an important concern
An architecture requires servers and clients 49

62. Chapter Summary
Compared to file server designs, client/server systems are more scalable and flexible
In implementing a design, an analyst should consider e-commerce strategies, the availability of packaged solutions, and corporate portals, which are entrances to a multifunction Web site
The primary processing methods are online and batch processing 49

63. Chapter Summary
Networks allow the sharing of hardware, software, and data resources in order to reduce expenses and provide more capability to users
The way a network is configured is called the network topology
The system design specification presents the complete systems design for an information system
Chapter 9 complete 49