Chapter 7 – System Architecture Flashcards
System architecture
• Translate the logical design of an information system into a physical structure that includes:
- Hardware
- Software
- Network support
- Processing methods
• Objective of architecture design:
- Determine how the software components of the information system will be assigned to the hardware devices of the system
System Architecture Checklist (*)
7 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 (LSI)
• Processing options
• System security
Enterprise Resource Planning (ERP)
• Objective: - Establish a company-wide strategy for using IT resources • Describes environment – Platform - Hardware & software - Advantages • Supply chain management - Supplying materials, information from the suppliers ~ To the manufacturer ~ To the wholesaler ~ To the retailer ~ To the consumer - From raw material to the consumer
Initial Cost and TCO
• Main components: - Initial Cost ~ Physical purchases, fees, and other costs - TCO: ~ Soft costs: \+ Support \+ Training \+ Downtime • Make decisions that will have a major impact on: - Initial costs and TCO ~ For the new system - Review all previous cost estimates - Ask questions: ~ Choices \+ Development alternatives \+ Packages ~ Availability of new types of outsourcing - Answers may affect the initial cost and TCO for the proposed system
Scalability
• Refers to a system’s ability to:
- Expand easily
- Change easily
- 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
• Example:
- Physical system
- Database
~ Adding new nodes, business parts, new trucks, routes, etc.
- Scalable network could handle anywhere from a few dozen nodes to thousands of notes
Web integration
• Includes: - Applications • Web-centric architecture • Avoids many of: - Connectivity problems - Compatibility problems ~ That typically arises • E-marketplaces
Legacy System Interface Requirements
• Legacy System: - Traditional but powerful & useful • New system might have to interface with: - One or more legacy systems • New system interfacing with legacy systems involves: - Analysis of data formats - Analysis of compatibility • Analyst: - Must know if the new application: ~ Will replace the legacy system
Processing Options
• Planning the architecture: - Designers must consider how the system will process data - online or in batches • Provision: - Must be made for: ~ Backup ~ Speedy recovery \+ In the event of system failure • Example: - High capacity transaction such as daily order entry system requires more network, processing and data storage resources than a monthly billing system that handles data in batches
Security Issues
• A concern at every stage of system development
• System analyst must consider security issues that relate to:
- System design specifications
- Determine how the company will address them
• Web-based systems:
- Introduces additional security concerns
Planning the Architecture
• Every information system involves 3 main functions: - Data storage & access methods - Application problems ~ To handle the processing logic - An interface ~ That allows users to interact with the system • Functions: - Performed on: ~ A server ~ A client ~ Divided between the server and the client • Servers (*) - Server ~ A computer that supplies: \+ Data \+ Processing services \+ Other support - To one or more computers called clients - Clients - Maintenance architecture ~ Describes a multiuser environment where the server is significantly more powerful than the clients
Client/Server Architecture (*)
• Client/server architecture - The client handles the entire user interface including: ~ Data entry ~ Data query ~ Screen presentation logic
• Client:
- Submits a request for information from the server
~ Which carries out the operation and responds to the client
• Legacy data:
- Installed base of mainframe data - Difficult to access and transport to a client/server environment
Fat client / Thick client
• Design locates all or most of the application processing at:
- The client
• Provide better performance because:
- Program resides on the server near the data
Thin client
• Design locates all or most of the processing logic at:
- The server
• Handles more of the processing
• Must access and update the data more often
Client/Server Tiers (*)
• Two-tier designs
- Server & client
- User interface resides on the client
- All data resides on the server
- Application logic can run either on the server and client
or
- Shared between the client & the server
• Three-tier design
- Data server, application & client
- Middle layer between the client and server
- Server:
~ Processes the client requests
+ Translates them into data access commands that can be carried out by the server
Middleware (*)
• Software that enables the tiers to: - Communicate - Pass data back and forth • Ease the task of: - Designing - Programming - Managing ~ Distributed applications by providing a \+ simple, consistent, integrated distributed programming environment.
