ITEC 3010 Systems Analysis and Design, I

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ITEC 3010 Systems Analysis and Design,
I LECTURE 8-2 Elements of Systems Design
Prof. Peter Khaiter
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Topics

• Elements of Design
• Inputs for System Design
• Design and Integrate the Network
• Design the Application Architecture
• Design the User Interfaces
• Design the System Interfaces
• Prototype for Design Details
• Deployment Environment
• Software Application Functions
• Internet and Web-Based Application Architecture
• Middleware

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Elements of Design

• Design is process of describing, organizing, and
  structuring system components at architectural
  design level and detailed design level
• Focused on preparing for construction
• Like developing blueprints
• Three questions
• What components require systems design?
• What are inputs to and outputs of design process?
• How is systems design done?

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Components Requiring Systems Design
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Inputs for System Design

• Design
• Converts functional models from analysis into
  models that represent the solution
• Focused on technical issues
• Requires less user involvement than analysis
• Design may use structured or OO approaches
• Database can be relational, OO, or hybrid
• User interface issues

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Analysis versus Design
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Traditional Structured and Object-Oriented Models
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SDLC Phases with Design Phase Activities
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Design Phase Activities and Key Questions
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Design and Integrate the Network

• Network specialists establish network based on
  strategic plan
• Project team typically integrates system into
  existing network
• Technical requirements have to do with
  communication via networks
• Technical issues handled by network specialists
• Reliability, security, throughput,
  synchronization

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Design the Application Architecture and Software

• Specify how system use cases are carried out
• Described during system analysis as logical
  models of system activities
• After design alternative is selected, detailed
  computer processing is designed as physical
  models
• Approach varies depending on development and
  deployment environments

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Design the User Interfaces

• User interface quality is critical aspect of
  system
• Design of user interface defines how user
  interacts with system
• GUI windows, dialog boxes, mouse interaction
• Sound, video, voice commands
• To user of system, user interface is the system
• User interface specialists interface designers,
  usability consultants, human factors engineers

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Design the System Interfaces

• System interfaces enable systems to share and
  exchange information
• Internal organization systems
• Interfaces with systems outside organization
• New system interfaces with package application
  that organization has purchased and installed
• System interfaces can be complex
• Organization needs very specialized technical
  skills to work on these interfaces

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Design and Integrate the Database

• System analysis data model used to create
  physical database model
• Collection of traditional computer files,
  relational databases, and/or object-oriented
  databases
• Technical requirements, such as response times,
  determine database performance needs
• Design work might involve
• Performance tuning
• Integration between new and existing databases

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Prototype for Design Details

• Continue to create and evaluate prototypes during
  design phase
• Prototypes confirm design choices
• Database
• Network architecture
• Controls
• Programming environment
• Rapid application development (RAD) design
  prototypes evolve into finished system

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Design and Integrate the System Controls

• Final design activity to ensure system has
  adequate safeguards (system controls) to protect
  organizational assets
• Controls are needed for all other design
  activities
• User interface limit access to authorized users
• System interface protect from other systems
• Application architecture record transactions
• Database protect from software/hardware failure
• Network design protect communications

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Network Design

• Integrate network needs of new system into
  existing network infrastructure
• Describe processing activity and network
  connectivity at each system location
• Describe communications protocols and middleware
  that connects layers
• Ensure that network capacity is sufficient
• Data size per access type and average
• Peak number of access per minute or hour

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Computer Networks

• Set of transmission lines, specialized hardware,
  and communication protocols
• Enables communication among different users and
  computer systems
• Local area network (LAN) less than one kilometer
  long connects computers within single building
• Wide area network (WAN) over one kilometer long
  implies much greater, global, distances
• Router directs information within network

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A Possible Network Configuration for RMO
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The Internet, Intranets, and Extranets

• Internet global collection of networks that use
  TCP/IP networking protocols
• Intranets
• Private networks using same TCP/IP protocols as
  the Internet
• Limited to internal users
• Extranets
• Intranets that have been extended outside the
  organization

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Network Diagram for RMO Customer Support System
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Deployment Environment

• Deployment environment definition bridges
  analysis and design
• Hardware
• System software
• Networking
• Common deployment environments in which system
  will operate
• Related design patterns and architectures for
  application software

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Application Architecture

• Complex hardware/networks require more complex
  software architectures
• There are commonly used approaches (patterns)
  for application architecture
• Client/server architecture
• Three-layer client/server architecture
• Web services architecture
• Internet and Web-based application architecture

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Software Application Functions

• Presentation logic (i.e. HCI)
• Application logic (i.e. the processing of
  business rules processing)
• Data access logic (i.e. the processing required
  to access data database queries in SQL)
• Data storage (i.e. data files)
• There are several alternatives for the processing
  environment
• Centralized systems
• Distributed computing

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Centralized systems

• Prior to the early 1970s there was only one
  technological environment the mainframe
  computer system at a central location
• The only options focused around kinds of
  input/output (e.g., keypunch, key-to-tape, or
  interactive input using video display terminal)
  and whether input/output devices would be placed
  in remote locations
• Although they are no longer the preferred
  platform for deploying ISs, they are still widely
  used as a subsystem of a larger, sometimes
  distributed information system or for large-scale
  batch processing applications (e.g., banking,
  insurance, government, etc.) where
• Some input transactions dont need to be
  processed in real time
• On-line data-entry personnel can be centrally
  located
• Large numbers of periodic outputs are produced by
  the system
• There are three types of centralized systems
  single, clustered and multicomputer architectures

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Single Computer Architecture
Places all information system resources on a
single computer system and its directly attached
peripheral devices Users interact with the
system via simple input/output devices directly
connected to the computer Requires all users be
located near the computer All 4 software
application functions are realized on a mainframe
computer (server host) server-based
architecture Advantage Simplicity of
maintenance relatively easy to design, build and
operate Disadvantage The capacity limits make
single computer impractical or unusable for large
ISs cannot provide all the required processing,
data storage, and data retrieval tasks. However,
many systems require more computing power than
one single machine can provide (a clustered or
multicomputer architecture is required)
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Single-Computer, Clustered, and Multicomputer
Architectures
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Server-based Architecture
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Clustered Architecture

• Clustered architecture is a group (or cluster)
  of computers of the same type that have the same
  operating environment and share resources
• Computers from the same manufacturer and model
  family are networked together
• Application programs may be executed on any
  machine in the cluster without modification due
  to similar hardware and operating systems
• Cluster acts like a single large computer
  system (program movement and access to resources
  on other machines occur quickly and efficiently
  due to rapid and direct communication at the
  operating system level)
• Often one computer may act as entry point and
  the others function as slave computers

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Multicomputer Architecture
Multicomputer architecture is a group of
dissimilar computers that are linked together but
the hardware and operating systems are not
required to be a similar as in the clustered
architecture Hardware and software differences
do not allow movement of application programs
between computers (instead, resources are
exclusively assigned to each computer system)
System still functions like one single large
computer Can have central computer and slave
computers Main computer may execute
programs and hold database The front-end
computer may handle all communication lines with
other computers or simple terminals Notes on
Centralized Systems Clustered architectures may
be cost efficient and provide greater total
capacity if similar operating system and hardware
are used Multicomputer architectures are good
when the centralized system can be decomposed
into relatively independent subsystems (each
possibly with its own operating system and/or
hardware platform)
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Distributed Architecture

• Distributes system across several computers and
  locations distributed computing
• Relies on communication networks for geographic
  connectivity
• Client/server architecture dominant model for
  distributed computing

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Client/Server Architecture

• The dominant architectural model for distributing
  information resources
• Two-tire architecture divides the information
  system processes into two classes
• Server manages system resources and
  provides access to those resources and services
  to other computers on the network
• Client computer uses communication
  interface to requests services from other
  computers on the network
• Computer software that implements communication
  protocols on the network is called middleware
• Advantage deployment flexibility
• Location, scalability, maintainability
• Disadvantage complexity
• Performance, security, and reliability

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Interaction Among Multiple Clients and a Single
Server
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Client/Server Architecture shared printer
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Fat Client Architecture
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Fat Server Architecture
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Three-Layer Client/Server Architecture

• The data layer is a layer on a client-server
  configuration that manages stored data
  implemented as one or more databases
• The business logic layer contains the programs
  that implement the rules and procedures of
  business processing (or program logic of the
  application)
• The view layer contains the user interface and
  other components to access the system (accepts
  user input, and formats and displays processing
  results)
• This approach is called tree-layer architecture
• The IS divided into three layer is relatively
  easy to distribute and replicate across a network
  (interactions among the layers are always have a
  form of either request or response)
• It makes the layer relatively independent of one
  another, thus they can be placed on different
  computer systems with network connections and
  middleware serving

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Three-Layer Architecture
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Three-Layer Architecture Software Application
Functions
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N-Layer Client/Server Architecture
When processing requirements or data resources
are complex, three-layer architecture can be
expanded into a larger number of layers (n-layer
or n-tiered architecture) Next slide shows an
example in which the data layer is split into two
separate layers the combined database server and
servers that control the individual databases
(marketing, production, accounting). The
business logic layer interacts with a combined
database server that provides a unified view of
the data stored in several different databases.
The responses from the individual database
servers are then combined to create a single
response to send to the business logic layer.
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N-Layer Architecture
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Four-Tier Architecture
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Internet and Web-Based Application Architecture

• Web is complex example of client/server
  architecture
• Can use Web protocols and browsers as application
  interfaces
• Benefits
• Accessibility
• Low-cost communication
• Widely implemented standards

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Negative Aspects of Internet Application Delivery

• Breaches of security
• Fluctuating reliability of network throughput
• Throughput can be limited
• Volatile, changing standards

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Web Services Architecture

• A client/server architecture
• Packages software functionality into server
  processes (services)?
• Makes services available to applications via Web
  protocols
• Web services are available to internal and
  external applications
• Developers can assemble an application using
  existing Web services

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Web Services Architecture (continued)
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Middleware

• Aspect of distributed computing
• Connects parts of an application and enables
  requests and data to pass between them
• Transaction process monitors, object request
  brokers (ORBs), Web services directories
• Designers reply on standard frameworks and
  protocols incorporated into middleware

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Readings
Todays lecture Chapter 9 Elements of Systems
Design For next lecture Chapter 11
Object-Oriented Design
Thank you !!!