Transcript Week 8 - CSUSAP

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Systems Analysis and Design in a
Changing World, Fourth Edition
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Learning Objectives
 Discuss
the issues related to managing and
coordinating the design phase of the SDLC
 Explain
the major components and levels of
design
 Describe
each design phase activity
 Describe
common deployment environments and
matching application architectures
 Develop
a simple network diagram and estimate
communication capacity requirements
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Overview
 This
chapter

Completes the transition from analysis to design

Discusses issues related to design of new system

Describes all design phase activities

Describes network and architecture design
 Analysis
focuses on what system should do—
business requirements
 Design
is oriented toward how system will be built
—defining structural components
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Understanding the 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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Analysis Objectives to Design Objectives
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Moving from Analysis to 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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Traditional
Structured and
ObjectOriented
Models
(Figure 9-3)
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SDLC Phases with Design Phase Activities
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Design Phase Activities and Key Questions
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(Figure 9-5)
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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
 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, such as physical data flow diagrams and
structure charts (traditional) or interaction
diagrams and class diagrams (OO)
 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
interface specialists – interface designers,
usability consultants, human factors engineers
 User
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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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Project Management—Coordinating the
Project
 Manage
changing requirements
 Coordinate
design elements
 Coordinate
project teams

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Project schedule - coordinate ongoing work
 Coordinate
information

CASE tools and central repository

Team communication and information coordination

Track open items and unresolved issues
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System Development Information Stored in the
CASE Repository (Figure 9-6)
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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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Single-Computer and Multitier Architecture
 Single-computer
architecture

Mainframe-based

Limited by single machine capacity
 Clustered
and multi-computer architecture

Group of computers to provide processing and
data storage capacity

Cluster acts as a single system

Multicomputer hardware/OS can be less similar
than clustered
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Single-, Clustered, and
Multicomputer Architectures
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Centralized and Distributed Architecture
 Distributes
system across several computers and
locations
 Relies
on communication networks for
geographic connectivity
 Client/server
architecture dominant model for
distributed computing
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Computer Network
 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
– global collection of networks that use
TCP/IP networking protocols
 Internet
 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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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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Client/Server Architecture
 Client/server
divides programs into two types
– manages information system resources
or provides well-defined services for client
 Server
– communicates with server to request
resources or services
 Client
 Advantage

– deployment flexibility
Location, scalability, maintainability
 Disadvantage

– complexity
Performance, security, and reliability
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Interaction Among Multiple Clients and a
Single Server (Figure 9-11)
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Client/Server Architectural Process
 Decompose
application into client and server
programs, modules, or objects

Identify resources or services that can be centrally
managed by independent software units
 Determine
which clients and servers will execute
on which computer systems
 Describe
communication protocols and networks
that connect clients and servers
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Three-Layer Client/Server Architecture
 Layers
can reside on one processor or be
distributed to multiple processors
layer – manages access to stored data in
databases
 Data
logic layer – implements rules and
procedures of business processing
 Business
layer – accepts user input and formats and
displays processing results
 View
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Three-Layer Architecture
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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 (Figure 9-13)
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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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Internet and Web-Based Application
Architecture
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 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
 Throughput
 Volatile,
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reliability of network throughput
can be limited
changing standards
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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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Network Diagram for RMO
Customer Support System (Figure 9-14)
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CD-Selection Example
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Functional Requirements:

1. Place Requests for CDs
1.1 Customers will access the Internet system to look for CDs of interest. Some customers will search for
special CDs or CDs by specific artists, while other customers want to browse for interesting CDs in
certain categories (e.g. rock, jazz, classical).
1.2 When the customer has found a CD he or she wants, the customer will check to see which store(s)
have the CD in stock. They will use zip code to find stores close to their location.
1.3 Customers can immediately place a hold on any CD in stock at any of the stores and then come into
the store and pick it up (see requirement 3 below).
1.4 If the CD is not available in the customer’s preferred store, the customer can request that the CD be
special ordered to that store for later pickup. The customer will be notified by e-mail when the
requested CD arrives at requested store; the CD will be placed on hold (which will expire after 7 days).
This process will work similarly to the current special order system.

2. CD Marketing
2.1 The Internet system provides an additional opportunity to market CDs to current and new customers.
The system will provide a database of marketing materials about selected CDs that will help Web users
learn more about them (e.g., music reviews, links to Web sites, artist information, and sample sound
clips). When information about a CD that has additional marketing information is displayed, a link will
be provided to the additional information.
2.2 Marketing materials will be supplied primarily by vendors and record labels so that we can better
promote their CDs. The Marketing Department will determine what marketing materials will be placed
in the system and will be responsible for adding, changing and deleting the materials.
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CD-Selection Example
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3. Process In-store Holds
3.1 When a CD is available in a store, the system will send
a hold request to the in-store system at the selected
store.
3.2 The in-store system will alter the store staff (through an
audible alarm and a popup message).
3.3 Staff will print a label for the requested CD(s), pull them
from the shelves, attach the label, and place them on the
special order shelf. Just like the special orders, the hold
items will be held for 7 days.
3.4 Once the hold has been placed on the shelf, the staff
will enter a hold confirmation, and the system will do an
inventory adjustment to the main inventory database so
that no other holds are accepted for the item.
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CD-Selection Example: Design

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1. Select design strategy
There are three different approaches that could be considered with the
CD Selections system.

Develop the entire system using development resources from CD
Selections.

Buy a packaged software program.

Hire consulting firm or service provider to create the system.

A custom development project using the company’s standard Web
development tools is the best choice for CD Selections. There is one
part of the project that potentially could be handled using packaged
software: the request-taking portion of the application.

Weighted alternative matrix comparing three different shopping cart
programs:
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CD-Selection Example: Design

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Weighted alternative matrix comparing three different shopping cart
programs:
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CD-Selection Example: Architecture Design 9

Begin with the
high-level
nonfunctional
requirements
developed in
the analysis
phase.
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CD-Selection Example: Architecture Design

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A more detail
selected
nonfunctional
requirements
for CD
Selections.
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CD-Selection Example: Architecture
Design

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A three-tier thin client-server architecture is the best configuration for
the Internet portion of the Internet system.

Customers would use their personal computers running a Web
browser as the client.

A database server would store the Internet system’s databases.

An application server would have Web server software and the
application software to run the system.

The in-store system was currently built using a two-tier client-server
architecture, so the portion of the system responsible for the in-store
holds would conform to that architecture.

A second two-tier client-server system would enable staff in the
Marketing Department to maintain the marketing material information.
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Summary
 Systems
design is process of organizing and
structuring components of system to allow
construction (programming) of new system
 Design
phase of project consists of activities that
relate to design of components of new system

Application architecture, user interfaces, system
interfaces, databases, network diagrams, system
controls

Prototyping may be required to specify any part or
all of the design
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Summary (continued)
 Inputs
to design activities are diagrams built
during analysis
 Outputs
of design are also diagrams that
describe architecture of new system and detailed
logic of programming components
 Inputs,
design activities, and outputs are different
depending on whether a structured approach or
an object-oriented approach is used
 Architectural
design adapts to development
environment and decomposes design into layers
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