What is System Design?
• In System design, we use the requirements we
developed in system analysis to create a
blueprint of the future system
• Successful design builds on what we have
learned in analysis and transforms that
knowledge into a working system.
• Design is still planning as the system need not
be developed during this phase.
Design Strategies
• Custom development (build from scratch)
• Purchase and customize
• Outsource development
Custom Development
• PROS
– Allows flexibility and
creativity
– Builds technical skills and
functional knowledge inhouse
– Best ‘fit’
• CONS
– Requires significant time and
effort
– May exacerbate existing
backlogs
– May require missing skills
– Often costs more
– Often takes more time
– Risk of project failure
Packaged Software
• Include small single-function tools
• All-encompassing enterprise resource planning (ERP)
systems
• Rarely a perfect fit with business needs
• May allow for customization
– Manipulation of system parameters
– Changing way features work
– Synchronizing with other application interfaces
Outsourcing
• Hiring an external vendor, developer, or
service provider
• May reduce costs or add value
• Risks include possibly
–
–
–
–
Losing confidential information
Losing control over future development
Losing control over future cost structure
Losing learning opportunities
Outsourcing Contracts
• There are Three types:
• Time and Arrangement:
– Pay for what is needed to get job done. Flexible but risk of
large bill at the end.
• Fixed-price
– Certainty regarding payment but very little flexibility in
delivering IS support. ‘You get what you ask for.’
• Value-added
– Outsourcer shares in benefits gained from the system.
Selecting a Design Strategy
• Consider each of the following:
– Business need
– In-house experience
– Project skills
– Project management
– Time frame
Key Definitions
• The architecture design consists of plans for the
hardware, software, communications, security ,
and global support for the new application
• The 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).
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.
Architectures
• Server based
• Client based
• Client-server based
– thick versus thin client
– cloud computing
Server-Based Computing
(and, essentially, Thin-Client Computing)
Client-Based Computing
Client-Server-Based Computing
Client-Server Attributes
• Typical Pros
– Compatible with webbased system design
– Scaleable
– Work with multiple
vendors/products
– No central point of
failure
• Typical Cons/Limits
– Complexity
– New programming
languages and
techniques (stress for
personnel)
– More complex to update
Identifying Threats to the System
• A threat is any potential adverse occurrence that can
do harm to the application or its data
• Threats come from internal as well as external
sources
• Categories of threats
– Disruptions, destruction and disaster
• Viruses fall into this category
– Unauthorized access
Most Common Threats
Creating Controls
• A control is something that mitigates or stops
a threat
• Controls include
– redundancy
– fault tolerant servers
– disaster recovery plans
– anti-virus software
Additional Controls Include
• A security policy
• ‘Social Engineering’
• Passwords and encryption
– What you have
– What you know
– What you are
• Firewalls
– wired, wireless controls
Current Threats
• Malware Delivery
– Software Updates
– Banner Ads (‘malvertising’)
– Downloadable documents
– Man-in-the-middle
– Keyloggers
The threat of open WiFi
• ‘Sidejacking’
– packet sniffers intercept traffic between two html
parties and steal the session cookie
– Firesheep is an application that supports this as an
extension of the Firefox browser
• requires Firefox browser use
• cannot read https sessions