Transcript SYS364 - Seneca - School of Information & Communications

SYS364
Architecture
Today’s Agenda
 System Architecture
 Processing Methods
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On-line, Batch
Centralized, De-centralized
 Networking
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LAN/WAN/MAN
Client/Server, File/Server
System Architecture
 Refers to the Logical design and
physical structure of a system
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Includes hardware, software, design and
processing methods
 Environment & Platform
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Server Farm with UNIX(s) + Apache
AS/400 with Websphere + NT partitions
Processing Methods
 Environment and/or Platform refer to a
specific combination of hardware and
software
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Influences system architecture
Reinforces bias (when all you’ve got is a
hammer, everything looks like a nail)
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Becomes religious (but there is no “one
true” platform)
…just a few years ago
 Two predominant environments
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Mainframes with terminal access
Stand alone PC’s running one program at a
time
Today
 The Internet connects everything
 Businesses are more dynamic than ever
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Competitive pressure: e-commerce, 24/7
Corporate “right sizing”
Mergers
 Employees at all levels satisfy their own
information needs – IT provides users with
the technology, tools and resources
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Requires that systems be cost effective, flexible
and user-friendly
Impact on Analyst’s strategy
 Business operational requirements
 Match software to business process
 Level of integration with outside systems
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EDI, XML, information/transaction exchange
 Level of access for customers and
suppliers into your platform
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Internet, telephony, call centers
On-line Data Processing
 Transactions are processed completely when
and where they occur
 Users interact directly with the information
system programs (not forms)
 Programs update DB directly & immediately
(input verification is critical to system integrity)
 system availability is crucial
 Consider cost of downtime, manual backup
procedures
Batch Data Processing
 Data is collected and processed in
batches, logically and physically.
 Data captured, then entered,
then input.
 May be more efficient than on-line
 Typically used for large amounts of data
that must be processed on a routine
schedule
 What in case study is batch?
Batch Data Processing
 Transactions are collected and
processed periodically
 Computer operators can run batch
programs on a pre-determined schedule
without user involvement
 Payroll, Accounting close off
 Data Warehouse, EIS, DSS updates
 EDI
Level of Automation
 Volume: How much info is there?
 Volatility: How often does info change?
 Timeliness: When does matter?
 Forms and batch processing
 PDA & handheld data collection devices
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With wireless modems
 Online screens everywhere
Centralized Systems
 Server or Host
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Mainframe and terminals
 e.g. IBM “big iron”, AS/400 and large UNIX
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In the past, slow + $$$ communications
networks limited remote data entry/input
 Clustered systems
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Many identical systems with load
balancing, fail-over. e.g. Server farms.
A horror when it’s time to upgrade/update.
 Heterogeneous environments
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Variety of platforms, use middleware
Distributed Systems
 For business, computing is distributed
geographically, connected by networks
 Local and regional tasks are performed
by decentralized computers
 Summary uploads to central office
 May use Client/Server model
Distributed Systems Design
 processing involves local and central data
 Data may be stored closer to users and
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reduce network traffic
Easily scalable – new storage sites can be
added without affecting network operation
Less likely to experience a catastrophic failure
…what about security?
…network management?
Database replication and synchronization
issues
Distributed Processing Today
 Distributed CPUs
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SETI@Home
DistributedScience
Entropia
 Distributed Storage (Peer-to-Peer)
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Napster
Gnutella
Networks and the Net
 The value of a network is the square of
the number of things connected to it. —
Metcalfe's law for Bob Metcalfe, the
inventor of Ethernet and 3COM.
 The value of the Net is the number of
groups people on the network can form.
Reid’s Law
Moore's Law=
processing
power doubles
every 12-18
months
n = people
2
3
4
5
6
10
100
1,000
10,000
100,000
1,000,000
10,000,000
100,000,000
1,000,000,000
Metcalfe's Law = the value
of n items in a network is
proportional to n^2. I.e. the
number of one-to-one
connections.
n(2)-n = connections
2
6
12
20
30
90
9,900
999,000
99,990,000
9,999,900,000
999,999,000,000
99,999,990,000,000
9,999,999,900,000,000
999,999,999,000,000,000
Reed's Law: Net's value comes
from its enabling of groups, I.e.
the number of distinct subgroups
that can form in a set of N
members is 2^N
2(n)-n-1 = groups
1
4
11
26
57
1,013
1,267,650,600,228,230,000,000,000,000,000
1.072E+301
#NUM!
#NUM!
#NUM!
#NUM!
#NUM!
#NUM!
The Net
 Intranet, extranet, internet
 Accessibility – browsers make presentation
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layer independent of the platform’s
software/hardware/operating systems
Low cost communications
Widely implement standards (HTML, XML)
Security slowly getting better
Reliability – no guarantees yet
Throughput – last mile problem
Volatile standards and tools
Local Area Networks (LANs)/
Wide Area Networks (WANs)
 LANs
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Hardwire a group of PCs together in a limited area
to a server
 WANs
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Uses a combination of phone lines, fiber optic
cables, microwave transmission and satellites to
connect PCs and LANs into a network that can
span the globe
X25, Frame Relay, ATM (Asynch Xfer Mode)
Internet built on TCP/IP
 MANs (Metropolitan Area Networks)
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New Ethernet wireless standard
Network Issues
 Software licensing
 Traffic and Bandwidth
 Security and Firewalls
 Topology, Configuration, Protocol
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These issues need an expert
(I.e. your friends in CNS program)
Client/Server Systems
 Divides processing between one or more
clients and a central server
 A client handles the user interface
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Data entry
Editing
Data query
 A server handles
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Data access
Processing
Database management functions
Benefits of Client/Server
 ? Easily scalable (up or down) to meet
changing business needs ?
 ? Transfer of expensive mainframe
systems to less expensive clients ?
 In practice, benefits are dubious
and many C/S projects failed
 Is a browser on the Web closer to
Client/Server or Mainframe/Terminal?
Systems Design Completion
 System Design Specification
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Created before the next SDLC Phase,
Implementation
 Detailed costs
 Staffing
 Scheduling
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Oriented to Programmers so they know
what to do
Oriented to Users so they know what they
are getting
Approvals of the Systems
Design Specification
 Users approve all report and output
screen designs, menu and data entry
screens, source documents
 IS Management will approve staffing,
costs, hardware and software and
effects on the operating environment
 Other management – does the new
system meet business objectives?
Technical and Management
Presentations
 Programmers/operators/IS staff
 IS Management
 Company management
 Possible outcomes
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Proceed with development
Perform additional work on the design phase
Terminate the project
Summary
 Architecture
 Processing
 Networking
 Completing the Design Phase of the
SDLC