Download Information Systems

Information Systems
Gavin Crosthwaite
3 hours = 180 minutes
200 marks
10 short answer
8 extended answer
Various topics
Information Systems
Databases
Computer Architecture
Information Systems
Datum/Data
raw
unprocessed
not useful/lacks meaning
Information
transformed
processed
useful
Data
Information
Knowledge
System
Information Systems
set of related components that process input
data into output data that is organised,
meaningful and useful
Communication System
set of related components that allows a data
transmission, for instance a communication
system in a computer allows it to transfer data to
other computer
An information system deals with data process,
whereas a communication system is a system
that controls the transmission of data
Computer systems
Computer systems that are Computer based information Information systems that are
not information systems
systems
not computer based
Information systems
Management information system
generates timely, accurate information
helps make decisions
Evolve from TPS
Transaction Processing Systems
captures and processes data from day to day
activities
batch processing
collect over time & process all transactions
later
most today are online
Computer Based Systems
any information system which involves a
computer
Carriers
companies that offer telecommunications
between 2 points across the world
Telstra
iinet
Service Providers
Provides a service to customers but doesn’t own
the infrastructure
AAPT
westnet
System Development Life Cycle (SDLC)
1. Preliminary Investigation
Feasibility Study
technical
legal
operational
Measure of
how suitable
system
development
will be to the
company
economical
security
Operational
how well does it work?
will they like it?
will it meet user requirements?
Schedule
deadlines for project
is it reasonable?
Technical
Hardware?
software?
people?
Economic
are the costs worth the benefits?
Tools?
ROI (return on investment)?
cost/benefit analysis?
Legal
Issues such as govt. regulations?
community concerns?
2. Analysis
data gathering techniques?
Observation?
Interview?
Survey?
Questionnaire?
context diagrams
data flow diagram (DFD)
packaged vs. custom software?
convey all solutions?
Select one
find errors early
3. Design
identify technical specs
Hardware?
Software?
ERD (Entity Relationship Diagram)?
Prototyping
Establish an
outline
specification
Develop a
prototype
Evaluate
Specify
Design and
implement
system
mock up of final design
user feedback
outputs from system
GUI (graphic user interface)
CASE tools
designed to assist in one or more activities
in SDLC
Data dictionary
4. Development
write programs
test modules
Unit Test
Systems test
Verifies each
individual program
works by itself
Verifies all programs
in application work
together
Integration Test
Acceptance Test
Verifies application
works with other
applications
Verifies the new
system works with
actual data
finalise program
5. Implementation
test the system in real life
Documentation?
help manual?
train users?
conversion of files to new system?
pilot
direct
parallel
phased
Pilot start with small group of users and gradually add
more users
Phased –
implement the new system in phases
Parallel –
use both systems simultaneously
Direct –
out with the old and in with the new
Maintenance
Represents 66% of the cost of the project
perfective
implies that while it runs smoothly there is still
room for improvement
adaptive
all systems will need to adapt to changing needs
within a company
corrective
problems frequently come up after a period of
time, no matter how thoroughly it has been
tested
help desk?
Context Diagrams
boundary system?
external entity?
data flow?
Data Flow Diagram
Entities?
Files?
Vectors?
Processes?
ENTITIES
square
outside boundary system
must go through a process
FILE
open ended rectangle
what documents are we storing
must go through a process
VECTOR
what information is moving?
be specific!!
PROCESS
MUST be numbered!!
MUST begin with a verb!!
Information MUST be processed or
changed!!
Top-Down
general design & moves to a more detailed
design
Bottom-Up
Individual parts are specified in great detail first
& then linked to form bigger system
Closed Systems
no matter transferred across system
boundary
limited to authorised use
early Mac computers
can’t modify its operations (ATM)
Open Systems
data moves across boundaries
can modify operations
PC as an example
unauthorised exchange of information
allowed
internet
Centralised Systems
information is processed in one location
all processing, software & hardware in one
location as well
Distributed Systems
data processed without necessarily being
connected to a central computer
although distributed, information is transferred
to a central computer
Project Management
Time management
Gantt chart
progress reports?
team planning?
work assignment?
Databases
DBMS (Database Management Systems)
programs that allow a user to create a
computerised database
Definition
collection of data organised in a manner
that allows access for retrieval, and use of
that data
What are the qualities of valuable information?
Accurate
Verifiable
Timely
Organized
Accessible
Useful
Cost-effective
Types
Flat File
Single table
spreadsheet like
lots of repeating data
Incorrect spelling of data
Relational Database
series of tables called relations
joined by keys
most commonly used
queries used to retrieve data entered
relation
a set of tuples that have the same attributes
a table
atomic
single entry per cell
tuple
represents an object or information about that
object
a row
attribute
single piece of data shown in a column
used by developers to refer to a field
how does it fit together
little scope for query optimisation
Index
improves speed of queries in a database
Random
use labels or indexes to get to correct record
eg: if name is Jefferson, go to J, then Je in the
phone book first rather than each name in the
book beginning with ‘A’
Sequential
look at every record in order
very inefficient
humans wouldn’t do it, but computers have
to be told
use random first, then sequential
Data Dictionary
An element that contains data about each
file in a database and each field in the
database
Keys
Primary
attribute in a database that uniquely
identifies each tuple in a file
Foreign
a key from another table that is used to
define a relationship to another record in
another table
has the same name and properties as the
primary key from which it is copied
Normalisation
st
1 Normal Form (1NF)
There are no repeating groups
All the key attributes are defined
All attributes are dependent on the primary
key
nd
2 Normal Form (2NF)
st
Its in 1 Normal Form
It includes no partial dependencies (where an
attribute is dependent on only part of a primary
key)
rd
3 Normal Form (3NF)
nd
Its in 2 normal form
It has no transitive dependencies (where a nonkey attribute is dependent on another non-key
attribute)
Entity Relationship (ER) Diagram
Entity
Relationship
SQL Queries
Know how to create them!!
Computer Architecture
Central Processing Unit (CPU)
control unit
registers
arithmetic logic unit (ALU)
Buses
Peripheral Component Interconnect (PCI)
A standard describing how the peripheral
components of a computer system may be
connected together
Universal Serial Bus (USB)
a protocol for transferring data to and from
digital devices
NuBus
interface used in Macintosh computers to
transfer video data from memory to the graphics
display card
Small Computer System Interface (SCSI)
interface that serves as an expansion bus that
can be used to connect hard disk drives, tape
drives, and other hardware components
Random Access Memory (RAM)
memory that allows any storage location to be
accessed randomly
Read Only Memory (ROM)
memory whose contents can be accessed
and read but cannot be changed
Cache
block of high speed memory where data is
copied when it is retrieved from the RAM
located on CPU
level 2
Also located on CPU
level 3
Reduced Instruction Set Computing (RISC)
small number of assembly instructions
each of which performs simple operations
Complex Instruction Set Computing (CISC)
large number of often complex assembly
instructions
more than one complex
Fetch-Execute Cycle
1) Fetch
2) Decode
3) Execute
4) Store
What is a fetch-execute/machine cycle?

Four operations of the CPU comprise a machine cycle
Step 1. Fetch
Obtain program instruction
or data item from memory
Memory
Step 2.
Decode
Step 4. Store
Translate
instruction into
commands
Write result to memory
Processor
ALU
Step 3. Execute
Carry out command
Control Unit
Storage
Hard Drive?
Compact Disc (CD)?
Digital Versatile Disc (DVD)?
Flash Drive (USB)?
Open System Design
Standards Compliance
Firmware
instructions and data programmed into the
circuits responsible for controlling the
operation of peripheral devices
Software
system software
operating systems
application software
office suites
Sequential Processing
all processing on a single processor
computer
Parallel Processing
to process data more quickly, more
processors can be added to the system
Distributed Processing
Troubleshooting
Preventative Maintenance
1) Defragmentation
2) Clear temporary files
3) Back up
Full back up
all files are saved
time consuming
Differential back up
requires minimal space
long recovery time
Incremental back up
Only recent changes saved
even longer recovery time