cse1204 - information systems 1 ims1001 - information systems 1 revision
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CSE1204 - Information Systems 1 IMS1001 - Information Systems 1
Revision
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Subject Overview System concepts and information systems Systems development and the SDLC Information gathering techniques Modelling Process modelling using DFDs Data Dictionary: minispecs, detailed
process description
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Subject Overview System design principles – structured design Communicating using documentation and
presentations Working in teams Ethics and professional practice People and their roles in the SDLC Project management Quality - product and process Types of information systems
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System concepts and information systemsA system: An inter-related set of components that
interact to accomplish goals system elements
• a boundary, a purpose, an environment, interfaces, input, processing, output, feedback, constraints
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Information systems An Information System is a formal
arrangement of people, data, processes integrated to help manage complex business functions and to support and improve business operations, as well as supporting the problem-solving and decision-making activities of managers.
It transforms Data into Information
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data input - recording information data storage/retrieval - keeping information data processing - transforming information data output - displaying/presenting information
Information System major functions
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Benefits of an Information System
the right information to the right degree of accuracy when it is required in the right format/layout to the right people in the most efficient way possible
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Computerised information systems
human v. computer – strengths and weaknesses
IS:• tireless• mundane, repetitive• constant level of quality• meticulous
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Systems development and the SDLC The need to build new information systems or
change existing ones comes about because:• there are problems in the way in which
existing systems operate; or• changes in circumstances create
opportunities to improve things by doing them differently; or
• there are complex requirements or pressures e.g. co-ordinating other processes, new government legislation
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The Systems Development Life CycleThe SDLC provides: a systematic and orderly approach to solving business
problems a means of managing, directing, monitoring and
controlling the process of system building, including:
• a description of the process - steps to be followed
• deliverables - reports/programs/documentation/etc
• milestones - dates of completion of steps or deliverables
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Systems Development Phases
Analysis
Design
Implementation
Review
Maintenance
Quality
Documentation
Ethics
Project Management
Analysts RoleInitiation
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SDLC phases activities in each phase output from phases
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Systems DevelopmentActivities involved in building computer-
based information systems are:- identifying problems analysing and describing information and
processing needs designing solutions to meet those needs acquiring/building new systems implementing new systems maintaining information systems
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Data GatheringThe data gathered should include: system description - how things work or should
work system problems - what is wrong or needs
improvement opportunities - identifying scope for innovation
or new ways of doing things
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Data gathering techniques
Interviews
Questionnaires
Observation
Reports
System Documentation
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Modelling Why do we do it?
• Communication with ourselves
• Communication with others
How do we do it?• informal techniques
• formal techniques
How effective is it?• different techniques for different purposes
• eg. a road map, an organisation chart, a data flow diagram
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Process modelling processes are the “action” part of
businesses principal techniques
• functional decomposition• data flow diagrams
associated techniques for modelling the details of low-level processes• structured English• decision tables and decision trees
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Data flow diagrams (DFDs) model the flow of data into, through, and
out of an information system represent an information system as a
network of communicating processes• show the processes that change or transform
data• show the movement of data between
processes
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2.0
calculateprice
loan application
Products
Suppliers
• process
• data flow
• data store
• source/sink
Components of data flow diagrams
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any "real" system is too large to represent as a single data flow diagram
the solution is to decompose the system into a hierarchy of levels of processing
the process model of the system then consists of a set of levelled data flow diagrams
balancing DFDs
Levelling Data Flow Diagrams
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Levelling DFDs
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3
1.1
1.2
Context diagram
Level zero diagram
Diagram 1 (at level 1)
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the data dictionary is a database or repository of information about objects identified during systems development
every object (and each of its components) must have a definition in the data dictionary
the data dictionary is a major source of documentation about the information system
Data Dictionary
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the processing that occurs within the bottom level (primitive) processes in DFDs needs to be defined
detailed process descriptions are also known as minispecs
detailed process descriptions form part of the data dictionary: they define the contents of primitive processese.g. Structured English, decision tables, decision trees
Detailed Process Definitions
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System designThe main objectives of the design phase are: to provide alternative design solutions to assist in the selection of a design solution to acquire the necessary hardware and software to design and integrate the various physical
system components .. interfaces, security controls, files/databases, etc ...
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Structured design principles
Design features that lead to more correct systems that are easier to maintain and modify: • Small module .. easier to write and test, and they are
less likely to affected by change• Modular independence (coupling) .. the less one module
depends upon another, the easier it will be to test and maintain
• Modular strength (cohesion) .. the less unnecessary/ extraneous elements the module contains the better it will perform
• “black box” characteristics
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Documentation• Reduces the need to refer problems to the system developer
once the system is installed• Product and documentation should be developed at the same
time• Documentation is communication:• typical documents in IS development:
• Data manual • System Manual • User manual • Operation manual
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Presentations person to person communication high credibility relatively short duration no permanent record
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Using presentations in systems development reporting an important event or milestone sharing knowledge with your peers responding to a request for information gaining immediate feedback on a proposal requesting approval influencing the audience demonstrating an operational feature
• person to person communication• high credibility• relatively short duration• no permanent record
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systems development is a team effort good teams:
• diversity• communication• trust• putting the team first
Teams in systems development
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Project manager Analysts/designers Programmers/database/network designers Senior managers /Middle managers End users (operational staff) - who do the work Owners and users are primary source of needs,
requirements Owners and users are critical to system
acceptance and use
People in the SDLC
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The Role of the Systems Analyst to understand the business’s information needs
• what information is needed?• for whom?• in what form?• when?
to describe the business’s information flows to identify problems and opportunities to suggest possible system solutions
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Project management: why is it needed? the number of people involved the number of tasks to be done the extent of the interaction between the
tasks and people the complexity of the interactions between
the tasks and people
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Basic process of project management
• defining dependencies between tasks
• allocate resources to tasks
• monitor progress against plan
• take remedial action
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Quality in systems development various definitions e.g. the ability to satisfy
stated/implied needs the cost of detecting and correcting errors rises
greatly during the SDLC must be embedded in the systems development
process: product and process standards technical reviews system quality criteria eg. portability, flexibility
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Types of Information Systems There is a range of information systems to serve
the varied needs of users:• Transaction processing systems • Electronic commerce• Process control systems • Management support systems: Management information
systems, Decision support systems, Executive information systems
• Knowledge-based systems: Expert systems, Neural networks, Robotics
• Multimedia systems• Office automation systems • Geographical information systems
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• Operational• Schedule• Technical• economic
Initiation phase Analysis phase Design phase Implimentation Maintenance
Testing feasibility
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intuitive v. scientific problem solving milestones PERT chart v. GANTT chart partitioning deliverables data flows information v. data context diagram
Terms