CSE1204 - Information Systems 1 IMS1001 - Information Systems 1

Revision

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

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

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

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

data input - recording information data storage/retrieval - keeping information data processing - transforming information data output - displaying/presenting information

Information System major functions

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

Computerised information systems

human v. computer – strengths and weaknesses

IS:• tireless• mundane, repetitive• constant level of quality• meticulous

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

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

SDLC phases activities in each phase output from phases

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

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

Data gathering techniques

Interviews

Questionnaires

Observation

Reports

System Documentation

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

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

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

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)

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

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

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 ...

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

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

Presentations person to person communication high credibility relatively short duration no permanent record

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

systems development is a team effort good teams:

• diversity• communication• trust• putting the team first

Teams in systems development

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

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

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

Basic process of project management

• defining dependencies between tasks

• allocate resources to tasks

• monitor progress against plan

• take remedial action

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

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

• Operational• Schedule• Technical• economic

Initiation phase Analysis phase Design phase Implimentation Maintenance

Testing feasibility

intuitive v. scientific problem solving milestones PERT chart v. GANTT chart partitioning deliverables data flows information v. data context diagram

Terms