CSE Information Systems 1 IMS 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 systems A system: l An inter-related set of components that interact to accomplish goals l system elements a boundary, a purpose, an environment, interfaces, input, processing, output, feedback, constraints

Information systems l 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. l It transforms Data into Information

l data input - recording information l data storage/retrieval - keeping information l data processing - transforming information l data output - displaying/presenting information Information System major functions

Benefits of an Information System l the right information l to the right degree of accuracy l when it is required l in the right format/layout l to the right people l 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 l 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 Cycle The SDLC provides: l a systematic and orderly approach to solving business problems l 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

11 Systems Development Phases Analysis Design Implementation Review Maintenance Quality Documentation Ethics Project Management Analysts Role Initiation

SDLC l phases l activities in each phase l output from phases

Systems Development Activities involved in building computer- based information systems are:- l identifying problems l analysing and describing information and processing needs l designing solutions to meet those needs l acquiring/building new systems l implementing new systems l maintaining information systems

Data Gathering The data gathered should include: l system description - how things work or should work l system problems - what is wrong or needs improvement l opportunities - identifying scope for innovation or new ways of doing things

Data gathering techniques l Interviews l Questionnaires l Observation l Reports l 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

calculate price 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

21 Levelling DFDs 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 processes e.g. Structured English, decision tables, decision trees Detailed Process Definitions

System design The 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 l to understand the business’s information needs what information is needed? for whom? in what form? when? l to describe the business’s information flows l to identify problems and opportunities l 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 l 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 l Initiation phase l Analysis phase l Design phase l Implimentation l Maintenance Testing feasibility

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