CSE Information Systems 1 Revision

Subject Overview System concepts and information systems Systems development and the SDLC Information gathering Modelling Process modelling using DFDs Low-level processes: minispecs

Subject Overview System design principles Communicating using documentation and presentations Working in teams Ethics and professional practice 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 components, inter-related components, 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 complexity 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

Any information system performs four main functions: l data input - recording information l data storage/retrieval - keeping information l data processing - transforming information l data output - displaying/presenting information Functions of an Information System

Benefits of an Information System A good information system ensures:- 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

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 external requirements or pressures, e.g. 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

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

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 l what is technically possible l what constraints exist

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 process modelling graphically represents the processes which act on data to capture manipulate store distribute

Process modelling 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

18 2 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 levelling of DFDs improves their readability and usefulness as a communication tool Levelling Data Flow Diagrams

20 Levelling DFDs Context diagram Level zero diagram Diagram 1 (at level 1)

Data flow diagrams may focus on either: the “physical” view of the system’s processing OR the “logical” view of the system’s processing Logical and physical DFDs

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...

Systems design features Design features that lead to more correct systems that are easier to maintain and modify: Small module size.. easier to write and test, and they are less likely to affected by change Modular independence (coupling).. the less the inside of one module depends upon another, the easier it will be to test and maintain Modular strength (cohesion).. measures the strength of association of elements within a module “black box” characteristics

Documentation Not necessarily a piece of paper. Any permanent medium used to communicate to other people can be classed as documentation Product and documentation should be developed at the same time DOCUMENTATION IS PART OF THE PRODUCT Documentation is communication: the objective is to: create a specific effect on particular readers who want specific information, have particular characteristics and will read under particular circumstances.

Presentations person to person communication high credibility single purpose relatively short duration a once-only event 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

systems development is a team effort teams are organised on a project basis team membership can include: IT managers, systems analysts, users, business managers, programmers, and other specialists at various points in the project Teams in systems development

Project manager - manages the project Analysts/designers - the architects who decide how the system will look and work Programmers/database/network designers - the builders who make and put together the system components Operations/systems administration/data communications - the operational people who look after the technology infrastructure to make the system run Computing People in the SDLC

Senior managers - who decide what the organisation’s needs and priorities are and allocate resources accordingly Middle managers - who decide how their part of the organisation runs, allocate resources accordingly and advise or seek support from senior management when necessary End users (operational staff) - who do the work Business 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 Select systems development methodology Plan the project tasks Estimate the resources and time required to complete individual phases of the project Staff the project team Organise and schedule the project effort(tasks/time/ people/technical resources) and therefore cost Control the project development (directing the team, controlling progress, replan, restaff,.... )

Quality in systems development various definitions e.g. 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 implementing quality: e.g. standards, technical reviews

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

l each type of system has its own literature, technology, specialist skills, etc l each type of system is allied with other disciplines l a large and ever-expanding range of specialised software is available for these types of systems l each type of system requires a particular set of technical skills to develop them l different types of system tend to have different types of key users involved in their development Types of Information Systems