Unit 3 : Information Systems
Conducted by: Computer Science Society Of University Of Colombo Parakrama Ratnayake
What is a System ? It is a collection of interrelated
c omponents that work together to components perform a specific task. e.g. : Human Body Business Organization A Computer
Sub Systems ? In a System the different components are connected with
each other and they are interdependent. Each component is a Sub S ystem of the original system ystem System and carries out part of the systems tasks. e.g. : Parts like digestive system in the human body The marketing branch of a business organization
Elements of a System Input
Output Processing
Basically there are three major components in every system, namely input , processing and processing and output . The System is separated from the external environment from the system boundary. The system receives inputs from a its environment and returns outputs to the environment by processing the inputs.
Input
Output
•Sub systems should communicate with each other in order to process an output to a particular input.
•One subsystems output will be an input to another.
•A good system will be made up of highly independent subsystems with minimal flows between them.
DATA vs. INFORMATION Data Raw facts in isolation. Data describe the business. These are isolated facts convey meaning but generally are not useful by themselves. t hemselves.
Information is data that has been manipulated to be useful to someone. In other words, information must have value, or it is still s till data. Information tells people something they don’t already know or confirms something that is suspect. Important facts • Most people use the terms data and information interchangeably. But data and information are not the same thing. •
One person’s information may be another person’s data.
Information System An arrangement of people, data, processes,
interfaces, networks and technology that are integrated for the purpose of supporting and improving the day to day operations in a business, as well as fulfilling the problem solving and decision making information needs of business managers. Two Main Types of Information Systems Manual Information Systems Computer Based Information Systems
Manual Information Systems File storage devices, manual procedures and papers are examples of components of a manual information system.
Computer bases Information System Involves six interdependent components: Hardware (machines) Software (instructions & programs) People (programmers, managers and users) Procedures (rules) Data & Information
Pros & Cons of a Manual Information System Pros
Flexible Judgments & Decisions can be taken easily by humans
Cons
Humans are unreliable Slow in performing arithmetical operations
Subjected to fatigue and boredom
Levels of Management Upper or Top or Strategic Management Strategic Middle or Tactical Management Tactical Lower or Operational level Management
Operational
Three levels of management
Levels of Management cont.. Each level of management can be distinguished by the types of Decisions made Time frame considered in the decisions Types of report information needed to make
decisions
Lower or Operational level Management They make structured decisions (Operational decisions).
Structured decision It’s a predictable decision that can be made following a well defined set of routine procedures. Most decisions at this level require easily defined information that relates to the current status and a nd activities within the basic business functions. Information is gained from detailed reports which contain information about routine activities. Detailed tasks defined by middle management are carried out by people at operational level.
Middle or Tactical Management Acquire and arrange the resources (Computers, people etc) to meet
the goals of an organization. Define the detailed tasks to be carried out at the operational level. Information needed involves review, summarization and analysis of data to help plan and c control ontrol operations and implement policy that has been formulated by upper management. Information is usually given to middle managers as summarized reports. Deals with semi structured decisions. (Tactical decisions)
Semi structured decisions that must be made without a base of clearly defined informational procedures. In most cases a semi structured str uctured decision is complex, requiring detailed analysis and extensive computations.
Upper or Top or Strategic Management Decides on the broad objectives of an
organization. Make unstructured decisions. (Strategic decision).
Unstructured decisions are the most complex type of decisions and are rarely r arely based on predetermined routine procedures. They involve subjective judgments of the decision maker.
Types of Information Systems •Transaction processing systems (TPS) •Management Information Systems (MIS) •Decision support Systems (DSS) •Executive Information Systems (EIS) •Expert Systems (ES)
Transaction Processing Systems (TPS) •These systems capture and process data about business transactions. •Some times called as data processing systems •Mostly used at operational level •Usually creates detailed reports of daily transactions or future transactions •Reports generated are useful only to lower level managers •One functional area of a business consists of an TPS
Management Information Systems (MIS) •Provides middle level management with reports that summarize and categorize information derived from company databases. (In pre determined format) •Supplements Transaction processing Systems •Able to produce detailed information, summary information, exception information •Information produced is based on accepted management or mathematical/statistical models
Decision Support Systems (DSS) •Provides its users with decision oriented information whenever a decision-making situation arises •Analyses information already captured by TPS and MIS in order to support unstructured decision making at top management level •Facts •DSS does not make decisions, it helps some one to make a decision by providing information •TPS or MIS does not analyze information they produce
Executive Information System (EIS) •Is a DSS which is especially meant for top level management and specifically support unstructured decision making •Also called Executive Support Systems (ESS) •Draws data not only from the organization, able to draw information from outside sources such as news services and marketing –research databases.
Expert Systems (ES) •Captures knowledge expertise of a problem solver or decision maker and then simulates thinking of that expertise for those who have less expertise. •Includes logic and reasoning within there respective fields •Facts •Emerged from the filed of artificial art ificial intelligence (Creating computer systems that simulate human reasoning and sensation)
System Development Life Cycle (SDLC) Problem Definition
Maintenance
Feasibility Study
System Analysis
Implementation
System Design
Testing Software Development
SDLC cont.. Every system has a life cycle. Be it a computer
or human SDLC is an organizational process of developing devel oping dev eloping an information system to solve business problems and needs SDLC means combinations of various activities. These activities are called phases and the SDLC consists of many phases Also called Classical Life Cycle Model, Linear Sequential Model or Water Fall Model Model
Phase 1: Problem Definition •Provides a broad statement of user requirements, which in other words is what the user expects the systems to do •Sets the direction for the whole project •Also sets the project bounds, which define what part of the t he system can be changed by the project and what parts remain the same •The resources to be made m ade available available to the system are also specified in this phase
Phase 2 : Feasibility Study •Determines whether a particular project is technically technically and and economically feasible economically feasible •Determines the best method to achieve the objectives of the new information system •Outcome of this phase is a recommendation of a new system proposal •This proposal is to agreed by the higher management m anagement in consultation with department managers.
Phase 3 : System Analysis •System analysts studies the existing system in detail, leading to specifications of a new system. This is carried carr ied out by gathering facts. Facts gathering techniques •
Inspection of written documents
•
Interviews
•
Questionnaires
•
Site Observations
•Gathered data must be analyzed and documented in data flow diagrams, data dictionary, logical data structures and miniature specifications. •The system is broken down into smaller sub processors during this phase. •At the end of the phase the System S ystem analyst has to produce a detailed report on the specifications of the new system.
System Analyst Person who facilitates the development of information systems and computer applications He/ She should be able to Asses situations and draw conclusions Possess a strong general business orientaion Speak and write effectively Prepare clear concise reports Work well with others to gain confidence and respect from them
Phase 4 : System Design Produces a logical design specification for the new system. The analyst schedules works plan
design activities
with user to determine the various data inputs to the system
how data will flow through the system
designs writes
required outputs
program schedules
During design, the analyst Draws
a model of the new system, using dataflow diagrams and entity relationship diagrams Devises
formats for all the t he reports that the system will generate
Develops
a method for collecting and inputting data
Phase 4 : System Design contd.. By the end of this phase the analyst has to t o contd.. Defines detailed data requirements with a data dictionary Writes program specifications Specifies control techniques for the system’s outputs, database and inputs Identifies and orders any hardware or software that the system will need
By the end of this phase the analyst has to to prepare complete systems specifications in form of a detailed report (this report contains step by step instructions that describes the proposed system)
Phase 5 : Software Development •Design specifications are converted into source code of a programming language. •Programmers carry out these tasks. •Software that is to be developed, is divided into many modules according to the subdivisi s ubdivisions ons in phase 3. These modules are created independently and then tested individually. individu ally. This type of testing is called unit testing) t esting)
Phase 6 : Testing The system should be fully tested for errors error s (bugs) before implementation. Two types of tests are conducted 1. Integration testing After completion of unit tests of all modules, the modules are to be combined and be tested. At this stage st age the test is done on actual data 2. Acceptance testing Acceptance criteria is the agreement made between the user and the system developer. The acceptance criteria contains a list of important requirements that the system has to satisfy. The tests conducted to check the acceptance criteria are called acceptance testing.
Phase 7 : Implementation The phase contains two activities 1. The user training The users are to be given training tr aining for operating a new information system. Main topics of such type of training are How to execute the package How to enter data How to process data How to take reports 2. The conversion The process of replacing an existing system with a new system is called conversion. Conversion of the system may proceeds in four ways.
Direct Implementation The entire system is replaced with the new system in one go. Parallel Implementation Both systems i.e. the new and the old systems are executed in parallel for a certain cer tain defined period of time. This strategy is helpful because of the following
Results of the old system can be compared with the results of the new system Failure of the new system at the early stage, does not affect working of the organization
Phased implementation The new system is introduced in a phased manner Pilot implementation New system installed in parts and executed successfully for a considerable time period. When the results are found satisfactory then only the other parts are implemented
Phase 8 : Maintenance Eliminates errors in a system during it’s life time tim e time
and to tune the system to any variations. It also means the review of the system from time to time.
The review is done for Knowing the full capabilities of the system Knowing the required changes or the additional requirements Studying performance
If a major change to a system is needed a new
project may have to be setup.
Problems in system development Estimating cost and time Selecting a project team Capturing user requirements Using standards Choosing design approaches Coding program Testing programs Maintaining systems
