Systems Development Life Cycle(SDLC) - Phases And Activities Involved

Phase 1: Preliminary Investigation

1.1 Initial analysis( nature, scope, objective )
1.2 Feasibility study(economical, operational, and technical)
1.3 Suggest alternative solution( maintain, upgrade, change )
1.4 Initial report-( submit report to executives…..make decision to do or not)
 

Phase 2: System Analysis

2.1 Gather Data( Interview, questionare, sampling, observation)
2.2 Data Analysis( check list, carta grid, data flow, break down functions )
2.3 Report writing( about the present system, problem, need for a change)

Phase 3: System Design

3.1 Prepare few system designs( based on cost, technical, operational expertise, describe the new system as a collection of modules or subsystems.)
3.2 Select the best system( security, flexsibility, …prototype)
3.3 Report writing( cost and effect)

Phase 4: System Development

4.1 purchase software
4.2 purchase hardware
4.3 System is tested at various levels.

Phase 5: Implementation

5.1 Change to new system
5.2 Train the users
5.3 Evaluate the system

Phase 6: Maintenance

6.1 check smooth flow of system operation
6.2 improve system where necessary
6.3 conducting maintenance and enhancements as determined by periodic reviews

Duties of Personnel in System Development

Conceptual for Duties of Personnel in System Development

Information systems managers

-coordinate all the activities in IS
-responsible for the running of the system

Systems analysts

-determine the requirement for the IS according to the organisation

-analyse the input to the system

-do feasibility study

-help design in develop new system

Programmers

-analyse the requirement study from the system analyst and start the implementation phase.

End users

-non-information-system professionals in an organization.

-responsible in testing the developed system and then give feedback to system analyst.

Organisation of Files

Sequential files
When records are arranged physically in a certain order, the file is said to be a sequential file.
-when the file is updated, it is necessary to go through the entire file
-sequential organization would make sense when many records need to be read or modified.
-all records have the same size and the same field format and the records are sorted in the file according to the content of a field called key.
-the files can be saved both on a disk or on a tape.
-disadvantage : Adding or deleting records become physical.

Random files
Records in a file can be accessed directly without reference to the other records in the file 
-provides a much faster access.
-the records can be scattered over the disk space in any order.

Indexed files
The rows are stored either sequentially or non-sequentially 
-an index is created that allows software to locate individual rows.
Index – a table used to determine the location of rows in a file that satisfy some condition.

Types of Information System

1.Transaction processing system (TPS)

A TPS collects and stores information about transactions, and controls some aspects of transactions. A transaction is an event of interest to the organisation.

A TPS is a basic business system. It:

·         serves the most elementary day-to-day activities of an organisation;

·         supports the operational level of the business;

·         supplies data for higher-level management decisions.

·         mostly for predefined, structured tasks

·         can have strategic consequences (eg airline reservation system)

·         usually has high volumes of input and output

·         provides data which is summarised into information by systems used by higher levels of management

·         need to be fault-tolerant.

On-line transaction processing: A transaction processing mode in which transactions entered on-line are immediately processed by the CPU.

2.Management information system (MIS)

converts TPS data into information for monitoring performance and managing an organisation. Transactions recorded in a TPS are analyzed and reported by an MIS.

They have large quantities of input data and they produce summary reports as output. Used by middle managers. An example is an annual budgeting system.

 3.Decision support system (DSS)

helps strategic management staff (often senior managers) make decisions by providing information, models, or analysis tools. For support of semi structured and unstructured decisions (structured decisions can be automated). Used for analytical work, rather than general office support.

They are flexible, adaptable and quick. The user controls inputs and outputs. They support the decision process and often are sophisticated modeling tools so managers can make simulations and predictions.

4.Expert system (ES)
a computer system or program that uses artificial intelligence techniques to solve problems that ordinarily require a knowledgeable human. The method used to construct such systems, knowledge engineering, extracts a set of rules and data from an expert or experts through extensive questioning. This material is then organized in a format suitable for representation in a computer and a set of tools for inquiry, manipulation, and response is applied. While such systems do not often replace the human experts, they can serve as useful adjuncts or assistants.

Expert systems imitate human experts in many different fields of expertise. Such systems contain rules (such as decision tables) that help a human answer expert questions.

Advantages of expert systems:

·         The computer can store far more information than a human.

·         The computer does not 'forget', make silly mistakes or get drunk when it is most needed.

·         Data can be kept up-to-date.

·         The expert system is always available 24 hours a day and will never 'retire'.

·         The system can be used at a distance over a network.

5. Executive information System(EIS)

A type of management information system to facilitate and support the information and decision- making needs of senior executives by providing easy access to both internal and external information relevant to meeting the strategic goals of the organization.commonly considered as a specialized form of a Decision Support System

emphasize on graphical displays and easy-to-use user interfaces. offer strong reporting and drill-down capabilities.

Generally, it is a enterprise-wide DSS that help top-level executives analyze, compare, and highlight trends in important variables so that they can monitor performance and identify opportunities and problems. 

The purpose was to package a company’s data and to provide sales performance or market research statistics for decision makers, such as financial officers, marketing directors, and chief executive officers, who were not necessarily well acquainted with computers.

Advantages :

ž  -Easy for upper-level executives to use.

ž  -Provides timely delivery of company summary information.

ž  -Information that is provided is better understood.

ž  -Filters data for management.

ž  -Improves to tracking information.

ž  -Offers efficiency to decision makers.

Disadvantages :

ž  -System dependent.

ž  -Limited functionality, by design.

ž  -Information overload for some managers.

ž  -Benefits hard to quantify.

ž  -High implementation costs.

ž  -System may become slow, large, and hard to manage.

ž  -Need good internal processes for data management.

ž  -May lead to less reliable and less secure data.

Data Integrity

-the assurance that data is consistent and correct.
-term that can mean ensuring data is "whole" or complete
-the condition in which data are identically maintained during any operation
-the preservation of data for their intended use

Data Validation

-the confirmation by examination and the provision of Objective evidence that the particular requirement for a specific intended use are fulfilled.
-a process by which a procedure is evaluated to determine its efficiency and reliability. (to demonstrate that a method is suitable for its intended purpose)

Data Dictionary /Language

Data Dictionary
Provides detailed accounting of all tables found within the user/designer-created database
-contains (at least) all the attribute names and characteristics for each table in the system
-contains metadata—data about data
-sometimes described as “the database designer’s database” because it records the design decisions about tables and their structures

Data Definition Language (DDL)
Used to built data, define data types and data structure in a database.
-describes the records, fields, and "sets" making up the user Data Model

Data Manipulation Language (DML)
Is that of SQL, which is used to retrieve and manipulate data in a Relational database. Comprises the 'SQL-data change' statements, which modify stored data but not the schema or database objects
-have their functional capability organized by the initial word in a statement, which is almost always a verb. In the case of SQL, these verbs are:

SELECT 

INSERT 

UPDATE 

DELETE