SYSTEM LIFE CYCLESystem life cycle is an organizational process of developing and maintaining systems. It helps in establishing a system project plan, because it gives overall list of processes and sub-processes required for developing a system.System development life cycle means combination of various activities.In other words we can say that various activities put together are referred as system development life cycle. In the System Analysis and Design terminology, the system development life cycle also means software development life cycle.
Following are the different phases of system development life cycle:• System investigation• Feasibility study• System analysis• System design• Coding• Testing• Implementation• Maintenance
PHASES OF SDLC SYSTEM INVESTIGATION Feasibility study Maintenance System AnalysisImplementation SDLC System Design Testing Coding
S Y S T E M I NV E S T I GA T I ONSystem investigation is the first stage of system development life cycle.This phase is intended to be quick .
Business Community 1.List Problems, Steering Community oppurtunities and directives Data Store Present the 2.Determine scope Project Plan Project is 4.Plan the worthy 3.Assess project Project worth
1.To determine whether a business problem or opportunity exists.This involves identify the problem, estabilish an initial baseline of the problems,oppurtunities and directives that triggered the project.Listing constraints such as project deadlines,maximum budget,general technology.System analyst or project manager leads this task.
2. Define the scope of the project.Scope defines the boundary of the project and can be easily defined within the context of your information system building blocks.Scope can be described in terms of:What types of data describe the system being studied?What business processes are included in the system?How must the system interface with the users ?
3. Assess project worthIs this project worth looking at?Will it solve the problems?Is this beneficiary?4.Plan the ProjectThe initial project plan should consists of atleast the following:A preliminary master plan that includes schedule and resource assignments for the entire project.This plan will be updated at the end of each phase of the project.This is sometimes called a baseline plan.
A detailed plan and schedule for completing the next phase of the project.The task is responsibility of the project manager.5.Present the project and plan.Present the estimated project plan to the steering body for approval.A steering body is a committee of executive business and system managers that studies and prioritizes competing project proposals to determine which project will the most value to the organisation and thus should be approved for continued system development.
FEASIBILITY STUDYThe goal of feasibility study is to evaluate alternate systems and to propose the most feasible and desirable system for development.Feasibility Study is essential to evaluate cost & benefits of the proposed system
Technical FeasibilityFollowing things should be considered: Determine available hardware. Determine available computer with configuration. Determine available software.Find out technical feasibility required for proposed system1) Mention new hardware requirements of proposed system.2) Mention Computer with new configuration requirements of proposed system.3) Mentions New software requirements of the proposed system.
Operational FeasibilityIt finds whether the operations of proposed system is easy or not as compare to existing system.It find out whether the user or customer of the system requires extra training or notSystem should provide right & accurate information to user or customer at right place as well as at right time.
Economical FeasibilityWhether expected cost savings, increased revenue, increased profits and other type of benefits will exceed the cost of developing and operating a proposed system.
Motivational FeasibilityThe probability that the organisation is sufficiently motivated to support the development and implementation of the application with necessary user participation,resources,training time etc.
Schedule FeasibilityThe probability that the organisation can complete the development process in the time allowed for development
Cost / Benefit AnalysisFeasibility studies involve cost / benefit analysis.If costs and benefits are quantified, they are called tangible.If not they are intangible.Tangible benefits are favourable results.Intangible benefits are harder to estimate. Such benefits are better customer service or faster and more accurate information for management to fall into this category.
TANGIBLE BENEFITS1. Increase in sales or profits.2. Decrease in information processing costs.3.Decrease in operating costs.4. Decrease in required investment.5. Increased operational ability and efficiency.
INTANGIBLE BENEFITS1. New or improved information availability.2. Improved abilities in computation and analysis.3. Improved customer service.4. Improved employee morale.5. Improved management decision making.6. Improved competitive position.7. Improved business and community image.
SYSTEM ANALYSISInvolves a detailed study of:1.The information needs of the organisation and end users.2. The activities,resources and products of any present information.3. The information system capabilities required to meet the information needs and those of other end users.
1.Organisational AnalysisTo know something about the organisation,its management,structure,its people, its business activities, the environmental systems it must deal with and its current information systems.Conduct a detailed study of specific end user department that will be affected by the new or improved information system being proposed.
2. Analysis of present systemBefore designing a new system , it is important to study the system that will be improved or replaced(if there is one).Analyse how this system uses hardware, , software, network, and people resources to convert data resources such as transactions data into information products, such as reports and displays.Also note how the information system activities of input,output,storage,control are accomplished.
3.Functional Requirement AnalysisTo determine what type of information you require,what its format,volume, and frequency should be and what response times are necessary.To determine the information processing capabilities required for each system activity to meet these information needs.Goal is to determine what should be done.Try to develop the functional requirements like:
a . User Interface requirements : The input output needs of end users that must be supported by the information system, including sources, formats,content, volume, and frequency of each type of input and output.b. Processing requirements : Activities required to convert input to output. Includes calculations,decision rules, and other processing operations, and capacity .Also find throughput,turnaround time and response time needed for processing activities.
c. Storage requirements : Organisation content and size of databases, types and frequency of updating and retrieving records.d. Control requirements :Accuracy,validity, safety, security and adaptability requirements for system output, processing, input and storage functions.
SYSTEM DESIGNSystem analysis describes what a system should do to meet the information needs of users.System design specifies how the system will accomplish this objective.System design consists of design activities that produce system specifications satisfying the functional requirements developed in the system analysis stage.
Elements of system designData Flow : The movement of data in and out of the system.Data Stores : Temporary or permanent collection of data.Process : Activities to accept manipulate and deliver data and information.Procedures : Methods and routines for using the information systems.Controls : These are standards and guidelines for determining the activities.Roles : The reponsibilities of all persons.
System design focuses on 3 activitiesUSER DATA PROCESSINTERFACE DESIGN DESIGN DESIGNScreen,form Data element ProgramReports, Structure andDialog designs design structure design
User Interface DesignFocuses on designing the interaction between end users and computer systemsDesigners concentrate on input/output methods and the conversion of data and information between human readable and machine readable forms.Prototyping process in which user interface methods are designed and modified with feedback from end users.It produces detailed specification for information products such as display screens,interactive user/ computer dialogues,audio responses,forms, documents and reports
Data DesignFocuses on design of the structure of databases and files to be used by a proposed system.Data design produces a data dictionary which includesa.The attributes or characteristics of the entities (objects,people,places,events) about which the proposed system needs to maintain information.b. The relationships these entities have to each other.
c. The specific data elements(dbs,files, records) that need to maintained for each entity tracked by the system.d. The integrity rules that govern how each data element is specified and used in the system.
Process DesignFocuses on the design of software resources ie, programs and procedures needed by the proposed system.Process design produces detailed program specifications and procedures needed to meet the user interface and data design specifications that are developed.Process design must also produce specifications that meet the functional control and performance requirements developed in the analysis stage.
System SpecificationsThe design of user interface methods and products , database structures and processing and control procedures results in hardware,software, network, data and personnel specifications for a proposed system.User interface specification: The content , format, and sequence of user interface products, and methods such as display screens, interactive dialogs, audio responses, forms, documents and reports.
Database Specifications : Content, structure, distribution and access, response, maintenance, and retention of db.Software Specifications: The required s/w package or programming specifications of the proposed system including performance and control specifications.Hardware and network Specifications:The physical and performance characteristics of the equipment and networks required by the proposed system..Personnel Specification: Job description of persons who will operate the system.
Design of outputOutput generally refers to the results and information that are generated by the system.When designing output, system analyst must accomplish the following:1. Determine what information to present.2. Select the output medium.3. Arrange the presentation of information.4. Decide how to distribute the output to intend recipients.
What factors contribute to high quality, useable information(output)?Timeliness - is it available in time?Relevance - is it helpful?Accuracy - is it error-free?Accessibility - how easy is it to use?Useability - is it in an acceptable format?
Types of outputReportsDocumentsMessagesOutput contents originate from these sources.Retrieval from a data store.Transmission from a process or system activityDirectly from an input source.
Output ObjectivesConvey information about past activities, current status, or projections of the future.Signal important events, oppurtunities, problems or warnings.Confirm an action.
Design of inputSystem analyst decide the following input design details: - Input data - Medium of use. - Arrangement of data - Guidelines for users. - Data items needing validation and steps to follow when errors occur.
Objectives of input design- Controlling amount of input.- Avoiding delay.- Avoiding errors in data.- Avoiding extra steps.- Keeping the process simple.
Design of FilesIt includes decisions about the nature and content of the file itself such as whether it is to be used for storing transactions details, historical data or reference information.Which data items to include in a record form within the file?Length of each record based on the characteristics of the data items on which it is based.The arrangement of records in the file.