- on site observations
I observed the store and its activities by visiting for some days
SYSTEMS DEVELOPMENT LIFE CYCLE (SDLC)
Every system has a life cycle, like that the human beings, plants or a product.
A System Development Life Cycle (SDLC) is an organizational process of developing an information system to solve business problems and needs.
SDLC means combination of various activities. In other words we can say that various activities put together are referred as SDLC. These various activities are called phases of the SDLC.
Following are the different phases of the SDLC:
- Problem Definition
- Feasibility Study
- System Analysis
- System Design
- Software Development
- Testing
- Implementation
- Maintenance
SDLC is also known as Classic Life Cycle Model, Linear Sequential Model or Water Fall Model.
Systems Analyst
Systems Analyst is the person who facilitates the development of information systems and computer applications.
Analyst must have the ability to listen; assess situations and draw conclusions; possess a strong general business orientation; speak and write effectively; prepare clear, concise reports; and work well with others to gain their respect and confidence.
Phases of the SDLC
Phase 1: Problem Definition
This phase provides a broad statement of user requirements, in user world terms - or what the user expect the system do - and thus sets the direction for the whole project.
This phase also sets the project bounds, which define what part of the system can be changed by the project and what parts are to remain the same. The resources to be made available to the system are also specified in this phase.
Phase 2: Feasibility Study
After a problem has been defined in the problem phase, the selection committee of the organization requests the information system department to a conduct a feasibility study to determine whether a project is technically and economically feasible.
The feasibility study determines the best method of achieve the objectives of new information system that would solve the problems.
The outcome of the feasibility study is the recommendation of a new system proposal. This new information system proposal is to be sanctioned by the higher management in consultation with department managers.
Phase 3: System Analysis
In this phase, the systems analysts study the existing system in detail, leading to specifications of a new system. This study is carried out by gathering data using following tools:
by inspecting written documents
- by conducting interviews,
- by questionnaires
- on site observations
Gathered data must be then analyzed and documented in the form of data flow diagrams (DFD), data dictionary (list of terms and their definitions), logical data structures and miniature specifications. System analysis also includes sub-division of the entire system into smaller sub-processes.
When all the systems requirements have been identified, the systems analyst produce a detailed report on the specifications of the new system.
Phase 4: System Design
This phase produces a logical design specification for the new system.
During this phase, the analyst schedules design activities, works with the user to determine the various data inputs to the system, plan how data will flow through the system, designs required outputs, and writes program specifications.
During this phase, analysts employ a variety of tools such as data flow diagrams, data dictionaries, and the Gantt chart (a graph depicting design events, personnel assignments, and time schedules).
During design, the analyst:
- Draws a model of the new system, using data flow diagrams (DFD) and entity-relationship (ER) diagrams.
- Devises formats for all the reports that the system will generate.
- Develops a method for collecting and/or inputting data.
- Defines the 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 the logical design phase, the analyst has prepared complete systems specifications in the form of a detailed report, with step-by-step instructions that describes the proposed system.
Phase 5: Software Development
The design specifications are converted into source code of a programming language. The programmers are responsible for carrying out activity. The software, which is to be developed, is divided in to many modules according to the sub-divisions in phase 3. The modules can be developed independently and then are to be tested individually. This type of testing is called unit testing. The test data are framed in such a manner as would ensure the entire modules can be tested.
Phase 6: Testing
Before actually implementing the new system into operation, developed system is to be test in order to remove all the bugs.
Two types of tests are conducted. These are as follows:
- Integration Testing
After completion of unit tests of all the modules, the modules are to be combined and be tested. At this stage the test is done on actual data.
- 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
After having the user acceptance of the new system developed, the implementation phase begins. This stage also involves two activities as follows:
The user training
The users are to be given training for operating a new information system. Main topics of such type of training are:
- How to execute the package
- How to enter the data
- How to process the data (processing details)
- How to take out the reports
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 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 the working of the organization, because the old system continues to work, as it used to do.
-
Phased implementation: The new system is introduced in phased manner.
-
Pilot implementation: In this implementation, the new system is installed in parts. Some part of the new system is installed first and executed successfully for considerable time period. When the results are found satisfactory then only other parts are implemented. This strategy builds the confidence and the errors are traced easily.
Phase 8: Maintenance
Maintenance is necessary to eliminate errors in the system during its working life and to tune the system to any variations in its working environment. It has been seen that there are always some errors found in the system that must be noted and corrected. It also means the review of the system from time to time. The review of the system is done for:
- knowing the full capabilities of the system
- knowing the required changes or the additional requirements
- studying the performance
If a major change to a system is needed, a new project may have to be set up to carry out the change. The new project will then proceed through all the above life cycle phases.
THREE VIEW OF THE SYSTEM
Logical data models (LDM)
Logical data models represent the abstract structure of some domain of information. They are often diagrammatic in nature and are most typically used in business processes that seek to capture things of importance to an organization and how they relate to one another. Once validated and approved, the logical data model can become the basis of a physical data model and inform the design of a database.
Logical data models should be based on the structures identified in a preceding conceptual data model, since this describes the semantics of the information context, which the logical model should also reflect. Even so, since the logical data model anticipates implementation on a specific computing system, the content of the logical data model is adjusted to achieve certain efficiencies.
The term 'Logical Data Model' is sometimes used as a synonym of 'Domain Model' or as an alternative to the domain model. While the two concepts are closely related, and have overlapping goals, a domain model is more focused on capturing the concepts in the problem domain rather than the structure of the data associated with that domain.
Data flow models (DFM)
A data-flow diagram (DFD) is a graphical representation of the "flow" of data through an information system. DFDs can also be used for the visualization of data processing (structured design).
On a DFD, data items flow from an external data source or an internal data store to an internal data store or an external data sink, via an internal process.
A DFD provides no information about the timing or ordering of processes, or about whether processes will operate in sequence or in parallel. It is therefore quite different from a flowchart, which shows the flow of control through an algorithm, allowing a reader to determine what operations will be performed, in what order, and under what circumstances, but not what kinds of data will be input to and output from the system, nor where the data will come from and go to, nor where the data will be stored (all of which are shown on a DFD).
Entity life histories (ELH)
It shows how information is changed during its lifetime
The jewellery system in flowchart
I am choosing the flowchart model for the jewelry system because it will be easy for end user to understand how flow is flowing and in which direction.
Task 2
Here is an overview of how the jewellery system works
When browsing your products, customers will usually have the option to either click on a product for more detailed information or add the product to the cart. When adding a product to the cart, the customer will also be able to select other required details, such as number, colour, size etc.
Once a product has been added to the cart, your customer will be taken to the cart's contents and be given the following options:
- Update the quantity (and other details as required)
- Remove a product
- Continue shopping
Once satisfied with the cart's contents, customers can then complete the secure order form. Submitting this form prompts the following actions:
- Sends an order confirmation email to the billing email address
- Displays details of the purchase back to the purchaser's browser
- Displays a personalised thank you message showing your appreciation
- Sends all order details to a Microsoft SQL Server database
- Sends an email with purchase details to you
Flowchart for the Jewellery store system
Assignment in System Analysis (module 2)
BTEC High National Diploma in Computing
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