Phases of Waterfall Model

• Concept formation
• Problem definition
• Feasibility study
• System analysis and specification
• System design
• Broad design
• Detailed design
• System development
• Development
• Implementation
• System testing
• Maintenance

Waterfall model

Waterfall model is one of the simplest model used in software development process. This is suitable to well defined systems and centers around planed processes. Waterfall model also known as the liner model because it is an execution of sequential activities or processes. One process start only after completion of the immediate previous process. Each phase produces a detailed document for the next phase. Team members assigned for the each level and they are responsible for the accurate self completion of the assigned phase.

This model is generally time consuming and requires a good documentation and debugging (error handling) could becomes difficult for large systems. Because an error could be flows in to many above levels in the system testing phase.

Software Development Process

Software Development Process means all the activities involved in developing an information system or simply called a software. This is also called as software development life cycle or system development life cycle. You have to remember that term "software life cycle" is a different term and not same as "software development life cycle". Therefore it is better to use the term "software development process" instead of other terms, but you should know all the terms.

Basically we can divide this process in to four main processes.

1. Software specification - also refer as system specification. It is same as we define a computer system such as processor speed, memory, hard drive, etc. Software specification is a document which includes all user requirements, functionality,  operations, etc. Previously we speak about system boundary. Generally speaking software specification is a detailed report of system boundary.
2. Software development - according to the software specification, designers and developers together develop the system.
3. Validation (testing) - After the development, software should be tested against the specification to ensure that it meets all requirements and to identify errors and ensure it is working without errors.
4. Software evolution - after validation, there will be future changes to be done according to customer requirements. This is an ongoing process until a new version release or develop a completely new system.

What is an information system?

An information system is a systematic arrangement of people, processes, data and interfaces that are integrated for the purpose of supporting an organization's day to day activities as well as supporting the purpose of decision making and problem solving for managers.

Now you need to understand this concept by your own words. If you can define the above definition in your own way then only you can satisfy yourself that you really know that is an information system.

An information system is basically made of people, processes, data, and interfaces. Geography also can be consider as one component. Let me explain these one by one;

Peoples are the users of an information system. Why an information system need to people? For employees, to perform their day to day activities such as input customer or sales data, print receipts, etc. For managers and other above levels, to make decisions, planing, or solve a problem. They need reports (processed data). Interfaces are required to enter data and generate reports. Geography can be consider as a system need to interact with peoples in different locations. So, processes are required to do all these things in a systematic way.

Factors to be considered when developing a system

There are few basic factors to be considered when developing an information system. You need to clearly identify these factors in an organization.

• Objective - You need to understand what exactly the intended system is supposed to do? This is including input data, reports, charts, etc. Also you need to understand the business process of the organization.
   
• System boundary - Every requirements / components that make up the system. Later we can define this as the system domain. System boundary is very important to plan a project and costing.
  
• System Environment - Everything outside the system boundary is known as the system environment. In an information system these can be legal and law enforcements, ethics, practices, regulations, etc. This is important when you developing a system, you need to do it according to the system environment. As an example, if you are developing a system which deals with money transactions, you need to have an understanding about the environment of legal and other aspects.
  
• Sub systems - This is specially involves in the system designing process. A system can be made of many small parts called sub systems. According to the programming methods, these sub systems are called in different names such as modules, functions, etc. You will learn about these sub systems in details later. Sub systems are important to reduce the complexity of a system. Reducing complexity give you many advantages such as easy to develop, troubleshoot, manage, etc.
  
• People - One of the most important component in a system is people. Because all the system we made for peoples. In a system people can be divided in to many segments. The most important party is system users. System users can be employees, customers, suppliers, etc. Some times there are other peoples that are not system users such as government authorities, media, etc has to be considered in special situations.
  
• Data - The other most important factor of a system. Data can be input or output. When developing a system organization of data is very important. You need to organize your system data in a error free, easy to locate method.
  
• Database - Database comes when you want to organize your system data in a proper way. This can be refer as a structured repository of related data.