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Entity-Relationship Diagrams ER-modeling is a data modeling method used in software engineering to produce a conceptual data model of an information system. Diagrams created using this ER-modeling method are called Entity-Relationship Diagrams or ER diagrams or ERDs. Purpose of ERD The database analyst gains a better understanding of the data to be contained in the database through the step of constructing the ERD. The ERD serves as a documentation tool. Finally, the ERD is used to connect the logical structure of the database to users. In particular, the ERD effectively communicates the logic of the database to users. Components of an ER Diagrams 1. Entity An entity can be a real-world object, either animate or inanimate, that can be merely identifiable. An entity is denoted as a rectangle in an ER diagram. For example, in a school database, students, teachers, classes, and courses offered can be treated as entities. All these entities have some attributes or properties that give them

Software Requirement Specifications The production of the requirements stage of the software development process is  Software Requirements Specifications (SRS)  (also called a  requirements document ). This report lays a foundation for software engineering activities and is constructing when entire requirements are elicited and analyzed.  SRS  is a formal report, which acts as a representation of software that enables the customers to review whether it (SRS) is according to their requirements. Also, it comprises user requirements for a system as well as detailed specifications of the system requirements. The SRS is a specification for a specific software product, program, or set of applications that perform particular functions in a specific environment. It serves several goals depending on who is writing it. First, the SRS could be written by the client of a system. Second, the SRS could be written by a developer of the system. The two methods create entirely various situations and es

Prototype Model The prototype model requires that before carrying out the development of actual software, a working prototype of the system should be built. A prototype is a toy implementation of the system. A prototype usually turns out to be a very crude version of the actual system, possible exhibiting limited functional capabilities, low reliability, and inefficient performance as compared to actual software. In many instances, the client only has a general view of what is expected from the software product. In such a scenario where there is an absence of detailed information regarding the input to the system, the processing needs, and the output requirement, the prototyping model may be employed. Steps of Prototype Model Requirement Gathering and Analyst Quick Decision Build a Prototype Assessment or User Evaluation Prototype Refinement Engineer Product Advantage of Prototype Model Reduce the risk of incorrect user requirement Good where requirement are changing/uncommitted Regula

V-Model V-Model also referred to as the Verification and Validation Model. In this, each phase of SDLC must complete before the next phase starts. It follows a sequential design process same as the waterfall model. Testing of the device is planned in parallel with a corresponding stage of development. Verification:  It involves a static analysis method (review) done without executing code. It is the process of evaluation of the product development process to find whether specified requirements meet. Validation:  It involves dynamic analysis method (functional, non-functional), testing is done by executing code. Validation is the process to classify the software after the completion of the development process to determine whether the software meets the customer expectations and requirements. So V-Model contains Verification phases on one side of the Validation phases on the other side. Verification and Validation process is joined by coding phase in V-shape. Thus it is known as V-Model.

Spiral Model The spiral model, initially proposed by Boehm, is an evolutionary software process model that couples the iterative feature of prototyping with the controlled and systematic aspects of the linear sequential model. It implements the potential for rapid development of new versions of the software. Using the spiral model, the software is developed in a series of incremental releases. During the early iterations, the additional release may be a paper model or prototype. During later iterations, more and more complete versions of the engineered system are produced. The Spiral Model is shown in fig: Each cycle in the spiral is divided into four parts: Objective setting:  Each cycle in the spiral starts with the identification of purpose for that cycle, the various alternatives that are possible for achieving the targets, and the constraints that exists. Risk Assessment and reduction:  The next phase in the cycle is to calculate these various alternatives based on the goals and c

Waterfall model Winston Royce introduced the Waterfall Model in 1970.This model has five phases: Requirements analysis and specification, design, implementation, and unit testing, integration and system testing, and operation and maintenance. The steps always follow in this order and do not overlap. The developer must complete every phase before the next phase begins. This model is named " Waterfall Model ", because its diagrammatic representation resembles a cascade of waterfalls. 1. Requirements analysis and specification phase:  The aim of this phase is to understand the exact requirements of the customer and to document them properly. Both the customer and the software developer work together so as to document all the functions, performance, and interfacing requirement of the software. It describes the "what" of the system to be produced and not "how."In this phase, a large document called  Software Requirement Specification (SRS)  document is created