V&V activities can be understood in the form of a diagram which is described here, To understand this diagram, we first need to understand SDLC phases After this, verification and validation activities in those SDLC phases will be described. The following SDLC phases (see Fig. 1) are considered:

Requirements Gathering

The needs of the user are gathered and translated into a written set of requirements. These requirements are prepared from the user's viewpoint only and do not include any technicalities according to the developer.

Requirement Specification or Objectives

In this phase, all the user requirements are specified in developer's terminology. The specified objectives from the full system, which is going to be developed, are prepared in the form of a document known as software requirement specification (SRS).

Functional Design or High Level Design

Functional design is the process of translating user requirements into a set of external interfaces. The output of the process is the functional design specification, which describes the product's behaviour as seen by an observer external to the product. The high-level design is prepared with SRS, and software analysts convert the requirements into a usable product. In HLD, the software system architecture is prepared and broken down into independent modules. Thus, an HLD document will contain the following items at a macro level:

1. Overall architecture diagrams along with technology details

2. Functionalities of the overall system with the set of external interfaces

3. List of modules

4. Brief functionality of each module

5. Interface relationship among modules including dependencies between modules, database tables identified along with key elements.

Internal Design or Low-level Design

Since HLD provides the macro-level details of a system, an HLD document cannot be given to programmers for coding. So the analysts prepare a micro-level design document called internal design or low-level design (LLD). This document describes each and every module in an elaborate manner, so that the programmer can directly code the program based on this. There may be at least one separate document for each module.

Coding

If an LLD document is prepared for every module, then it is easy to code the module. Thus in this phase, using design document for a module, its coding is done.

After understanding all the SDLC phases, we need to put together all the verification activities. As described earlier, verification activities are performed almost at every phase; therefore all the phases described earlier will be verified, as shown in Fig. 32 Along with these verification activities performed at every step, the tester needs to prepare some test plans, which will be used in validation activities performed after coding the system. These test plans are prepared at every SDLC phase.

When the coding is over for a unit or a system, and parallel verification activities have been performed, then the system can be validated. It means validation activities can be performed now. These are executed with the help of test plans prepared by the testers at every phase of SDLC. This makes the complete V&V activities diagram (see Fig. 3).