Software Development Life Cycle(SDLC)
It is a procedure to develop the software.
It is a process of creating or altering systems and the models and methodologies that people use to develop these systems.
Any SDLC should result in a high quality system that meets or exceeds customer expectations, reaches completion within time and cost estimates, works effectively and efficiently and is inexpensive to maintain and cost effective to enhance.
Different procedures / models are available to develop a software namely,
1) Waterfall model
It is a traditional model, It is a sequential design process, often used in SDLC, in which the progress is seen as flowing steadily downwards (like a waterfall), through the different phases as shown in the figure,
1.Feasibility Study :-
- done by software team consisting of project managers, business analysts, architects, finance, HR, developers but not testers
- architect — is the person who tells whether the product can be developed and if yes, then which technology is best suited to develop it.
— technical feasibility — financial feasibility — resource feasibility
2. Requirements Collection :-
- done by Business Analysts and Product Analysts
- gathering requirements
- translates business language into software language
For ex, let us consider the example of a banking software.
3. Design :-
There are 2 stages in design,
HLD — High Level Design
LLD — Low Level Design
HLD — gives the architecture of the software product to be developed and is done by architects and senior developers
LLD — done by senior developers. It describes how each and every feature in the product should work and how every component should work. Here, only the design will be there and not the code.
4. Coding / Programming :-
— done by all developers — seniors, juniors, freshers
— this is the process where we start building the software and start writing the code for the product.
5. Testing :-
- done by test engineers
— it is the process of checking for all defects and rectifying it.
6. Installation :-
- done by installation engineers
- to install the product at a client‟s place for using after the software has been developed and tested.
For ex, consider the example of a software to be developed and installed at Reliance petrol bunk.
7. Maintenance :-
- here as the customer uses the product, he finds certain bugs and defects and sends the product back for error correction and bug fixing.
2. SPIRAL MODEL
The spiral model is shown in the figure in the next page.
Ra- requirements analysis of module A. Similarly with Rb, Rc, Rd.
Da – design of module A. Similarly with Db, Dc, Dd
Ca – coding of module A. Similarly with Cb, Cc, Cd
Ta – testing of module A. Similarly with Tb, Tc, Td
In Spiral model, the software product is developed in small modules. Let us consider the figure shown below in developing a s/w product X. X is built by integrating A,B,C and D.
The module A – requirements of the module is collected first and then the module is designed. The coding of module A is done after which it is tested for defects and bugs.
The module B – once module A has been built, we start the same process for module B. But while testing module B, we test for 3 conditions – a)test module B b)test integration of module B with A c)test module A.
The module C – after building module A,B, we start the same process for module C. Here we test for the following conditions – 1) test module c, b, a 2) test for integration of C and B, C and A, A and B.
And thus the cycle continues for different modules. Thus in the above example, module B can be built only after module A has been built correctly and similarly for module C.
Advantages of Spiral Model :-
1) Requirement changes are allowed.
2) After we develop one feature / module of the product, then and only then we can go on to develop the next module of the product.
Drawbacks of Spiral Model —
Traditional model and thus developers only did testing job as well.
Applications of Spiral Model
- whenever there is dependency in building the different modules of the software, then we use Spiral Model.
- whenever the customer gives the requirements in stages, we develop the product in stages.
3. V — MODEL / V & V MODEL (Verification and Validation Model )
This model came up in order to overcome the drawback of waterfall model — here testing starts from the requirement stage itself.
The V & V model is shown in the figure in the next page.
1) In the first stage, the client send the CRS both to developers and testers. The developers translate the CRS to the SRS.
The testers do the following tests on CRS, 1. Review CRS
a. conflicts in the requirements b. missing requirements
c. wrong requirements
2. Write Acceptance Test plan
3. Write Acceptance Test cases
The testing team reviews the CRS and identifies mistakes and defects and send it to the development team for correcting the bugs. The development updates the CRS and continues developing SRS simultaneously.
2 ) In the next stage, the SRS is sent to the testing team for review and the developers start building the HLD of the product. The testers do the following tests on SRS,
1. Review SRS against CRS
a. every CRS is converted to SRS
b. CRS not converted properly to SRS
2. Write System Test plan
3. Write System Test case
The testing team reviews every detail of the SRS if the CRS has been converted properly to SRS.
3 ) In the next stage, the developers start building the LLD of the product. The testers do the following tests on HLD,
a)Review HLD
b)Write Integration test plan
c)Write Integration test case
4) In the next stage, the developers start with the coding of the product. The testing team carries out the following tasks,
1. Review LLD
2. Write Functional test plan 3. Write Functional Test case
After coding, the developers themselves carry out unit testing or also known as white box testing. Here the developers check each and every line of code and if the code is correct. After white-box testing, the s/w product is sent to the testing team which tests the s/w product and carries out functional testing, integration testing, system testing and acceptance testing and finally deliver the product to the client.
Advantages of V&V model
1) Testing starts in very early stages of product development which avoids downward flow of defects
which in turn reduces lot of rework
2) Testing is involved in every stage of product development
3) Total investment is less — as there is no downward flow of defects. Thus there is less or no re-work
Drawbacks of V&V model
1) Initial investment is more — because right from the beginning testing team is needed
2) More documentation work — because of the test plans and test cases and all other documents Applications of V&V model
4. PROTOTYPE DEVELOPMENT MODEL
The requirements are collected from the client in a textual format. The prototype of the s/w product is developed. The prototype is just an image / picture of the required s/w product. The customer can look at the prototype and if he is not satisfied, then he can request more changes in the requirements.
Prototype testing means developers/ testers are checking if all the components mentioned are existing.
The difference b/w prototype testing and actual testing — in PTT, we are checking if all the components are existing, whereas, in ATT we check if all components are working.
Advantages of Prototype model
1) In the beginning itself, we set the expectation of the client.
2) There is clear communication b/w development team and client as to the requirements and the final outcome of the project
Drawbacks of Prototype model
1) There is delay in starting the real project
2) To improve the communication, there is an investment needed in building the prototype.
These are the different models available to develop software…