Old and new SDLC models

Old SDLC (Software Development Life Cycle) Models:

a) Waterfall model or Linear sequential model
b)Prototype model
c) Incremental model
d)Spiral model
e) Rapid application development (RAD) model 

Before learning the waterfall model let you know about:
Software bidding:A proposal to develop a new software is called as 'software bidding'

• If a proposal came from the customer point of view then it is called as "software project bidding".
• If a company will study the needs of the market and develop the software then that type of proposal is called as "software product bidding"

a) Waterfall Model:
                                       

                                          

                                              Fig: Waterfall Model

Note: The above waterfall model is also called as the "Linear Sequential Model"
Explanation of above diagram:

1. From the above diagram at first software bidding will be done between the CEO of company and customer or client. Then after bidding, the CEO will conduct the meeting with all the project managers(PM) in the company called as "kick of meeting"(KIM). 
2. In that meeting  CEO will make an announcement about that new project to handle that project any one of the project manager will be selected.Then that project manager will give an project initiation note(PIN) to CEO.
3.  Then PM will assign the work to the business analyst(BA) to gather all the requirements from the customer.
4. Then BA will submit all the gathered requirements to the system analyst(SA) to design inorder to do the analysis or detailed planning which is going to submit it to the PM.Then PM will approve that planning done by SA. 
5. Then SA will submit that document to the technical architect(TA). 
6. Then designers will do the design which consists of HLD and LLD's.
7. Based on that design programmers will do the coding and that corresponding programmers will test the developed code. 
8. Then after testing that  s/w few programmers will be selected for onsite and release the s/w. 
9. Then change for control board(CCB) people will do the maintenance/support of that s/w.                 

b) Prototype Model: 
Whenever the customer requirements are not clear, organizations can goto develop a model software to show to customers and to get clear requirements.This sample software is called as "prototype".
                                                     

                                         

                                           
                                           Fig: Prototype model
Explanation of above diagram:

1. From the above diagram at first software bidding will be done between the CEO of company and customer or client. Then after bidding, the CEO will conduct the meeting with all the project managers(PM) in the company called as "kick of meeting"(KIM).
2.  In that meeting  CEO will make an announcement about that new project, to handle that project any one of the project manager will be selected.Then that project manager will give an project initiation note(PIN) to CEO. 
3. Then PM will assign the work to the business analyst(BA) to gather all the requirements from the customer.If customer requirements are not clear then company will develop a model s/w and show to the customer. At that time customer will identify the new requirements and those requirements will be gathered by BA.
4. Then BA will submit all the gathered requirements to the system analyst (SA) inorder to do the analysis or detailed planning which is going to submit it to the PM.Then PM will approve that planning done by SA. 
5. Then SA will submit that document to the technical architect(TA). 
6. Then designers will do the design which consists of HLD and LLD's.
7. Based on that design, programmers will do the coding and that corresponding programmers will test the developed code. 
8. Then after testing that  s/w, few programmers will be selected for onsite and release the s/w. Then change for control board(CCB) people will do the maintenance/support of that s/w.

c) Incremental Model: 
When customer requirements are clear but, huge.Then the organizations can follow the incremental model to release the  software installment by installment.

Fig: Incremental model

1. From the above diagram in the first installment (i #1) all the process from the software requirement gathering(SRG) to maintenance will be done and this will be proceeded  upto last installment (i # N). 
2. Thus finally all the huge requirement software will be developed and released to the customer installment by installment.

d) Spiral Model:
When the requirements are clear and enhancing regularly, organizations can follow spiral model to release the software version by version.

                                                                Fig: Spiral Model

1. From the above diagram requirement gathering will be done at first and later design this will be continued till the maintenance stage.
2. If customer will need any enhancements, those enhancements will be gathered by them and again with the new requirements, analysis will be done. This cycle will be repeated for every new version of the software.

e) Rapid Application Development (RAD) Model:

1. Organizations are following this Model, when Customer Requirements are known.
    
2. When customer requirements are similar to old projects, then organizations can follow this model to develop a new software by copying coding from old projects and they will r
   elease new Software using existing Software Coding.
3.  Here, New Software will be integrated by using Existing Components of Old Projects

Advanced SDLC (Software Development Life Cycle) Models:

Before going to learn the Advanced SDLC models, let you know the reasons for 
outdating the old SDLC models in the organizations.They are:
1. In all the Old SDLC Models, Testing Stage comes after Coding only.
2. This Single Stage of Testing is conducted by the Same Programmers / Developers who perform Coding.
3. Due to this, Organizations are not able to release Quality Software to Customer or to Market.
4. To Develop and Release Quality Software, Organizations are following New SDLC Models.
5. In New SDLC Models, Organizations conduct Multiple Stages of Testing and maintain Separate Testing Teams. The new SDLC models are as follows:

a) Fish Model
b) V-Model
c) Agile Model(XP,SPRINT,SCRUM)

a) Fish Model:

To develop a quality s/w w.r.t to customer requirements and expectations,organizations  are following fish model.But, this model is costly to follow
and time consuming model.

Explanation of above diagram:

                                                                     Fig: Fish Model

1. At first project initiation note(PIN) will be given to the CEO,from there the work is going to begin.
2. The business analyst(BA) will gather all the requirements from the customer and for that gathered requirements testing purpose a 'seperate testing team' will be assigned.
3. Then system analyst(SA) will do the analysis of that requirements and for the review of those analysed requirements a 'seperate testing team' will be assigned.
4. Technical architect (s.r programmer) will do the design of those analysed requirements in the form of HLD and LLD's after that a 'seperate testing team' will be assigned for the review of those design. 
5. All the above conducted testing or reviewing is called as 'documents testing' or 'verification' or 'static testing'.
6. Unit testing: unit testing means that conducting testing on a single programme in java, .NET,oracle,SAP,C,C++ and etc.
7. Integration testing: Integration testing means conducting testing on the interconnection of two or more programmes.The below diagram depicts the integration testing: 

8.       Software testing: software testing means conducting the testing on a complete   

          software w.r.t to the customer requirements and expectations.

9.      Acceptance testing: Acceptance testing means that collecting the feedback on 

         s/w from the real customers(Clients) or model customers(Public).

10.     Release testing: Release testing means that the whether s/w was completely and          

           correctly ported into customer site or not. It is also called as onsite testing/

           delivery testing/port testing.

11.    Maintenance testing: During the maintenance testing, CCB people can modify 

         and test s/w w.r.t to customer change request.        

b) V-Model: 

• This model was introduced by "William evans ferrie".
• 'V' stands for verification and validation.
• This model is also defining mapping in between development stages and testing stages.
• This model is not taking more time to develop a quality s/w unlike  Fish model.

                                                                 Fig: V-Model

Explanation of above diagram:

1. From the above model BA can prepare and review BRS.
2. SA can prepare and review SRS.
3. TA can prepare and review HLD and LLD's.
4. Programmer can write programmes and conduct unit testing and integration testing w.r.t  LLD's and integration testing w.r.t HLD.
5. A seperate testing team can test s/w (system testing) w.r.t SRS.
6. Customer site people can provide feedback on s/w w.r.t BRS.
7. Release team will take care of s/w release and port testing and CCB people can take care of maintenance/support.

Note: From the V-model, a separate test engineers will be needed for s/w testing stage.Those test engineers also responsible for involve in the acceptance testing and release testing.

Note: Small and medium scale companies prefer V-model to follow because this model is inexpensive and not taking more time.

c) Agile Model: In large scale companies,this model is followable.Because, client is able to maintain stakeholder team to approve deliverables of each stage in development.

After completion of software testing and approval from the stakeholders, real customers are involving to give the feedback on that software.
Under the guidence of stakeholders,release  team can release software and CCB can maintain software.
In agile model development stages will be called with different names:

Note: In old SDLC models, testing will come after coding only. But, in advanced SDLC models testing will come in every stage of develoment by same developer or seperate tester.
Old SDLC models with V-Model: 
 Prototype V-Model:

• When customer requirements are clear, organizations are following v-model by conducting testing in every stage of development and seperate testing team for software testing stage.
• When customer requirements are not clear, organizations will follow prototype   V-model.

• Once requirements are finalized, again same V-model will proceeds.  

Incremental V-Model:

When customer requirements are clear and huge, oraganizations can follow Incremental V-model.

Spiral V-Model: 

When customer requirements are enhancing regularly, oraganizations can follow Spiral V-model.

Case Study:(Old SDLC under along with Agile Model)

When customer requirements are clear and customers are ready to provide stakeholders then organizations can follow the 'Agile model'.

1. When customer requirements are not clear and customer is ready to provide stakeholders,organizations can follow prototype based agile model called as 'XP' (Extreame Programming).
2. When customer requirements are huge and customer is ready to provide stakeholders,organizations can follow in based incremental based agile model called as 'SPRINT'.
3. When customer requirements are enhancing regularly and customer is ready to provide stakeholders,organizations can follow spiral based agile model called as 'SCRUM'.