Status of Bug

Status of Bug

       1>New

       2>Open

       3>Rejected

       4>Fixed

       5>Closed

Bug Life Cycle

BUG LIFE CYCLE

V-Model

V-MODEL

Ø  Just like the WFM, the V-shaped life cycle is a sequential path of execution of process

Ø  Each phase must be completed before the next phase begins.

Ø  Testing is emphasized in this model more.

Ø  The testing procedures are developed early in the life cycle before any coding is done, during each of the phases preceding implementation.

Ø  Requirements begin the life cycle just like the WFM. Before development is started, a system test plan is created. The test plan focuses on meeting the functionality specified in the requirements gathering.

Ø  The design phase focuses on system architecture & design. An integration test plan is created in this phase as well in order to test the piece of s/w systems ability to work together.

Ø  The low Level Design (Coding) phase is where the actual s/w component are designed & unit tests are created in this phase as well.

Ø  Once Coding is completed, the path of execution continues up the right side of the V, where the test plans developed earlier are now put to use.

ADVANTAGES

1)      Simple & easy to use.

2)      Each phase has specific deliverables.

3)      Higher chance of success over the WFM due to the development of test plans early on during the life cycle.

4)      Works well for small projects where requirements r easily understood.

     DISADVANTAGES

1)      Very rigid, like WFM(It needs lot of resources & money)

2)      S/W is developed during the implementation phase, so no early prototype of the s/w is produced.

3)      Model doesn’t provide a clear path problem found during testing phase.

4)      Little flexible & adjusting scope is difficult & expensive.

Spiral Model

SPIRAL MODEL

Ø  The Spiral Model is similar to the incremental model, with more emphasis placed on risk analysis.

Ø  In spiral Model, the angular component represents “PROGRESS” & the radial component represent “COST”.

Ø  Each cycle in the spiral begins with the identification of objectives for that cycle, the different alternatives that r possible for achieving the objectives & the constraint that exist.

Ø  Next Step in the cycle is to evaluate these different alternatives based on objectives & constraint, design for that cycle. The focus of evaluation in this step is based on the risk perception for the project. Risk reflects the chances that some of the objectives of the project may be not met.

Ø  The next step is to develop strategies that resolve uncertainties & risk. This step may involve activities such as benchmarking, simulation & prototyping.

Ø  Finally in 4^th quadrant we plan for the next cycle or module.

Ø  The spiral model works for development as well as enhancement projects.

ADVANTAGES

1)      High amt of risk analysis, so preferred for high risks projects.

2)      Good for large & mission critical projects.

3)      S/W is produced early in the s/w life cycle.

DISADVANTAGES

1)      Can be a costly model to use.

2)      Risk analysis requires specific expertise...

3)      Project’s success is highly dependent.

Evolutionary Model

ITERATIVE ENHANCEMENT or EVOLUTIONARY MODEL

Ø  This model counters the limitation of WFM that requirements be completely specified before the rest of the development can proceed & tries to combine the benefits of both prototyping & WFM.

Ø  One effective use of this type of model is for product development.

Ø  The s/w should be developed in increments, each increment adding some functional capability to the system until the full system is implemented.

Ø  At each step (iteration), extensions & design modification can be made.

Ø  Each iteration passes through the requirements, design, implementation & testing process.

Ø  A working version of s/w is produced during the first iteration, so u have working s/w early on during the s/w development life cycle.

Ø  Subsequent iterations build on the initial s/w produced during the first iteration.

Ø  First a version is released that contains some capability. Based on feedback from users & experience with this version, a list of additional desirable’s features & capabilities is generated. These features form the basis of enhancement of the s/w & are included in the next version.

The first version contains some core capabilities & then more are added to later versions.

ADVANTAGES

1)      Generates working s/w quickly & early during the s/w life cycle.

2)      More flexible –less costly to change scope & requirements.

3)      Easier to test & debug in each increments than testing entire system as in WFM.

4)      Easier to manage risk becoz risky pieces r identified & handled during its iterations.

5)      Each iteration is an easily managed milestone.

DISADVANTAGES

1)      In generating business contract- how will the cost of additional features be determined & negotiated, particularly becoz the client organization is likely to be tied to the original vendor who developed the first version.

2)      Problems may arise pertaining to system architecture becoz not all requirements are gathered up front for the entire s/w life cycle.

3)      Each phase of an iteration is rigid & do not overlap each other.

Prototyping Model

PROTOTYPING MODEL

Ø  The goal of a prototyping –based development process is to counter the limitation of WFM. Requirement frozen.

Ø  Instead of freezing the requirements before any design  or coding can proceed, a throwaway prototype is built to help understand the requirements. This prototype is developed based on the currently known requirements.

Ø  By using this prototype, the client can get an actual feel of the system, because the intraction with the prototype can enable the client to better understand the requirements of the desired system. This results in more stable requirements that change less frequently.

Ø  After the prototype has been developed, the end user & clients are given an opportunity to use the prototype & play with it.

Ø  Based on their experience, they provide feedback to the developers regarding the prototype: What is correct, what needs to be modified, what is missing, what is not needed.

Ø  Based on the feedback, the initial requirements are modified to produce the final requirements specification, which is then used to develop the production quality system.

ADVANTAGES

1)      It is well suited for projects where requirements are hard to determine & the confidence in obtained requirements is low.

2)      It is an excellent technique for reducing some types of risks associated with a project.

3)      By using COST CUTTING METHODS, it is possible to keep the cost of prototype less than a few percent of the total development cost. COST CUTTING METHODS-Minimal documentation, Reduce Testing.

            DISADVANTAGES

1)      Inferior, temporary design solutions may become  permanent after  a while, when  the developers has forgotten  that they were only intended to be temporary.(Result in poor software quality)

2)      Customer may object to prototyping being  thrown away & may demand “ a few changes” to make it working .(Result in poor s/w quality & maintainability)

3)      MINIMAL DOCUMENTATION may cause problem, in prototyping. Design doc, a test plan, a test case specification r not needed during the development of prototype. REDUCE TESTING cost cutting measures-but results in low quality product.

èPrototyping is often not used , as it is feared that development costs may become large. However, in some situations, the cost of s/w development without prototyping may be more than with prototyping. There r two major reason for that………..

a)      The experience of developing the prototyping might reduce the cost of the the later phases when the actual software development is done.

b)      In many projects the requirements are constantly changing, particularly when development takes a long time.

Waterfall Model

WATERFALL MODEL

Ø  WFM states that the phases are organized in a linear order. It is also referred as linear sequential life cycle model.

Ø  Each phase must be completed in its entirety, before the next phase can begin.

Ø  There r 2 assumptions made, when we work with WFM

v  For a successful project resulting in a successful product, all phases listed in WFM must be performed in anyways.

v  Any different ordering of the phases will result in a less successful software product.

Ø  In a typical model, a project begins with feasibility study. On successful demonstrating the feasibility of project, the requirements analysis & project planning begins. The design Starts after the requirements analysis is completed & coding begin after the design is completed. Once the programming is completed, the code is integrated & testing is done. On successful completion of testing, the system is installed. After this, the regular operations & maintenance of the system takes place.

Ø  When the activities of the phase r completed, there should be some product that is produced by the phase. The Goal of a phase is to produce this product. The o/ps of the earlier phases r often called WORK PRODUCTs (or intermediate products) & r usually in the form of documents like the requirement doc or design doc.

Ø  O/Ps of phases r-   
1>Requirement Doc
2>Project Plan
3>System Design Doc
4>Detailed Design Doc
5>Test plan & Test Reports
6>Final Code
7>Software manual(e.g. User, installation etc)

ADVANTAGES

1)      Simple & easy to use.

2)      Phases r processed & completed one at a time.

3)      Work well for smaller projects where requirements are very well understood.

4)      Easy to manage due to rigidity of Model-each phase has specific deliverables & a review process.

      DISADVANTAGES

1)      The requirements of the system can be frozen before the design begin, we can’t change SRS if design is done.

2)      Working s/w produced at the end of all phases so there is a long wait.

3)      High amt of risk & uncertainty.

4)      Poor Model where requirements r at a moderate –high risk of changing.

5)      Poor Model for long n ongoing projects.

6)      Poor Model for complex & Object oriented projects.