The General Model
Software life cycle models describe phases of the software cycle and the order in which those phases are executed. There are tons of models, and many companies adopt their own, but all have very similar patterns. The general, basic model is shown below:
Each phase produces deliverables required by the next phase in the life cycle. Requirements are translated into design. Code is produced during implementation that is driven by the design. Testing verifies the deliverable of the implementation phase against requirements.
Software life cycle models describe phases of the software cycle and the order in which those phases are executed. There are tons of models, and many companies adopt their own, but all have very similar patterns. The general, basic model is shown below:
Each phase produces deliverables required by the next phase in the life cycle. Requirements are translated into design. Code is produced during implementation that is driven by the design. Testing verifies the deliverable of the implementation phase against requirements.
Requirements
Business requirements are gathered in this phase. This phase is the main focus of the project managers and stake holders. Meetings with managers, stake holders and users are held in order to determine the requirements. Who is going to use the system? How will they use the system? What data should be input into the system? What data should be output by the system? These are general questions that get answered during a requirements gathering phase. This produces a nice big list of functionality that the system should provide, which describes functions the system should perform, business logic that processes data, what data is stored and used by the system, and how the user interface should work. The overall result is the system as a whole and how it performs, not how it is actually going to do it.
Design
The software system design is produced from the results of the requirements phase. Architects have the ball in their court during this phase and this is the phase in which their focus lies. This is where the details on how the system will work is produced. Architecture, including hardware and software, communication, software design (UML is produced here) are all part of the deliverables of a design phase.
Implementation
Code is produced from the deliverables of the design phase during implementation, and this is the longest phase of the software development life cycle. For a developer, this is the main focus of the life cycle because this is where the code is produced. Implementation my overlap with both the design and testing phases. Many tools exists (CASE tools) to actually automate the production of code using information gathered and produced during the design phase.
Testing
During testing, the implementation is tested against the requirements to make sure that the product is actually solving the needs addressed and gathered during the requirements phase. Unit tests and system/acceptance tests are done during this phase. Unit tests act on a specific component of the system, while system tests act on the system as a whole.
So in a nutshell, that is a very basic overview of the general software development life cycle model. Now let’s look into some of the traditional and widely used common life cycle models.
Waterfall
V-Shaped
Incremental
Spiral
Prototyping
Business requirements are gathered in this phase. This phase is the main focus of the project managers and stake holders. Meetings with managers, stake holders and users are held in order to determine the requirements. Who is going to use the system? How will they use the system? What data should be input into the system? What data should be output by the system? These are general questions that get answered during a requirements gathering phase. This produces a nice big list of functionality that the system should provide, which describes functions the system should perform, business logic that processes data, what data is stored and used by the system, and how the user interface should work. The overall result is the system as a whole and how it performs, not how it is actually going to do it.
Design
The software system design is produced from the results of the requirements phase. Architects have the ball in their court during this phase and this is the phase in which their focus lies. This is where the details on how the system will work is produced. Architecture, including hardware and software, communication, software design (UML is produced here) are all part of the deliverables of a design phase.
Implementation
Code is produced from the deliverables of the design phase during implementation, and this is the longest phase of the software development life cycle. For a developer, this is the main focus of the life cycle because this is where the code is produced. Implementation my overlap with both the design and testing phases. Many tools exists (CASE tools) to actually automate the production of code using information gathered and produced during the design phase.
Testing
During testing, the implementation is tested against the requirements to make sure that the product is actually solving the needs addressed and gathered during the requirements phase. Unit tests and system/acceptance tests are done during this phase. Unit tests act on a specific component of the system, while system tests act on the system as a whole.
So in a nutshell, that is a very basic overview of the general software development life cycle model. Now let’s look into some of the traditional and widely used common life cycle models.
Waterfall
V-Shaped
Incremental
Spiral
Prototyping
Waterfall
This is the most common and classic of life cycle models, also referred to as a linear-sequential life cycle model. It is very simple to understand and use. In a waterfall model, each phase must be completed in its entirety before the next phase can begin. At the end of each phase, a review takes place to determine if the project is on the right path and whether or not to continue or discard the project. Unlike what I mentioned in the general model, phases do not overlap in a waterfall model.
Advantages
Simple and easy to use.
Easy to manage due to the rigidity of the model – each phase has specific deliverables and a review process.
Phases are processed and completed one at a time.
Works well for smaller projects where requirements are very well understood.
Disadvantages
Adjusting scope during the life cycle can kill a project
No working software is produced until late during the life cycle.
High amounts of risk and uncertainty.
Poor model for complex and object-oriented projects.
Poor model for long and ongoing projects.
Poor model where requirements are at a moderate to high risk of changing.
V-Shaped Model
Just like the waterfall model, the V-Shaped life cycle is a sequential path of execution of processes. Each phase must be completed before the next phase begins. Testing is emphasized in this model more so than the waterfall model though. The testing procedures are developed early in the life cycle before any coding is done, during each of the phases preceding implementation.
Requirements begin the life cycle model just like the waterfall model. Before development is started, a system test plan is created. The test plan focuses on meeting the functionality specified in the requirements gathering.
The high-level design phase focuses on system architecture and design. An integration test plan is created in this phase as well in order to test the pieces of the software systems ability to work together.
The low-level design phase is where the actual software components are designed, and unit tests are created in this phase as well.
The implementation phase is, again, where all coding takes place. Once coding is complete, the path of execution continues up the right side of the V where the test plans developed earlier are now put to use.
Advantages
Simple and easy to use.
Each phase has specific deliverables.
Higher chance of success over the waterfall model due to the development of test plans early on during the life cycle.
Works well for small projects where requirements are easily understood.
Disadvantages
Very rigid, like the waterfall model.
Little flexibility and adjusting scope is difficult and expensive.
Software is developed during the implementation phase, so no early prototypes of the software are produced.
Model doesn’t provide a clear path for problems found during testing phases.
Incremental Model
The incremental model is an intuitive approach to the waterfall model. Multiple development cycles take place here, making the life cycle a “multi-waterfall” cycle. Cycles are divided up into smaller, more easily managed iterations. Each iteration passes through the requirements, design, implementation and testing phases.
A working version of software is produced during the first iteration, so you have working software early on during the software life cycle. Subsequent iterations build on the initial software produced during the first iteration.
Advantages
Generates working software quickly and early during the software life cycle.
More flexible – less costly to change scope and requirements.
Easier to test and debug during a smaller iteration.
Easier to manage risk because risky pieces are identified and handled during its iteration.
Each iteration is an easily managed milestone.
Disadvantages
Each phase of an iteration is rigid and do not overlap each other.
Problems may arise pertaining to system architecture because not all requirements are gathered up front for the entire software life cycle.
Spiral Model
This is the most common and classic of life cycle models, also referred to as a linear-sequential life cycle model. It is very simple to understand and use. In a waterfall model, each phase must be completed in its entirety before the next phase can begin. At the end of each phase, a review takes place to determine if the project is on the right path and whether or not to continue or discard the project. Unlike what I mentioned in the general model, phases do not overlap in a waterfall model.
Advantages
Simple and easy to use.
Easy to manage due to the rigidity of the model – each phase has specific deliverables and a review process.
Phases are processed and completed one at a time.
Works well for smaller projects where requirements are very well understood.
Disadvantages
Adjusting scope during the life cycle can kill a project
No working software is produced until late during the life cycle.
High amounts of risk and uncertainty.
Poor model for complex and object-oriented projects.
Poor model for long and ongoing projects.
Poor model where requirements are at a moderate to high risk of changing.
V-Shaped Model
Just like the waterfall model, the V-Shaped life cycle is a sequential path of execution of processes. Each phase must be completed before the next phase begins. Testing is emphasized in this model more so than the waterfall model though. The testing procedures are developed early in the life cycle before any coding is done, during each of the phases preceding implementation.
Requirements begin the life cycle model just like the waterfall model. Before development is started, a system test plan is created. The test plan focuses on meeting the functionality specified in the requirements gathering.
The high-level design phase focuses on system architecture and design. An integration test plan is created in this phase as well in order to test the pieces of the software systems ability to work together.
The low-level design phase is where the actual software components are designed, and unit tests are created in this phase as well.
The implementation phase is, again, where all coding takes place. Once coding is complete, the path of execution continues up the right side of the V where the test plans developed earlier are now put to use.
Advantages
Simple and easy to use.
Each phase has specific deliverables.
Higher chance of success over the waterfall model due to the development of test plans early on during the life cycle.
Works well for small projects where requirements are easily understood.
Disadvantages
Very rigid, like the waterfall model.
Little flexibility and adjusting scope is difficult and expensive.
Software is developed during the implementation phase, so no early prototypes of the software are produced.
Model doesn’t provide a clear path for problems found during testing phases.
Incremental Model
The incremental model is an intuitive approach to the waterfall model. Multiple development cycles take place here, making the life cycle a “multi-waterfall” cycle. Cycles are divided up into smaller, more easily managed iterations. Each iteration passes through the requirements, design, implementation and testing phases.
A working version of software is produced during the first iteration, so you have working software early on during the software life cycle. Subsequent iterations build on the initial software produced during the first iteration.
Advantages
Generates working software quickly and early during the software life cycle.
More flexible – less costly to change scope and requirements.
Easier to test and debug during a smaller iteration.
Easier to manage risk because risky pieces are identified and handled during its iteration.
Each iteration is an easily managed milestone.
Disadvantages
Each phase of an iteration is rigid and do not overlap each other.
Problems may arise pertaining to system architecture because not all requirements are gathered up front for the entire software life cycle.
Spiral Model
The spiral model is similar to the incremental model, with more emphases placed on risk analysis. The spiral model has four phases: Planning, Risk Analysis, Engineering and Evaluation. A software project repeatedly passes through these phases in iterations (called Spirals in this model). The baseline spiral, starting in the planning phase, requirements are gathered and risk is assessed. Each subsequent spirals builds on the baseline spiral.
Requirements are gathered during the planning phase. In the risk analysis phase, a process is undertaken to identify risk and alternate solutions. A prototype is produced at the end of the risk analysis phase.
Software is produced in the engineering phase, along with testing at the end of the phase. The evaluation phase allows the customer to evaluate the output of the project to date before the project continues to the next spiral.
In the spiral model, the angular component represents progress, and the radius of the spiral represents cost.
Advantages
High amount of risk analysis.
Good for large and mission-critical projects.
Software is produced early in the software life cycle.
Disadvantages
Can be a costly model to use.
Risk analysis requires highly specific expertise.
Project’s success is highly dependent on the risk analysis phase.
Doesn’t work well for smaller projects.
Prototyping Model
Prototyping uses multiple iterations of requirements gathering and analysis, design and prototype development. After each iteration, the result is analyzed by the customer. Their response creates the next level of requirements and defines the next iteration.
There are several steps in the Prototyping Model:
The new system requirements are defined in as much detail as possible. This usually involves interviewing a number of users representing all the departments or aspects of the existing system.
A preliminary design is created for the new system.
A first prototype of the new system is constructed from the preliminary design. This is usually a scaled-down system, and represents an approximation of the characteristics of the final product.
The users thoroughly evaluate the first prototype, noting its strengths and weaknesses, what needs to be added, and what should to be removed. The developer collects and analyzes the remarks from the users.
The first prototype is modified, based on the comments supplied by the users, and a second prototype of the new system is constructed.
The second prototype is evaluated in the same manner as was the first prototype.
The preceding steps are iterated as many times as necessary, until the users are satisfied that the prototype represents the final product desired.
The final system is constructed, based on the final prototype.
The final system is thoroughly evaluated and tested. Routine maintenance is carried out on a continuing basis to prevent large-scale failures and to minimize downtime.
Advantages
Customers can see steady progress.
This is useful when requirements are changing rapidly, when the customer is reluctant to commit to a set of requirements, or when no one fully understands the application area.
Disadvantages
It is impossible to know at the outset of the project how long it will take.
There is no way to know the number of iterations that will be required.
System Investigation
Preliminary Investigation
The main objective of Preliminary Investigation is to identify the problem and the need for the new system.
Introduction to the existing system of the University
The University offers many numbers of programmes to the student. And for these programmes no of student who visit the University to find out the programmes on offer and requesting the staff to let them know about their eligibility to a particular programme(s). Until now all the operations are done manually. This means there is no appropriate system to handle all the student eligibility activity for a particular programe(s) in the University.
How the existing system work
If a student wants to find out the programmes on offer and requesting the staff to let them know about their eligibility to a particular programme, the staff performs the following tasks frequently.
Ask the qualification of the student.
Ask the programme in which the student is interested to take admission.
Find the requisite qualification for admission to the programme.
If the student’s qualification is same as requisite qualification for admission to the programme, then he informs the same to the student.
In case the student is not eligible, he informs the student about the qualification required.
Context diagram of the current system
Admission
Eligibility
Student
Staff
Programme and
Required qualification
Problem statement of the existing manual system
By doing an overall analyze the current manual system, we found out the problems and difficulties which are facing in this University. We interviewed staff and student in concern in this matter. The interview and the minutes will be on the appendix division. To solve these problems the management has decided to make it computerize and work with a user friendly environment.
The problem we found out is:
Checking the eligibility of a Student to different programs in a University is currently being handled manually by the staff at the University. The number of programs on offer by the University has been increasing every term as well as the number of interested student candidates, so checking the eligibility manually is becoming difficult and unreliable.
By studying the overall problems the current system of the University is facing, we find that our proposed system must be feasible enough to use by all the users. Also the system should be user friendly to use. The reason is looking forward for a student eligibility system is because of the above reasons.
In this part we will be doing a feasible study of our proposed system for the university giving a brief introduction about University student eligibility system. This method is used to determine whether the proposed solution is practical enough to implement. The study will include the feasibility in operational, economical. The study also includes the cost benefit of the proposed system.
Operational Feasibility
Operational feasibility is an evaluation to determine whether the system is operationally acceptable. In order to do that operational feasibility covers two aspects. One is a technical performance aspect and the other is the acceptance within the University. We have answered the essential questions that help the in testing the operational feasibility of a system.
Does the management support the project?
Requirements are gathered during the planning phase. In the risk analysis phase, a process is undertaken to identify risk and alternate solutions. A prototype is produced at the end of the risk analysis phase.
Software is produced in the engineering phase, along with testing at the end of the phase. The evaluation phase allows the customer to evaluate the output of the project to date before the project continues to the next spiral.
In the spiral model, the angular component represents progress, and the radius of the spiral represents cost.
Advantages
High amount of risk analysis.
Good for large and mission-critical projects.
Software is produced early in the software life cycle.
Disadvantages
Can be a costly model to use.
Risk analysis requires highly specific expertise.
Project’s success is highly dependent on the risk analysis phase.
Doesn’t work well for smaller projects.
Prototyping Model
Prototyping uses multiple iterations of requirements gathering and analysis, design and prototype development. After each iteration, the result is analyzed by the customer. Their response creates the next level of requirements and defines the next iteration.
There are several steps in the Prototyping Model:
The new system requirements are defined in as much detail as possible. This usually involves interviewing a number of users representing all the departments or aspects of the existing system.
A preliminary design is created for the new system.
A first prototype of the new system is constructed from the preliminary design. This is usually a scaled-down system, and represents an approximation of the characteristics of the final product.
The users thoroughly evaluate the first prototype, noting its strengths and weaknesses, what needs to be added, and what should to be removed. The developer collects and analyzes the remarks from the users.
The first prototype is modified, based on the comments supplied by the users, and a second prototype of the new system is constructed.
The second prototype is evaluated in the same manner as was the first prototype.
The preceding steps are iterated as many times as necessary, until the users are satisfied that the prototype represents the final product desired.
The final system is constructed, based on the final prototype.
The final system is thoroughly evaluated and tested. Routine maintenance is carried out on a continuing basis to prevent large-scale failures and to minimize downtime.
Advantages
Customers can see steady progress.
This is useful when requirements are changing rapidly, when the customer is reluctant to commit to a set of requirements, or when no one fully understands the application area.
Disadvantages
It is impossible to know at the outset of the project how long it will take.
There is no way to know the number of iterations that will be required.
System Investigation
Preliminary Investigation
The main objective of Preliminary Investigation is to identify the problem and the need for the new system.
Introduction to the existing system of the University
The University offers many numbers of programmes to the student. And for these programmes no of student who visit the University to find out the programmes on offer and requesting the staff to let them know about their eligibility to a particular programme(s). Until now all the operations are done manually. This means there is no appropriate system to handle all the student eligibility activity for a particular programe(s) in the University.
How the existing system work
If a student wants to find out the programmes on offer and requesting the staff to let them know about their eligibility to a particular programme, the staff performs the following tasks frequently.
Ask the qualification of the student.
Ask the programme in which the student is interested to take admission.
Find the requisite qualification for admission to the programme.
If the student’s qualification is same as requisite qualification for admission to the programme, then he informs the same to the student.
In case the student is not eligible, he informs the student about the qualification required.
Context diagram of the current system
Admission
Eligibility
Student
Staff
Programme and
Required qualification
Problem statement of the existing manual system
By doing an overall analyze the current manual system, we found out the problems and difficulties which are facing in this University. We interviewed staff and student in concern in this matter. The interview and the minutes will be on the appendix division. To solve these problems the management has decided to make it computerize and work with a user friendly environment.
The problem we found out is:
Checking the eligibility of a Student to different programs in a University is currently being handled manually by the staff at the University. The number of programs on offer by the University has been increasing every term as well as the number of interested student candidates, so checking the eligibility manually is becoming difficult and unreliable.
By studying the overall problems the current system of the University is facing, we find that our proposed system must be feasible enough to use by all the users. Also the system should be user friendly to use. The reason is looking forward for a student eligibility system is because of the above reasons.
In this part we will be doing a feasible study of our proposed system for the university giving a brief introduction about University student eligibility system. This method is used to determine whether the proposed solution is practical enough to implement. The study will include the feasibility in operational, economical. The study also includes the cost benefit of the proposed system.
Operational Feasibility
Operational feasibility is an evaluation to determine whether the system is operationally acceptable. In order to do that operational feasibility covers two aspects. One is a technical performance aspect and the other is the acceptance within the University. We have answered the essential questions that help the in testing the operational feasibility of a system.
Does the management support the project?
From the initial development of this system we have studied, conducted interviews, and many more analysis on how this should interact with the users mainly for the staff and we consistently informed the staff and requested for their feedback and altered our development process in order to satisfy the requirement in each an every development stage. And we have conducted tests using the Prototype version and we have the fully support for this design from the staff as well the student.
How do you know that this system will benefit the University?
How do you know that this system will benefit the University?
Yes. With compared to the earlier manual system the efficiency of the new system is very high and most of the manual operations such as Student Record keeping, searching for records, report making has automated. There for worked load of the staff is gone down. And University needs only few staff and they will be very efficient with the new system and some operations like searching a student record book and student details can be done by the staff. For the University the cost of paper, storing space and time can be saved with this new system.
Will the student effect in a considerable way?
Will the student effect in a considerable way?
Yes. As I mentioned earlier they can search required information much efficiently and some information like programme on offer, And student can get the information that is updated real time. Also staff can get a report of eligible student.
Economic Feasibility
Economic feasibly is an evaluation to determine whether a system is economically acceptable. For the University is an Investment so the management is looking forward to get an Idea about the Benefits and Risk and most importantly investing this system is worth. In order to answer this question we did a Cost Benefit analysis.
Recommended Hardware for the Proposed System
Pentium 2.0 GHz processor.
256MB of RAM.
Hard disk of 40GB or more.
Network card.
Video adapter monitor with VGA resolution.
CD-ROM drive.
3.5 inch disk drive.
Keyboard and Mouse.
AppServ (Soft wares- Apache web server, PHP, MySQL, phpMyAdmin-2.)
Functional Requirements
Functional requirements are the functions that the system is required to perform and they define the behavior of the Software.
They can be split up as follows.
View all the Programs on Offer.
Specify student qualification.
Select a desired program.
Check eligibility for Admission.
If yes: Inform the student about his admission and store his details in database for future reference.
If no: Inform the student about the required qualification for that programme.
Functional and Data modeling
Functional Modeling is an approach used to model any man-made system by identifying the designer defined overall goal it must achieve and the designer/user defined functions it must perform. A fully satisfactory description of such a system requires in fact answering to three questions in an explicit and unambiguous manner. The first question is:
Why was the system designed in the first place?
The answer to this question clarifies the intention(s) of the designer of the system and hence the overall goal the system must achieve. The answer leads us also to the second question:
What is the system supposed to do in order to achieve the goal?
The answer to this question clarifies the functions the system must perform, and it at the same time leads us to the third question:
How must different parts of the system's physical structure interact in order to realize the functions?
The answer to this question clarifies the behaviors of the physical structure, i.e., variable-interactions and interrelations and component-interconnections.
Thus, any man made system can be fully described by:
identifying its overall goal, its functions to achieve the goal, and
its physical structure's behaviors to realize those functions; and
doing this in the order given by the questions!
Classical modeling methods aim only to explain the behaviors of the physical structure, which also happens to be the answer to the last question! Therefore, the models generated by those methods are not true representation of their corresponding systems. Functional Modeling approach has on the contrary the objective of providing answers to the first two questions. This means also that the approach can assist one how to model the behaviors of a system's physical structure, or in other words, how to apply classical modeling methods in a systematic way.
Economic Feasibility
Economic feasibly is an evaluation to determine whether a system is economically acceptable. For the University is an Investment so the management is looking forward to get an Idea about the Benefits and Risk and most importantly investing this system is worth. In order to answer this question we did a Cost Benefit analysis.
Recommended Hardware for the Proposed System
Pentium 2.0 GHz processor.
256MB of RAM.
Hard disk of 40GB or more.
Network card.
Video adapter monitor with VGA resolution.
CD-ROM drive.
3.5 inch disk drive.
Keyboard and Mouse.
AppServ (Soft wares- Apache web server, PHP, MySQL, phpMyAdmin-2.)
Functional Requirements
Functional requirements are the functions that the system is required to perform and they define the behavior of the Software.
They can be split up as follows.
View all the Programs on Offer.
Specify student qualification.
Select a desired program.
Check eligibility for Admission.
If yes: Inform the student about his admission and store his details in database for future reference.
If no: Inform the student about the required qualification for that programme.
Functional and Data modeling
Functional Modeling is an approach used to model any man-made system by identifying the designer defined overall goal it must achieve and the designer/user defined functions it must perform. A fully satisfactory description of such a system requires in fact answering to three questions in an explicit and unambiguous manner. The first question is:
Why was the system designed in the first place?
The answer to this question clarifies the intention(s) of the designer of the system and hence the overall goal the system must achieve. The answer leads us also to the second question:
What is the system supposed to do in order to achieve the goal?
The answer to this question clarifies the functions the system must perform, and it at the same time leads us to the third question:
How must different parts of the system's physical structure interact in order to realize the functions?
The answer to this question clarifies the behaviors of the physical structure, i.e., variable-interactions and interrelations and component-interconnections.
Thus, any man made system can be fully described by:
identifying its overall goal, its functions to achieve the goal, and
its physical structure's behaviors to realize those functions; and
doing this in the order given by the questions!
Classical modeling methods aim only to explain the behaviors of the physical structure, which also happens to be the answer to the last question! Therefore, the models generated by those methods are not true representation of their corresponding systems. Functional Modeling approach has on the contrary the objective of providing answers to the first two questions. This means also that the approach can assist one how to model the behaviors of a system's physical structure, or in other words, how to apply classical modeling methods in a systematic way.
