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Lecture 05: Life Cycle Models - I — Transcript

by NPTEL IIT Kharagpur · 2,764 words · 444 segments · language en · Watch on YouTube

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0:01[Music]
0:17welcome to this lecture in the last
0:20lecture we discussed about the software
0:26development lifecycle in the software
0:31development like life cycle the project
0:34starting from the concept is developed
0:40by various activities the software
0:44development lifecycle essentially
0:46defines all the activities that are
0:49carried out and also the ordering among
0:51those activities there is an intuitive
0:56concept of the activities that are
1:00carried out during the software
1:01development but then as you will see
1:06that various project management life
1:09cycles structure these activities in
1:12different ways let's look at some
1:15popular life cycle models in this
1:19lecture we will discuss about the
1:21waterfall model we model evolutionary
1:25model and the prototyping model
1:31the lifecycle the project lifecycle is
1:34very important for the project manager
1:37because based on the lifecycle the
1:44project manager can track the progress
1:47of the project because there are various
1:50milestones in the lifecycle and as the
1:56milestones are met the project manager
1:59can tell how much progress has been
2:01achieved or at which stage the project
2:04is without a lifecycle model the project
2:12manager is handicapped it becomes very
2:16difficult for the project manager to
2:18monitor and control the project doesn't
2:22know that how much work is remaining and
2:27therefore the project gets delayed the
2:31cost rises and therefore for every
2:36non-trivial project the project manager
2:39uses a suitable lifecycle model and the
2:43development team follows it without a
2:49lifecycle model usually a problem it's
2:53known as the 99% complete syndrome
2:56occurs here the project manager has no
2:59way of finding out the progress of the
3:03project other than asking the team
3:05members that how are you doing how much
3:07you have completed typically the
3:11development team is very enthusiastic
3:16and they optimistically answer that we
3:20have almost done only a small thing is
3:21there and each time you ask them they
3:27say that see were nearly done so the
3:30project manager thinks that the project
3:33is about to complete but is far from
3:36true it takes many more months or years
3:41even when he
3:42I'm project manager here's the turn that
3:45the work is almost done and that is
3:49known as the 99% complete syndrome it
3:53occurs when the project manager has no
3:57other way to track the progress of the
3:59project other than asking for the
4:03opinion of the team members that how far
4:06they have progressed as you were
4:09discussing the project management
4:11lifecycle allows the project manager to
4:14have various milestones and stage
4:21completion by which the project manager
4:24can track the progress of the project
4:27more meaningfully another very basic
4:35concept that we will discuss before
4:38looking at the lifecycle models as the
4:43project progresses various deliverables
4:46are produced it is a myth if we say that
4:51the working program is the deliverable
4:55of a project not really there are a
4:58large number of deliverables that are
5:01produced as the project progresses and
5:03these are the documentation of all
5:06aspects of development for example
5:09specification design etcetera
5:17we'll discuss about the waterfall
5:19remodel evolutionary prototyping a
5:22spiral model this will call as the
5:24traditional model this have been used
5:27for traditional projects where the
5:31project is a product development project
5:34starting from scratch but for services
5:39type of projects typically the agile
5:43models are used we will first discuss
5:47about the traditional models the
5:50waterfall we model evolutionary
5:52prototyping spiral model we'll find out
5:56what are the shortcomings of these
5:57models why they are not so suitable for
6:01the services type of projects and we'll
6:10discuss about the agile model and we'll
6:13see that how they overcome those
6:14problems the software life cycle as we
6:19had already said in their series of
6:21stages during the development of the
6:24software intuitively every software has
6:31a feasibility study during which it is
6:36decided whether to take up this project
6:40or not the requirement analysis and
6:43specification design coding testing and
6:46maintenance so these are the stages that
6:51intuitively every software undergoes the
6:54feasibility study requirements analysis
6:56and specification design coding testing
6:59and maintenance the classical waterfall
7:04model fits very accurately to the
7:08intuitive model of software development
7:13here the activities are carried out one
7:18after other first the feasibility study
7:21is undertaken then requirements analysis
7:25and specification work is undertaken and
7:27once that is complete the design is
7:30taken then the coding and unit testing
7:32is undertaken next the integration and
7:36system testing is undertaken and finally
7:39the maintenance fades is undertaken this
7:43is a very close fit to the intuitive
7:46model of software development and this
7:51is called as the classical waterfall
7:53model because based on this model all
8:00other lifecycle models have been
8:02developed this is the classical model
8:04and all other models are derivatives of
8:07this model so this is according to the
8:11conceptual model of software development
8:14we were discussing life if we represent
8:16the classical waterfall model in a
8:19diagrammatic form we can see that the
8:25different phases are represented here
8:27feasibility study requirement analysis
8:30specification design coding testing and
8:32maintenance and there is a transition
8:37from one phase to the other if we look
8:41at it looks like a waterfall a series of
8:44waterfall and from this the named
8:50waterfall model comes
8:56this is the simplest and most intuitive
8:59model out of all the phases in the
9:07classical waterfall model which phase
9:10takes the most effort if we look at all
9:17the phases the phases between the
9:22feasibility study and testing are called
9:24as the development phases and then we
9:26have the maintenance phase is called
9:28development phases because here the
9:30product is developed and delivered to
9:33the customer and after that the
9:35maintenance phase starts among all the
9:38phases if we consider all the phases the
9:41development phases and maintenance phase
9:43then the maintenance phase consumes the
9:46maximum effort but among the development
9:49phases the testing phase consumes the
9:53maximum effort you may wonder that is it
9:59really the testing phase which consumes
10:01the maximum effort the answer is that
10:04see we are discussing about a commercial
10:07software it's not a student project a
10:10student project or a student assignment
10:15the student just takes that it is
10:18working for few inputs and then submits
10:20it whereas we are discussing about a
10:23commercial software where it has to be
10:27extensively tested the quality needs to
10:31be maintained because the organization's
10:33name is at stake you can't just give a
10:39software having bugs to the customers
10:41and therefore the testing phase consumes
10:45the maximum effort for every non-trivial
10:50commercial software if we represent the
10:55effort the form of a diagram the
10:59maintenance phase takes the maximum
11:01effort but then among all other phases
11:04the development phases the testing is
11:07the one
11:07takes most effort and then comes the
11:11coding design and the requirement
11:13specification most organizations they
11:19document the software lifecycle model
11:23they follow they're not only they
11:27identify all the phases and the
11:30activities that take place in the phases
11:32they also identify what are the outputs
11:36or the deliverables that are produced at
11:40the end of FX what are the entry and
11:43exit criteria for the fed's and what are
11:47the methodologies that are to be used
11:48for by the developers for various phases
11:55and this forms a process model document
11:59and is a important reference book for
12:02all the team members the classical
12:10waterfall model we were saying that it's
12:13a very intuitive model and other models
12:21are derivatives of this model and the
12:27development methodology that the
12:29organization uses during various phases
12:33these are all documented in the form of
12:36a process model book given to the
12:39developers and they must understand this
12:43well before they undertake the
12:45development activities the first
12:49activity in the waterfall model is the
12:53feasibility study here the project
12:57manager is responsible to carry out the
13:00feasibility study the project manager
13:03needs to identify whether the project is
13:08feasible so that it can be undertaken by
13:13the development team and there are three
13:16types of feasibility that the project
13:18manager is concerned
13:21there are three dimensions of
13:23feasibility or three types of
13:24feasibility that the project manager is
13:27concerned the first one is technical
13:29feasibility whether the development team
13:34has the competence and capability to
13:40undertake the project for this the
13:45project manager needs to understand
13:48various aspects of the development to be
13:53undertaken and then assess whether the
13:57team that he has that they can
14:00technically double complete this project
14:04another important dimension of the
14:07feasibility is the economic feasibility
14:10whether the budget that is that would be
14:13available would be profitable to carry
14:17out the project this is also called as
14:22the cost-benefit feasibility the third
14:26dimension is the scheduled feasibility
14:28that is the time that the project
14:32manager estimates for the project to
14:37complete whether the customer agrees to
14:41that time or the customer wants the
14:44project to be completed in two weeks and
14:46the project manager estimates that needs
14:50at least three months and then the
14:53project manager would say that this is
14:56not feasible schedule whites-only when
15:01all the three feasibilities are
15:03satisfied the project manager agrees to
15:06undertake the project in the economic
15:11feasibility the financial implications
15:15are considered whether it's Remini rated
15:19to carry out the work whether it is
15:21technically feasible schedule wise it is
15:24feasible and for this the project
15:27manager roughly understands what the
15:30customer wants to do what the customer
15:34one
15:34out of the software the data which would
15:38be input to the system the processing
15:40that needs on the data and the output
15:43that are to be generated and based on
15:46that the project manager identifies that
15:52how many developers need to work for
15:56what duration and based on death the
16:00project manager identifies the cost of
16:03developing the project and based on that
16:07the budget that the sponsor of the
16:12project or the customer provides the
16:18budget based on that the project manager
16:20finds out whether it will be financially
16:23worthwhile and based on the activities
16:27required as part of the project the
16:28project manager identifies whether it is
16:31technically feasible and the project
16:34manager roughly identifies the time it
16:36takes and based on that whether it would
16:40be feasible schedule wise just a case
16:47study to identify just to illustrate
16:49what the project manager needs to do to
16:53carry out the feasibility study because
16:57this is the important activity for the
16:59project manager to carry out the
17:03feasibility study for a project this is
17:08a special provision fund scheme for a
17:12coalfield
17:13limited coalfield limited is a coal
17:17mining company and mining being a risky
17:23profession in addition to the ordinary
17:28Provident Fund that are available to the
17:31miners the company proposes to have a
17:35special Provident Fund scheme and for
17:38this it has invited bids and the project
17:42managers the visitor company
17:45and understand what the company needs
17:49they find that the coalfield limited has
17:52number of employees exceeding 50,000
17:56majority of these employees are casual
17:59laborers and mining being a risky
18:02profession casualties are very high
18:06though there is a Provident Fund scheme
18:09but the settlement time is very high and
18:12there is a need for a special Provident
18:14Fund scheme where the fund can be
18:16disbursed immediately and here the
18:20manager first visits the main office of
18:22the company finds out what are the
18:25functionalities required from this
18:27software finds that there are various
18:32mine sites where the data will be input
18:36about the miners who are working for a
18:40specific day and the contribution they
18:43make for that day towards the special
18:46Provident Fund scheme so the project
18:50manager visits some mine sites finds out
18:53what data to be input how many data what
18:59format and so on and then suggests
19:05alternate solutions for example there
19:08may be local databases at the mine site
19:12and this will be periodically uploaded
19:17to the central database at the company's
19:20head office and based on that the
19:26settlement when there are claims for the
19:29special Provident Fund scheme this will
19:31be made but then in this the project
19:36manager finds that there will be a delay
19:38because instantly claims cannot be
19:43settled but the another solution may be
19:47that the local mine sites only upload
19:50the data and these are immediately
19:53updated on the mined side there are no
19:56local databases at the mines but the
19:59are just data entry stations where the
20:02data is immediately updated on the
20:08server at the main office of the company
20:14but then the problem here is that an
20:17extremely reliable communication link is
20:20required because it needs to instantly
20:23update the data and the main computer
20:26whereas the other option when there is a
20:29local database the communication link
20:33may not be so reliable because only once
20:36in a while the data at the main office
20:40is updated and the cost for these
20:43different solutions is worked out by the
20:46project manager and then discusses the
20:49coalfield
20:50officials which option would be suitable
20:54for them and what is the budget what is
20:58the cost for each one and the budget
21:00available based on that the project
21:02manager makes a go/no-go decision so
21:05this is the typical sequence of
21:07activities that occurs that the project
21:10manager understands what are the
21:16requirements main requirements for the
21:19software what are the alternate
21:22solutions that can be proposed to solve
21:26the functionalities that are required
21:30and what is the cost for each of these
21:33alternate functionalities what is the
21:36best solution
21:38among these alternate solutions and
21:40based on that whether it is financially
21:44feasible technically feasible and
21:47schedule-wise feasible is determined the
21:50project manager that's what we have just
21:55written down here that the project
21:57manager first develops an overall
22:02overall understanding of the problem
22:05formulates the different solution
22:07strategies and examines the alternate
22:10solutions in terms of the resource
22:12required
22:12the cost of development and development
22:14time and forms a cost-benefit analysis
22:20and based on this the project manager
22:25finds that it is feasible to carry out
22:29the project or I find that it is
22:31infeasible due to high cost resource
22:33constraint technical results or schedule
22:38prism the cost-benefit analysis is a
22:44important activity during the
22:46feasibility study here the project
22:50manager needs to identify all costs the
22:53cost can be development costs the setup
22:57cost operational cost and also identify
23:01all the benefits that would accrue for
23:06example the benefit may not only be the
23:09financial budget that it provides the
23:12company gets but also the experience it
23:19builds up the reusable software that it
23:22makes and so on at the end of the
23:27cost-benefit analysis the project
23:29manager needs to check whether the
23:31benefits are greater than the costs for
23:34the project to proceed so this is what I
23:41have just pictorially written here that
23:44the benefits are more than the costs
23:47then the project is undertaken the costs
23:50include development operation setup
23:52etcetera and the benefits some are
23:54quantifiable benefits like how much the
23:58customer is willing to pay but then
24:00there are non quantifiable benefits such
24:05as the experience reusable software and
24:10so on
24:14one of the important activity of the
24:17project manager is right to write the
24:19business case we had said that this is
24:24one of the initiating processes to write
24:27the business case the feasibility study
24:32once it is undertaken helps the manager
24:35to write the business case here the
24:40project manager provides a justification
24:42for starting the project and shows that
24:50the benefit of the project exceeds the
24:53cost and also identifies the business
24:58risks
25:20a business case is a very important
25:24document and writing a business case is
25:30an important project management process
25:34initiating process almost anybody
25:38aspiring to become a project manager
25:40needs to write a business case sometime
25:44or other here for writing a business
25:49case need to have an executive summary
25:52of what is required the project
25:56background the business opportunities
26:01that is what are the benefits that the
26:04project will bring what we will lose if
26:08we do not do the project what are
26:12various costs that will be incurred as
26:17the project progresses the benefits and
26:21what are the risks and how these risks
26:26will be managed
26:32the business case is submitted to the
26:34top management this gives them an
26:38overview of what is involved in the
26:41project how it will help the company and
26:47what are the costs and benefits and what
26:54will be the risks here and what are the
26:56plans of risk management this forms an
27:02important project initiation process
27:09with this discussion we'll just stop
27:12here and continue in the next lecture
27:16thank you

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