Sequential product development is a method of product design and development in which each stage of the process leads to the next without overlap. It is also known as a “waterfall” or “over the wall” method, because at the end of each stage, the design is metaphorically thrown over the wall or down a waterfall to the next design group in the process that will address their particular aspect of the product’s design.
The advantage of this methodology is that it enhances managerial control, however, the method has its drawbacks and many manufacturers have recognized the advantages of a more responsive, agile product development model. Product Time to Market Time-to-market is a major drawback to sequential product development methodology because each step in the sequence must be completed before the process can move forward. This wastes time when some elements can be designed concurrently. As an alternative, the concurrent engineering method groups major design elements for a maximum of overlap of activities so that different teams can work at the same time on multiple issues.
Lack of Client Collaboration Sequential product development does not allow for client or end-user collaboration. Product designers and developers consult the client only through a series of interviews and then proceed through the sequential process with a type of tunnel vision.
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This often results in client dissatisfaction and frustration. The Joint Application Development method, developed by Chuck Morris and Tony Crawford of IBM in the late 1970s, addressed this problem by beginning the design process with a succession of collaborative workshops called JAD sessions in which designers and clients work together on product design in a collaborative process. Brought to you by Rigid Design Process Sequential models have an assembly-line rigidity that tends to stifle design creativity by limiting the input of the different design groups to their particular stage in the sequence of development. Rapid Application Development models were designed to develop products more quickly in the conceptual stage, utilizing focus groups and workshops to make refinements to prototypes earlier in the development process. Lack of Flexibility Flexibility is severely limited in sequential product development because it is restricted to its linear organization. Flexibility in the development process enables designers to adapt to the marketplace during the development process.
The sync-and-stabilize method, developed by David Yoffie of Harvard University and Michael Cusumano of MIT, addressed the flexibility issue by allowing different teams to work in parallel on different aspects of product design while frequently synchronizing their work throughout the development process. Dealing With Complexity Sequential methods of product development can be inefficient in dealing with complex design issues. The product moves from one design group to the next until the final stage when a prototype is developed.
However, with complex designs, many prototypes are often required because prototypes must be tested and evaluated by multiple design groups. The spiral model was designed to address this issue. It uses a four-fold process: assess the strengths and weaknesses of a prototype; define requirements for the second prototype; refine the second prototype and finally, build and test the refined prototype. This allows complex design issues to be addressed as a whole.
Process models. 1.
1 Process Models Chapter 3. 2 A software life cycle is the series of identifiable stages that a software product undergoes during its lifetime. A software life cycle model is a descriptive and diagrammatic representation of the software life cycle.
A life cycle model represents all the activities required to make a software product transit through its life cycle phases. It also captures the order in which these activities are to be undertaken. Different life cycle models may map the basic development activities to phases in different ways.
3 Why do we require a life cycle model? The primary advantage is that it encourages development of software in a systematic and disciplined manner.
When a software product is developed by a team, it is necessary to have a precise understanding among the team members as to – when to do what. Otherwise it may lead to confusions and project failure. 4 The Waterfall Model Communicat ion Planning Modeling Const ruct ion Deployment analysis design code t est project init iat ion requirement gat hering estimating scheduling tracking delivery support f eedback. 5 1. Real project rarely follow sequential flow that the model proposes 2.
Linear model can accommodate iteration, it does indirectly 3. Can cause confusion as the project team proceeds. Difficult for the customer to state all requirement explicitly 5.
Customer must have patience 6. Linear nature of water flow leads to “blocking state” 7. Leads the team member to wait until previous member finishes 8. Time spent waiting is more compared with time spent for productive work 9. It is inappropriate 10. Requirement is fixed and proceed in linear manner. 6 Incremental Process Model analysis design code test System/information engineering analysis design code test analysis design code test analysis design code test increment 2 increment 3 increment 4 increment 1 delivery of 1st increment delivery of 2nd increment delivery of 3rd increment delivery of 4th increment calendar time.
7 Incremental Process Model Combines elements of the waterfall model applied in an iterative fashion. Incremental applies linear sequences as the calendar time progress. Limited software functionalities and expands functionalities in later software release. 8 Increment Model Each linear sequence produces a deliverable ‘increment’ of the software Eg.
Word processing software First increment is often a core product Basic requirements are addressed, but many supplementary remains undelivered. Customers evaluate this core product and the next increment is planned based on suggestions and next set of features The plan addresses the modification of core product and delivery of additional features and functionalities. Process is repeated until complete product is produced.
9 Increment Model Useful when Staff is unavailable for complete implementation and deadline is tight If core product is well received, additional staff can implement next increment Increment can be planned to manage technical risks Partial functionalities can be delivered to end – user without inordinate delay. 10 RAD Model Communication team #3 60 - 90 days Planning Modeling Construction Testing Modeling Construction team #1 team #2 Modeling Construction. 11 RAD Model Rapid Application Development Model It is incremental software development process. A short development cycle It is “high speed” adaptation of linear sequential model. Done by component based construction.
Requirements should be well understood and scope must be limited. Enables development team to create “fully functional” system with short time period. 12 RAD model Generic framework activities of RAD are: Communication: What information is required, who generates it, who processes it, where does it go etc. Planning: Multiple software team works in parallel on different functions. Process modeling: 3 modeling - Business modeling - Data modeling - process modeling Construction: Code generation Deployment: Is faster because of reusable components. 13 RAD model Advantages of RAD model 1.
Can be used for projects which can be modularized. Separate RAD teams can work on different modules.
Overall time requirement is very less. Problems or disadvantages 1. Large manpower required to create large number of RAD teams. Developers and customers must be committed to this type of model.
Fast responses are required from both the parties. Not useful for all types of systems i.e. If it is not possible to modularize. Not useful when technical risks are high i.e.
New software using new technology or new software has to work with existing hardware. 14 Prototype Model Customer defines objective to software engineer, but not specifies input, process,output requirements. Developer may be unsure about efficiency of algorithm, adaptability of OS, or human-machine interaction In this situation Prototype is best approach.
15 Evolutionary Process Model 1. These models are more suited to object oriented systems. They are iterative. They enable the software developer to develop increasingly more complex versions of the software 4.
Like all complex systems, software evolves over a period of time and hence evolutionary models are more suited to software development. Requirements change while software gets developed. 16 Prototype Model Used as standalone Process model Used in all technique implemented in any process model Prototype paradigm assists software and customer to better understand and build the software when requirement is fuzzy. 17 Prototype Model Quick Model Communication Development Delivery & Feedback Construction of Prototype Modeling Quick design.
18 Prototype Model 1. Communication - Software Engineer and customer defines overall objective - Identifies requirements and outline area - Definition is mandatory 2.
Concurrent Engineering Model
Quick plan is made 3. Quick design: A Prototype iteration is planned quickly and modeled 4. Design leads to constructing a prototype 5. Prototype deployed and delivered to end user Feedback is used to refine requirement for software Iteration occurs as the prototype is tuned to satisfy customers need and developers to better understand which needs to be done.
Concurrent Software Development
19 Prototype Model Limitations At the prototype level no focus on software quality or long-term maintainability In order to make the prototype working quickly, the developer often makes implementation compromises and becomes familiar with these choices. 20 Spiral Model Proposed by Boehm - Evolutionary software process model Couples Iterative nature of prototyping + waterfall model Potential for rapid development of increasingly more complete version of software Spiral Model - software is developed in a series of evolutionary releases.