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System Develpment Methodologies

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sze wei yap

on 14 May 2013

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Transcript of System Develpment Methodologies

This methodology is often called the 'waterfall' method because each of the stages is completed before the next stage starts Waterfall Model Strengths Ideal for supporting less experienced project teams and project managers
The orderly sequence of development steps and strict controls of documentation and design reviews helps ensure the quality, reliability, and maintainability of the developed software.
Progress of system development is measurable.
Conserves resources. Weakness Inflexible, slow, costly and cumbersome due to significant structure and tight controls.
Project progresses forward, with only slight movement backward.
Depends upon early identification and specification of requirements, yet users may not be able to clearly define what they need early in the project.
Problems are often not discovered until system testing.
System performance cannot be tested until the system is almost fully coded
Difficult to respond to changes.
Produces excessive documentation and keeping it updated as the project progresses is time-consuming.
Written specifications are often difficult for users to read Situation most appropriate Project is large, expensive, and complicated. Project has clear objectives and solution.
Pressure does not exist for immediate implementation.
Project requirements can be stated unambiguously and comprehensively.
User community is fully knowledgeable in the business and application.
Team members may be inexperienced.
Project manager may not be fully experience
Resources need to be conserved.
Strict requirement exists for formal approvals at designated milestones Prototyping Model Prototyping Strengths Especially useful for resolving unclear objectives; developing and validating user requirements (
both performance and the human computer interface.) Potential exists for exploiting knowledge gained in an early iteration as later iterations are developed.
Helps to easily identify confusing or difficult functions and missing functionality
Encourages innovation and flexible designs.
Provides quick implementation of an incomplete but functional application
Improve user participation and communication Weakness Can lead to false expectations, where the customer mistakenly believes that the system is “finished” when in fact it is no
Requirements may frequently change significantly
Designers may prototype too quickly, without sufficient analysis resulting in inflexible design
Designers may neglect documentation, resulting in insufficient justification for the final product and inadequate records for the future.
Can lead to poorly designed systems
Can lead to false expectations, where the customer mistakenly believes that the system is “finished” when in fact it is no
Iterations add to project budgets and schedules, thus the added costs must be weighed against the potential benefits. Situation where most appropriate For online system requiring extensive user dialog
Project is large with many users, interrelationships and functions
Project objectives are unclear.
Pressure exists for immediate implementation of something
Functional requirements may change frequently
User is not fully knowledgeable.
Team members are experienced
Team composition is stable.
Project manager is experienced.
No strict requirement exists for approval Spiral Model Spiral Model Spiral model combines the features of the prototyping and the waterfall model. Strengths Enhances risk avoidance.
Useful in helping to select the best methodology to follow for development of a given software iteration based on project risk.
Can incorporate into waterfall, prototype
Challenging to determine the exact composition of development methodologies to use for each iteration around the Spiral.
Highly customized to each project,
Skilled project leader is required
There is no firm deadline
No control for moving from 1cycle to another, might results more work for the next cycle Weakness Real-time or safety-critical systems.
Risk avoidance is a high priority.
Minimizing resource consumption is not an absolute priority.
Project leader is highly skilled and experiences
Requirement exists for strong a approval
Project might benefit from a mix of different development methodologies
A high degree of accuracy is essential
Implementation has priority over functionality Situations where most appropriate Rapid Application Development Rapid Application Development The "planning" of software developed using RAD is interleaved with writing the software itself. Strengths
This produce application at a lower cost, money and labour
The operational version of an application is available much earlier
Greater level of commitments from end users
Concentrates on essential system elements from user viewpoint
Provides the ability to change system design as demanded by users
Produces a tighter fit between user requirements and system specifications Weakness More speed and lower cost may lead to lower overall system quality.
Danger of misalignment of developed system with the business due to missing information
Project might end up with more requirement
Potential for inconsistent designs within and across systems.
Potential for violation of programming standards
Difficulty with module reuse for future systems.
Potential for designed system to lack scalability.
High cost of commitments on key user personnel
Formal reviews and audits are more difficult Project is of small –to-medium scale and short duration
Project scope is focused
Application is highly interactive, has a clearly defined user group, and is not computationally complex
Users possess detailed knowledge of the application area
Requirements of the system are unknown or uncertain
Data for the project already exists
Development team is empowered to make design decisions on a day-to-day basis without the need for consultation with their superiors, Situation where most appropriate Conclusion Regardless of the development models, people, tasks, time table and cost must be managed Waterfall Model Rapid Application Development
RAD Spiral Model Prototyping Overview of System Development Methodologies Waterfall Project is divided into sequential phaseses
Deliverable and milestones to measure progress
Emphasis on planning of an entire system
Tight control is maintained through the use of written documentation Spiral Model Series of iterations based on user feedback
Final product gradually evolved
focus on risk assessment to minimize risks and speed up system development
requires intense interactivity between developers and end users
Each cycle must have specific goals that is accepted or rejected by users Rapid Application Development Fast development and delivery of high quality system at low cost
Breaking project into smaller segment and provide ease of change
fulfill the business need
Require active user involvement
Iteratively produces production software Prototyping Not a standalone methodology, but rather an approach to handling selected portion of a larger methodology (Spiral, RAD)
attempt to reduce rick by breaking project into smaller section
user involvement to increase the likelihood of user acceptance
small scale of system are developed following iteration until prototype evolved in final product
Understanding business problem is required A system development methodology refers to the framework that is used to structure, plan, and control the process of developing an information system.
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