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Approaches to system development

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• Systems Development Life Cycle• Phases and Activities in the SDLC • Variations of the SDLC models

Lecturer details

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SDLC Provides overall framework for managing systems development processTwo main approaches to SDLC• Predictive approach – assumes project can be planned out in advance• Adaptive approach – more flexible, assumes project cannot be planned out in advance

System development life cycle (SDLC)

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• Project planning – initiate, ensure feasibility, plan schedule, obtain approval for project• Analysis – understand business needs and processing requirements• Design – define solution system based on requirements and analysis decisions• Implementation – construct, test, train users, and install new system• Support – keep system running and improve

Stages of SDLC

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• Define business problem and scope • Produce detailed project schedule • Confirm project feasibility / - Economic, organizational, technical, resource, and schedule • Staff the project (resource management) • Launch project official announcement---------------------------------------------------------------------------------

• Gather information to learn problem domain• Define system requirements• Build prototypes for discovery of requirements• Prioritize requirements• Generate and evaluate alternatives• Review recommendations with management

Stage 1&2: Project planning/Analysis

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• Design and integrate the network• Design the application architecture• Design the user interfaces• Design the system interfaces• Design and integrate the database• Prototype for design details• Design and integrate system controls---------------------------------------------------------------------------------• Construct software components• Verify and test • Convert data•Train users and document the system• Install the system

Stage 3&4: Project design/ Implementation

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Maintain system• Small patches, repairs, and updatesEnhance system• Small upgrades or enhancements to expand system capabilities• Larger enhancements may require separate development projectSupport users• Help desk and/or support team

Stage 5: Support

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• Each life cycle phase is completed in sequence• No going back once the phase is completed (like a waterfall)• The key deliverables are typically produced on paper (hundreds of pages in length)• The decisions made at each phase are frozen

SDLC approaches: Waterfall (1)

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The two key advantages of the waterfall model:• Identifying system requirements long before programming begins• It minimizes changes to the requirements as the project proceeds

The key disadvantages:• The design must be completely specified on paper before programming

begins• A paper document is often a poor communication mechanism, so

important requirements can be overlooked in the hundreds of pages of documentation

• Users rarely are prepared for their introduction to the new system, which occurs long after the initial idea for the system was introduced.

• A system may require significant rework because of changes in business environment since the time the analysis phase occurred

Waterfall model pros and cons

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Overlaps of Activities

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•The Parallel Model is doing the design and implementation in sequence, it performs a general design for the whole system• It then divides the project into series of distinct subprojects that can be designed and implemented in parallel• Once all subprojects are complete, the final integration of the separate pieces is delivered

SDLC approaches: Parallel Model (2)

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Primary advantages:

• Can reduce the schedule time required to deliver a system• There is less chance of changes in the business environment causing rework

Key disadvantages:

• Still suffers from problems caused by paper documentation• A new problem: sometimes the subprojects are not completely independent; design made in one subproject may affect another and the end of the project may require significant integrative efforts

Parallel model pros and cons

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Project cycles through development activities over and over until project is complete

Prototype created by end of each cycle Focuses on mitigating risk

SDLC approaches: Spiral model (3)

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Iteration: the process of looping through the same development activities multiple times, sometimes at increasing levels of details or accuracy

Assumes no one gets the right results the first time (version) Do some analysis, then some design, then some

implementation, then do some further analysis, etc until you get it right

the amount of iteration depends on the complexity of the project.

SDLC approaches: Iteration model (4)

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• Breaks the overall system into a series of versions that are developed sequentially• The analysis phase identifies the overall system concept. The project team, users and system sponsors categorize the requirements into a series of versions• The most important and fundamental requirements are bundled into the first version of the system.

SDLC approaches: Phased model (5)

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Advantages: Quickly getting a useful system into the hands of users. Although it does not perform all the functions the users need, it helps them sooner to identify important additional requirements

Disadvantages: The users begin to work with systems that are incomplete. It is critical to identify the most important and useful features and include them in the first version.

Pros and cons of Phased model

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• Performs analysis, design and implementation phases concurrently, • All three phases are performed repeatedly in a cycle until the system is completed.• The basics of analysis and design are performed, and work immediately begins on a system prototype

SDLC approaches: Prototyping model (6)

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The key advantages:• Very quickly provides a system for users to interact with. It reassures the users that the project team is working on the system. • The users can interact with the prototype to better understanding what it can and cannot do rather than attempting to understand a system specification on paper.The major disadvantages:• Fast-paced system releases challenge attempts to conduct careful, methodical analysis. Often the prototype undergoes such significant changes that many initial design decisions become poor ones

Prototyping model pros and cons

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End

Thank you

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