1 ISA&D7/8/2013. 2 ISA&D7/8/2013 Systems Development Life Cycle Phases and Activities in the SDLC...
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Transcript of 1 ISA&D7/8/2013. 2 ISA&D7/8/2013 Systems Development Life Cycle Phases and Activities in the SDLC...
1ISA&D7 /8/2013
Approaches to system development
2ISA&D7 /8/2013
• Systems Development Life Cycle• Phases and Activities in the SDLC • Variations of the SDLC models
Lecturer details
3ISA&D7 /8/2013
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)
4ISA&D7 /8/2013
• 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
5ISA&D7 /8/2013
• 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
6ISA&D7 /8/2013
• 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
7ISA&D7 /8/2013
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
8ISA&D7 /8/2013
• 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)
9ISA&D7 /8/2013
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
10ISA&D7 /8/2013
Overlaps of Activities
11ISA&D7 /8/2013
•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)
12ISA&D7 /8/2013
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
13ISA&D7 /8/2013
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)
14ISA&D7 /8/2013
15ISA&D7 /8/2013
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)
16ISA&D7 /8/2013
17ISA&D7 /8/2013
• 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)
18ISA&D7 /8/2013
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
19ISA&D7 /8/2013
• 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)
20ISA&D7 /8/2013
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
21ISA&D7 /8/2013
End
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