Structured Analysis - System Development Method

Represents the system in terms of data and the processes that act upon the data. The system development is organized into phases, with deliverables and milestones to measure progress. The Systems Development Life Cycle (SDLC) waterfall model typically consists of five phases. Iteration is possible among phases. Although structured analysis evolved many years ago, it remains a popular systems development method. Structured analysis is based on an overall plan, similar to a blueprint for constructing a building, so it is called a predictive approach.

Five step process:

Phase 1: - (Systems Planning) - This is probably the most important step since it is the start of the project and will include every detail. The systems planning phase usually begins with a formal request to the IT department, called systems request, which describes problems or desired changes in an information system or a business process. The purpose of this phase is to perform a preliminary investigation to evaluate an IT related business opportunity or problem. The preliminary examination is a critical step because the outcome will affect the entire development process. A key part of the preliminary investigation is a feasibility study that reviews anticipated costs and benefits and recommends a course of action based on operational, technical, economic, and time factors.

Phase 2 - (Systems Analysis) - The purpose of this phase is to build a logical model of the new system. The first step requirements modeling, where you investigate business processes and document what the new system must do to satisfy users. Requirements modeling continues the investigation that began during the systems planning phase. The deliverable for the systems analysis phase is the system requirements document. The system requirements document describes management and user requirements, costs and benefits, and outlines alternative development strategies.

Phase 3 - (Systems Design) - The purpose of this phase is to create a physical model that will satisfy all documented requirements for the system. At this stage, you design the user interface and identify necessary outputs, inputs, processes, internal and external controls, computer based and manual features to guarantee that the system will be reliable, accurate, maintainable, and secure. The deliverable for this phase is the system design specification, which presented to management and users for review and approval. Management and user involvement is critical to avoid any misunderstanding about what the new system will do, how it will do it, and what it will cost.

Phase 4 - (Systems Implementation) - The objective of this phase is to deliver a completely functioning and documented information system. During this stage, the new system is constructed. If the system was purchased as a package, systems analysts configure the software and perform any necessary modifications. At the conclusion of this phase, the system is ready to use. Final preparations include converting data to the new system's files, training users, and performing the actual transition to the new system. This phase also includes an assessment, called a systems evaluation, to determine whether the system operates properly and if costs and benefits are within expectations.

Phase 5 - (Systems Support and Security) - During this phase the IT staff maintains , enhances, and protects the system. Maintenance changes correct errors and adapt to changes in the environment, such as tax rates. Enhancements provide new features and benefits. The objective during this phase is to maximize return on the IT investment. A well-designed system must be secure, reliable, maintainable, and scalable. A scalable design can expand to meet new business requirements and volumes. Information systems development is always a work in progress. Business processes change rapidly, and most information systems need to be updated significantly or replaced after several years.

The Waterfall model is a traditional systems development life cycle (SDLC) that is a structured analysis that involves a five phase step process as mentioned above. The result of each phase is called deliverable or end product which flows into the next phase. Some analysts may see a disadvantage in the waterfall model because it does not emphasize interactivity among the phases if the phases are followed to rigidly. However, the waterfall model can be used as a two-way street with emphasis on iteration and user input, using it in this manner is not much different from agile methods as it might appear to be.

Agile Methods - Spiral Method

The Spiral method is the newer development and typically uses agile methods. An agile approach requires intense interactivity between developers and individual users, and does not begin with an overall objective. Instead, the agile process determines the end result. The agile method also adapts to changes quickly by intense feedback between developers and users. Proponents of the spiral model believe that this approach reduces risks and speeds up software development. Repeated iterations produce a series of prototypes, which evolve into a finished product. The spiral method places emphasis on iteration and user input. In contrast to the waterfall model, the waterfall model also places emphasis on iteration and user input if the phases are not followed to rigidly.

Context Diagram (DFD)

Diagram Examples:

Context

DFD

DFD 0

Symbols:

Processes

Entities

Data Flows

Data Stores

Leveling:

Decomposition, Exploding

High Level

Low level

Balancing:

Parent

Child

Processing Description Tools:

Structured English

Pseudo code

Decision Table

Decision Trees

Diagram DFD 0

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