Systems Analysis and Design Overview
Systems Analysis and Design Overview
- Systems Analysis:
- A systematic process of collecting and interpreting facts, identifying problems, and decomposing a system into its components.
- Conducted for the purpose of studying a system or its parts to identify its objectives.
- Functions as a problem-solving technique that improves the system and ensures all components work efficiently to accomplish their purpose.
- Specifies what the system should do.
- Systems Design:
- A process of planning a new business system or replacing an existing system by defining its components or modules to satisfy specific requirements.
- Requires a thorough understanding of the old system and determining how computers can best be used to operate efficiently.
- Focuses on how to accomplish the objective of the system.
- Core Focus Areas of Systems Analysis and Design (SAD):
- Systems
- Processes
- Technology
Concept and Definition of a System
- Etymology: The word System is derived from the Greek word Systema, which means an organized relationship between any set of components to achieve some common cause or objective.
- Definition: A system is defined as "an orderly grouping of interdependent components linked together according to a plan to achieve a specific goal."
- Basic Constraints of a System:
- A system must have a specific structure and behavior designed to achieve a predefined objective.
- Interconnectivity and interdependence must exist among the system components.
- The objectives of the organization have a higher priority than the objectives of its subsystems.
Properties of a System
- Organization:
- Implies structure and order within the system.
- Refers to the arrangement of components that helps to achieve predetermined objectives.
- Interaction:
- Defined by the manner in which components operate with each other.
- Example: In an organization, the purchasing department must interact with the production department, and the payroll department must interact with the personnel department.
- Interdependence:
- Refers to how the components of a system depend on one another for proper functioning.
- Components are coordinated and linked together according to a specified plan.
- The output of one subsystem is required by another subsystem as input.
- Integration:
- Concerned with how system components are connected together.
- Means that the parts of the system work together within the total system, even if each part performs a unique individual function.
- Central Objective:
- The objective of a system must be central, which may be real or stated.
- It is not uncommon for an organization to state one objective and operate to achieve another.
- Users must know the main objective of a computer application early in the analysis stage for a successful design and conversion.
Elements of a System
- Outputs and Inputs:
- The main aim of a system is to produce an output that is useful for its user.
- Inputs consist of information or resources that enter the system for processing.
- Output is the outcome of the processing stage.
- Processor(s):
- The operational component of a system that performs the actual transformation of input into output.
- Processors may modify input either totally or partially depending on the output specification.
- As output specifications change, processing changes accordingly.
- In some cases, input is also modified to enable the processor to handle the transformation.
- Control:
- Guides and governs the system.
- Acts as the decision-making subsystem controlling the pattern of activities governing input, processing, and output.
- In a computer system, behavior is controlled by the Operating System and software.
- Output specifications determine what input and how much input is needed to keep the system in balance.
- Feedback:
- Provides control in a dynamic system.
- Positive Feedback: Routine in nature; encourages and reinforces the performance of the system.
- Negative Feedback: Informational in nature; provides the controller with information required for action.
- Environment:
- The "supersystem" within which an organization operates.
- Serves as the source of external elements that strike on the system.
- Determines how a system must function (e.g., external vendors and competitors present constraints that affect business performance).
- Boundaries and Interfaces:
- Boundaries are the limits that identify a system's components, processes, and interrelationships when interfacing with another system.
- Determines the sphere of influence and control for each system.
- Knowledge of system boundaries is crucial in determining the nature of its interface with other systems for successful design.
Types of Systems
- Physical or Abstract Systems:
- Physical Systems: Tangible entities that can be touched and felt. They can be static (e.g., desks and chairs in a computer center) or dynamic (e.g., a programmed computer in which programs, data, and applications change according to user needs).
- Abstract Systems: Non-physical or conceptual entities, such as formulas, representations, or models of a real system.
- Open or Closed Systems:
- Open System: Interacts with its environment by receiving inputs from and delivering outputs to the outside of the system (e.g., an information system that must adapt to changing environmental conditions).
- Closed System: Completely isolated from environmental influences and does not interact with its environment (completely closed systems are rare in reality).
- Adaptive and Non-Adaptive Systems:
- Adaptive Systems: Respond to changes in the environment in a manner that improves performance and survival (e.g., human beings, animals).
- Non-Adaptive Systems: Do not respond to environmental changes (e.g., machines).
- Permanent or Temporary Systems:
- Permanent System: Persists for a long duration (e.g., business policies).
- Temporary System: Designed for a specified time frame and demolished afterward (e.g., a DJ system setup for a specific program and disassembled after completion).
- Natural and Manufactured Systems:
- Natural Systems: Created by nature (e.g., solar system, seasonal system).
- Manufactured Systems: Man-made systems (e.g., rockets, dams, trains).
- Deterministic or Probabilistic Systems:
- Deterministic System: Operates in a completely predictable manner where interactions between components are known with certainty (e.g., two molecules of hydrogen and one molecule of oxygen forming water).
- Probabilistic System: Shows uncertain behavior where exact output is not known (e.g., weather forecasting, mail delivery).
- Social, Human-Machine, and Machine Systems:
- Social Systems: Composed of people (e.g., social clubs, societies).
- Human-Machine Systems: Involves both humans and machines working together to perform a task (e.g., computer programming).
- Machine Systems: Autonomous systems where human interference is neglected and all tasks are performed by the machine (e.g., an autonomous robot).
- Man-Made Information Systems:
- An interconnected set of information resources designed to manage data for an organization under Direct Management Control (DMC).
- Includes hardware, software, communication, data, and applications to produce information according to organizational needs.
- Divided into three types:
- Formal Information Systems: Based on the flow of information in the form of memos, instructions, etc., from top-level to lower levels of management.
- Informal Information Systems: Employee-based systems that solve day-to-day work-related problems.
- Computer Based Systems: Directly dependent on computers for managing business applications (e.g., automatic library systems, railway reservation systems, banking systems).
Systems Models
- Schematic Models:
- A two-dimensional chart that shows system elements and their linkages.
- Uses different arrows to depict information flow, material flow, and information feedback.
- Flow System Models:
- Shows the orderly flow of material, energy, and information that holds the system together.
- Example: Program Evaluation and Review Technique (PERT) is used to abstract a real-world system in model form.
- Static System Models:
- Represents one pair of relationships, such as activity–time or cost–quantity.
- Example: A Gantt chart provides a static picture of an activity-time relationship.
- Dynamic System Models:
- Approximates dynamic business organizations by capturing an ongoing, constantly changing system status.
- Consists of:
- Inputs that enter the system
- The processor through which transformation takes place
- The program(s) required for processing
- The output(s) that result from processing
- Strategic Information:
- Management Level: Required by upper / topmost management.
- Planning Scope: Long-range planning policies spanning the next few years (e.g., trends in revenues, financial investment, human resources, population growth).
- Information Attributes: Low volume, condensed, and unstructured.
- System Support: Decision Support System (DSS).
- Managerial Information:
- Management Level: Required by middle management.
- Planning Scope: Short and intermediate-range planning measured in terms of months (e.g., sales analysis, cash flow projections, annual financial statements).
- Information Attributes: Medium volume, moderately processed, and moderately structured.
- System Support: Management Information Systems (MIS).
- Operational Information:
- Management Level: Required by lower management.
- Planning Scope: Daily and short-term planning to enforce day-to-day operational activities (e.g., employee attendance records, overdue purchase orders, current stock available).
- Information Attributes: Large volume, detailed reports, and highly structured.
- System Support: Data Processing Systems (DPS).
