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Chapter 5: Data and Process Analysis

Overview

• Focuses on data and process modeling concepts and tools.

• Important tools include data flow diagrams (DFDs), data dictionaries, and process descriptions.

Chapter Objectives

• Data and Process Modeling Concepts:

  • Understand key concepts and tools for modeling data and processes.

• Data Flow Diagrams (DFDs):

  • Learn to describe the symbols used in DFDs and how to draw them.

• Data Dictionary:

  • Understand how to use a data dictionary and what information it contains.

• Process Description Tools:

  • Learn about structured English, decision tables, and decision trees.

• Model Relationships:

  • Describe relationships between logical and physical models.

Introduction

• The logical model defines 'what' the system must do, while the physical model explains 'how' it will be implemented.

Modeling Tools

• Graphical Techniques for Information Systems:

  • Systems analysts employ various graphical techniques including DFDs to represent data flow and how input data is converted into useful information.

Data Flow Diagrams (DFDs)

• DFDs illustrate how data moves through the system without detailing program logic.

DFD Symbols

• Four basic DFD symbols represent:

  • Processes: Functions that receive input data and produce output.

  • Data Flows: Paths for data movement, represented by arrows.

  • Data Stores: Where data is stored in the system.

  • Entities: Sources or destinations of data.

Examples of DFD Symbols

• 'Gane and Sarson' and 'Yourdon' are common symbol sets in DFDs.

• Process symbols are rectangles with rounded corners, names within indicating their function.

• Data flow symbols are lines with arrows, representing either single data items or sets of data.

Creating DFDs

• Step-by-step Approach:

  1. Draw a Context Diagram:

     • A high-level overview that fits on one page.

  2. Draw a Diagram 0 DFD:

     • Explodes the high-level process into more detailed parts.

  3. Draw Lower-level Diagrams:

     • Provides further detail using techniques like leveling and balancing.

Data Dictionary

• A central repository for information about system data, defining data elements and their combinations.

• Data Elements: The smallest meaningful units of data, documented in ways such as:

  • Name

  • Type

  • Length

  • Default values and acceptable values.

Process Description Tools

• Tools like structured English, decision tables, and decision trees are essential for documenting the details of processes.

Logical vs Physical Models

• Logical models emphasize the system’s requirements, while physical models detail the implementation.

• Using a four-model approach can aid understanding current and new systems better but may increase time and cost.

Chapter Summary

• Key tools in data and process analysis include DFDs and data dictionaries.

• DFDs visualize data movement, while the data dictionary serves as a comprehensive documentation tool for structured analysis.

• Analytical tools support both logical modeling in analysis and physical modeling in design.