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3.2 data and process modelling - Coggle Diagram
3.2 data and process modelling
Concepts
Other relelated tools including data dictionary and process descriptions
data flow diagram (DFD) uses various symbols to show how the system transforms input data into useful information.
shows how data moves through an information system but does not show program logic or processing steps( flow of data between process).
DFD Symbols
Process symbol
Data flow symbol
Data store symbol
Entity Symbol
Creating a set of DFD
Create a graphical model based on your fact-finding results
Then you will learn how to apply these guidelines and create a set of DFDs using a three-step process
Step 1 : Draw a context diagram
Step 2: Draw a Diagram 0 DFD
Step 3: Draw the Lower-Level Diagrams
Balancing example
Leveling example
Data Dictionary
A data dictionary, or data repository, is a central storehouse of information about the system’s data
to collect, document, and organize specific facts about the system
data element, also called a data item or field, is the smallest piece of data that has meaning
Data elements are combined into records, also called data structures
A record is a meaningful combination of related data elements that is included in a data flow or retained in a data store
Using CASE Tools for Documentation
more complex the system, the more difficult it is to maintain full and accurate documentation
Modern CASE tools simplify the task
Documenting the Data Elements
to provide clear, comprehensive information about the data and processes that make up the system
Documenting the Data Flows
Documenting the Data Stores
Documenting the Data Stores
Documenting the Entities
Documenting the Records
Process Description
documents the details of a functional primitive, which represents a specific set of processing steps and business logic
Modular design
Structured English
Decision Table
Modular design
Symbol
rectangle (process)
diamond (condition or decision)
The logic follows the lines in the direction indicated by the arrows.
Sequence
completion of steps in sequential order, one after another.
Selection
the system tests the input, and if the hours are greater than 40, it performs the CALCULATE OVERTIME PAY process
Iteration
process that continues to print paychecks until it reaches the end of the payroll file.
Structure English
Use a limited vocabulary, including standard terms used in the data dictionary and specific words that describe the processing rules
Might look familiar to programming students because it resembles pseudocode
Decision Tables
Shows a logical structure, with all possible combinations of conditions and resulting actions
Types of tables;
Tables with one condition
Tables with two condition
Tables with three condition
Table with multiple outcomes
Logical & Physical Model
A physical model shows how the system’s requirements are implemented
Sequence of Models
Many systems analysts create a physical model of the current system and then develop a logical model of the current system before tackling a logical model of the new system
Four-Model Approach
The only disadvantage of the four-model approach is the added time and cost