Managing Project System

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Chapter 5
Data and Process Control

Logical Model - shows what the system must do
Physical Model - describes how the system will be constructed Data Flow Diagram - 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 Data Flow Symbol – represents one or more data items

Data Store Symbol – represents data that the system restores Creating a Set of DFD’s
1. Draw a Context Diagram
2. Draw a Diagram 0 DFD
3. Draw the Lower Level Diagrams
Data Dictionary or Data Repository – is a central storehouse of information about the system’s data * Using CASE Tools for Documentation
* Documenting the Data Elements
* Documenting the Data Flows
* Documenting the Data Stores
* Documenting the Processes
* Documenting the Entities
* Documenting the Records
* Data Dictionary Reports
Process Description Tools
* Modular Design – bases on combinations of three logical structures, sometimes called control structures, which serve as building blocks for the process * Structured English
* Decision Tables
* Decision Trees
Logical vs. Physical Models while structured analysis tools are used to develop a logical model for a new information system, such tools also can be used to develop physical models of an information system. 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. Performing that extra step allows them to understand the current system better Four-Model Approach develop a physical model of the current system, a logical model of the current system, a logical model of the new system and physical model of the new system. The only disadvantages of the four-model...
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