29-04-2014, 12:42 PM
Modern Systems Analysis and Design
Modern Systems.ppt (Size: 845 KB / Downloads: 106)
Learning Objectives
Understand the logical modeling of processes by studying examples of data flow diagrams (DFDs).
Draw data flow diagrams following specific rules and guidelines that lead to accurate and well-structured process models.
Decompose data flow diagrams into lower-level diagrams.
Balance higher-level and lower-level data flow diagrams.
Use data flow diagrams as a tool to support the analysis of information systems.
Discuss process modeling for electronic commerce applications.
Use decision tables to represent the logic of choice in conditional statements.
Deliverables and Outcomes
Context data flow diagram (DFD)
Scope of system
DFDs of current physical system
Adequate detail only
DFDs of current logical system
Enables analysts to understand current system
Developing DFDs
Context diagram is an overview of an organizational system that shows:
the system boundaries.
external entities that interact with the system.
major information flows between the entities and the system.
Note: only one process symbol, and no data stores shown
Data Flow Diagramming Rules
There are two DFD guidelines that apply:
The inputs to a process are different from the outputs of that process.
Processes purpose is to transform inputs into outputs.
Objects on a DFD have unique names.
Every process has a unique name.
Decomposition of DFDs
Functional decomposition is an iterative process of breaking a system description down into finer and finer detail.
Creates a set of charts in which one process on a given chart is explained in greater detail on another chart.
Continues until no subprocess can logically be broken down any further.
Using DFDs as Analysis Tools
Gap Analysis is the process of discovering discrepancies between two or more sets of data flow diagrams or discrepancies within a single DFD.
Inefficiencies in a system can often be identified through DFDs.