18-08-2012, 03:04 PM
Data Flow Diagrams
Data Flow.ppt (Size: 159.5 KB / Downloads: 176)
S.S.A.D.M.
S.S.A.D.M. - Structured Systems Analysis and Design Method
Uses different techniques to model a system
Data Flow Diagrams
Entity Relational Model (Logical Data Stores)
Normalisation
What is a Data Flow Diagram?
Known as DFDs
A way to model a real world situation
They are the interface between the real world activities and an understanding of how this can be converted into a computer system.
Why do we use DFDs?
It is a way of taking the physical view and converting it into a logical view.
The physical view - all documents involved
The logical view - the data they contain
Their main purpose is to communicate with the user, the analyst’s understanding of the scope of the required system
Levelling
DFDs are expanded or decomposed into levels.
Separating each process into sub processes
Uncovers more and more detail
Decomposition and Abstraction
Decomposition - Divide and subdivide into manageable size problems
Abstraction - Concentrate on the important issues and ignore the irrelevant
Data Flow
Is shown by a line with an arrowhead, indicating the direction of the flow of data. Each data flow should be named to indicate what data is being passed. Nouns or adjectives only no verbs are permitted.
Data Flow.ppt (Size: 159.5 KB / Downloads: 176)
S.S.A.D.M.
S.S.A.D.M. - Structured Systems Analysis and Design Method
Uses different techniques to model a system
Data Flow Diagrams
Entity Relational Model (Logical Data Stores)
Normalisation
What is a Data Flow Diagram?
Known as DFDs
A way to model a real world situation
They are the interface between the real world activities and an understanding of how this can be converted into a computer system.
Why do we use DFDs?
It is a way of taking the physical view and converting it into a logical view.
The physical view - all documents involved
The logical view - the data they contain
Their main purpose is to communicate with the user, the analyst’s understanding of the scope of the required system
Levelling
DFDs are expanded or decomposed into levels.
Separating each process into sub processes
Uncovers more and more detail
Decomposition and Abstraction
Decomposition - Divide and subdivide into manageable size problems
Abstraction - Concentrate on the important issues and ignore the irrelevant
Data Flow
Is shown by a line with an arrowhead, indicating the direction of the flow of data. Each data flow should be named to indicate what data is being passed. Nouns or adjectives only no verbs are permitted.