01-03-2013, 11:37 AM
Data Modeling
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Outline
System analysis model elements:
• Data model: entity-relationship diagram (ERD)
• Functional model: data flow diagram (DFD)
Background
Modeling consists of building an abstraction of reality. These abstractions are simplifications because they ignore irrelevant details and they only represent the relevant details (what is relevant or irrelevant depends on the purpose of the model).
Why Model Software?
Software is getting larger, not smaller; for example, Windows XP has more than 40 million lines of code. A single programmer cannot manage this amount of code in its entirety. Code is often not directly understandable by developers who did not participate in the development; thus, we need simpler representations for complex systems (modeling is a mean for dealing with complexity).
A wide variety of models have been in use within various engineering disciplines for a long time. In software engineering a number of modeling methods are also available.
Analysis Model Objectives
• To describe what the customer requires.
• To establish a basis for the creation of a software design.
• To define a set of requirements that can be validated once the software is built.
The Elements of the Analysis Model
The generic analysis model consists of:
• An entity-relationship diagram (data model).
• A data flow diagram (functional model).
• A state transition diagram (behavioral model).
NOTE: state transition diagram will be covered in lab 11.