6 modeling system requirements
TRANSCRIPT
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Modeling System RequirementsSystems Analysis and Design
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Models and Modeling
• A model is a representation of some aspect of the system being built.
• The purpose of models:– models help the analyst clarify and simplify the
design– Models assist in the communication between
system users and developers and foster understanding
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Models and Modeling
• Types of models– Mathematical Models• Formulas that describe technical aspects of the system
– Descriptive Models• Narrative memos, reports or lists that describe some
aspect of a system
– Graphical Models• Diagrams and schematic representations of some
aspect of the system
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Models Used in Systems Analysis and Design
• Models created during analysis phase– Entity-Relationship Diagram– Activity Diagram
• Models created during the design phase– Screen/Report Layout– System Flowchart– Database Design/Schema– Network Diagram– Structure Chart (HIPO)
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Entity Relationship Diagram
• An entity relationship diagram is a model used to define the data storage requirement. – Data entities • The things the system needs to store information about• Contains an identifier and attributes
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Entity Relationship Diagram
• A simple ERD:
Customer Order
A customer can place zero or more orders
Order must be placed by exactly one customer
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Entity Relationship Diagram
• Cardinality Symbols of Relationships
Exactly One (Mandatory)
Zero or One (Optional)
Zero or more (Optional)
One or more (Mandatory)
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Entity Relationship Diagram
• An expanded ERD with attributes shown:
CustomerCust NumberNameAddressPhone
OrderOrder IDOrder Date Amount
Order ItemItem ID
QuantityPrice
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Screen/Report Layout
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Database Design/Schema
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Network Diagram
• A computer network diagram is a schematic depicting the nodes and connections amongst nodes in a computer network
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Structure Chart (HIPO)
• A structure chart is a design tool that pictorially shows the relation between processing modules in computer software.