System Models

Tom Kelliher, CS 319

Nov. 13, 2000

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Assignment

Read Chapter 13 --- Architectural Design.

From Last Time

Requirements analysis --- ``Human factors.''

Outline

1. System models: dataflow models, semantic data models, object models.

Coming Up

Architectural design.

System Models

• Models are abstractions, hopefully maintaining the salient features of a system.

• Models vs. representations. (Abstracts vs. translations.)

Dataflow Models

1. Show how data flows through a sequence of processing steps.

2. The model most accessible to non-technical staff?

3. Elements of a dataflow diagram:

   

4. Develop a dataflow diagram of an ATM transaction.

Semantic Data Models

1. Show the logical relationship of data within a system.

2. Entity: basically, a record.

3. Relation: The relationship between different (types of) entities.

4. Elements of an ER diagram:

   

5. What data is necessary in processing an ATM transaction? Develop an ER diagram for that data.

Object Models

1. Object class: an abstraction over a set of objects which identifies common attributes and operations or services.

2. Often a foreign concept to end-users.

3. Elements of a class hierarchy diagram:

   

4. Develop class hierarchy and object aggregation diagrams for sub-systems within an ATM system.