System Design: Addressing Design Goals

References:

1. Bernd Bruegge and Allen H. Dutoit, "Object-Oriented Software Engineering", Third Edition, Chapter 7

7.1 - Introduction: A Redundancy Example

7.2 - An Overview of System Design Activities

7.3 - Concepts: UML Deployment Diagrams

7.4 - System Design Activities: Addressing Design Goals

7.4.1 - Mapping Subsystems to Processors and Components

7.4.2 - Identifying and Storing Persistent Data

Identifying persistent objects

Selecting a storage management strategy

• Flat files
• Relational database
• Object-oriented database

7.4.3 - Providing Access Control

The access matrix can be implements as:

• A global access table - Easy to use, but may be very sparse.
• An access control list - A linked list of the actors that have access to particular entities
• A capability list - A linked list of which entities a particular actor has access to.

Rules Lists

Dynamic access control

Authentication

Encryption

7.4.4 - Designing the Global Control Flow

Procedure-driven control

Event-driven control

Threads

7.4.5 - Identifying Services

7.4.6 - Identifying Boundary Conditions

Configuration

Start-up and shutdown

Exception handling

7.4.7 - Reviewing System Design

Is the model:

• Correct
• Complete
• Consistent
• Realistic
• Readable

7.5 - Managing System Design

7.5.1 - Documenting System Design

See also the Software Engineering Report Template provided for this class, in particular sections IV.

• Word format
• PDF format

7.5.2 - Assigning Responsibilities

Main roles of system design:

• Architect
• Architecture Liaisons
• Document Editor
• Configuration Manager
• Reviewer

7.5.3 - Communicating about System Design

New sources of complexity:

• Size
• Change
• Level of abstraction
• Reluctance to confront problems
• Conflicting goals and criteria

Techniques:

• Identify and prioritize the design goals for he system and make them explicit.
• Make the current version of the document available to all concerned
• Maintain an up-to-date glossary
• Confront design problems
• Iterate.

7.5.4 - Iterating over the System Design

7.6 - ARENA Case Study

7.6.1 - Identifying Design Goals

• Low operating cost.
• High availability
• Scalability in terms of number of players and concurrent tournaments.
• Ease of adding new games.
• Documentation for open source development.

7.6.2 - Identifying Subsystems

7.6.3 - Mapping Subsystems to Processors and Components

7.6.4 - Identifying and Storing Persistent Data

Identifying persistent objects

Selecting a storage strategy

7.6.5 - Providing Access Control

7.6.6 - Designing the Global Control Flow

7.6.7 - Identifying Services

7.6.8 - Identifying Boundary Conditions

Configuration use cases

Start-up and shutdown use cases

Exception use cases

7.6.9 Lessons Learned