RAD Review

1
RAD Review

• Describes system completely from actors point of
  view
• Basis of client developer communication
• Platform for launch of system design
  development
• Provides these specific items
• Set of nonfunctional requirements and constraints
• Use case model describing functionality of system
  from clients perspective
• Object model describing entities manipulated by
  system
• Sequence diagram for each use case showing
  sequence of interactions among participating
  objects
• Analysis Model

2
Design Overview

• Design Overview (Ch 6)
• Review of RAD
• System Design
• System Design Concepts
• System Design Goals
• (Global) System Design (Ch 7)
• Design Goals
• Software Architecture
• Boundary Use Cases
• SDD
• Subsystem Design
• Patterns (Ch 8)
• Interfaces (Ch 9)
• Mapping to Code (Ch 10)

3
System Design Concepts

• Subsystems
• Relate to Analysis Objects
• Coupling and Cohesion
• Services / Subsystem Interfaces
• Hierarchical Decomposition
• open v closed
• Partition Decomposition
• Architectural Styles pp. 237 246
• Repository classic DB
• Model/View/Controller
• Client/Server
• Peer to Peer
• 3-Tier Interface Application Logic Storage
• 4-Tier Client Interface Server Interface
  Application Logic Storage
• Pipe Filter ps auswww grep lacher sort
  more

4
System Design Activities

• 0. Starting Point RAD
• 1. Identify Design Goals from non-functional
  requirements
• performance criteria p. 249
• dependability criteria p. 249
• cost criteria p. 250
• maintenance criteria p. 250
• end user criteria p. 251
• Design Goal Tradeoffs p. 251
• 2. Identify Subsystems
• influenced by
• use cases
• lower cross-boundary associations lower
  coupling
• functionally related objects higher cohesion

5
System Design Activities (cont)

• 3. Address Design Goals
• Note BEFORE subsystem designs
• Select OTS legacy components
• Map subsystems to hardware
• Proxy Design Pattern
• Plan infrastructure for management of persistent
  data
• Identify persistent objects
• Select storage management strategy see fig 7-7,
  p. 269
• flat files
• relational DB
• OODB
• Specify access control policies can of worms
• Global access table
• Access control map (associated with each class)
  table.column
• Capability map (associated with each actor)
  table.row

6
System Design Activities (cont)

• 3. Address Design Goals (cont)
• Design global control flow
• Procedure Driven
• Event Driven
• Threaded
• Identify boundary conditions
• Configuration
• Startup / Shutdown
• Exception Handling
• Administration Use Cases generated by design
  team
• Key Roles
• Architect
• Architecture Liaisons member of subsystem team
• Document Editor
• Configuration Manager
• Reviewer

7
Iteration!
8
Closing the Gap

• Client with problem ... Machine huge
  distance
• Analysis, resulting in RAD ... Machine gap
  is smaller
• System Design, resulting in SDD ... Machine
  smaller still
• At this point SDD should specify a virtual
  machine VM
• Object design and mapping to code reduce gap even
  further, to point where compilers completely
  close the gap
• Notice that we always work from left to right
  (with feedback loops)
• Client -gt Analysis -gt RAD -gt System Design -gt SDD
  -gt Object Design
• -gt Code -gt Build -gt executable system
• Feedback loops at each stage
• Changes at any stage usually require re-work of
  all following stages, so emphasis should be on
  localized feedback loops (i.e., go back only one
  step, repeat until correct)