18 October 2001

1
Pattern Usage in an Avionics Product Line

• Wendy Roll - wendy.c.roll_at_boeing.com
• David Sharp david.sharp_at_boeing.com
• The Boeing Company

presenter
2
Outline

• Domain Characteristics
• Technical and Developmental Forces
• Architecture Development Process
• Examples of Pattern Usage Evolution
• Pattern Relationships

3
Fighter Avionics Operational Domain-
Characteristics
Constrained Tactical Links
Many Computers
Periodic Aperiodic
Multiple Buses
Mission Computer
Vehicle Mgmt
Radar
COTS
Hard Soft Real-Time
O(106) Lines of Code
4
Fighter Avionics Operational Domain- Example
Functionality
Update Steering Cues
Fuse Targets From Sensors
Fuse Targets From Data Links
Mission Computer
Perform Built-In-Test
Activate Backup Mode
Update Navigation State
Release Weapons
Select Weapons
Update Displays
Predict Selected Weapon Trajectories
Modify Display Suite Via Pilot Pushbutton
Aperiodic
Periodic
5
Technical and Developmental Forces

• Technical Forces
• Product Line Variability
• Operating Systems, HW Architectures
• Sensors, Displays, Other External Devices
• Functional Requirements
• Performance
• Developmental Forces
• Technical/Cultural Revolution in Boeing
• OO Technology, C, CORBA
• Product Line Development Complexity
• Increasingly Large Team of Developers

6
Architecture Development
1 Develop Architecture Goals
4 Use Goals to Drive Architecture Development
Decisions
Developed Architecture
Patterns
t
3 Use Concrete Development to Identify
Architectural Issues
2, 5 Develop and Measure Domain Components
Domain-Driven, Goal-Guided Architecture
Development
7
Architecture Goals
in the Logical and Physical Architectures
Contain Change

• Isolate avionics system specifics
• Support both single and multi-CPU systems

Maximize Reuse

• Maximize pluggability of software components

Real-Time Performance
Software Architecture Requires Meeting Product
Line Goals within Real-Time Performance
8
Architectural Patterns

• Layered Architecture
• Separate high and low level concerns
• Control dependencies
• Provide overall system structure
• Model/View/Controller Architecture
• Separate core domain representation from user
  interface

D e p e n d e n c i e s
9
Multi-Dimensional Layering Pattern
D e p e n d e n c i e s
D e p e n d e n c i e s
10
Component Patterns

• Strategic Patterns That Define
• Different component types
• Component
• Configurable Component
• Distributable Component
• Real Time Component
• Tradeoffs and consequences of design choices
• Implementation issues

Component Patterns Guide Application Development
Organization
11
Component Structure

• Based on Facade Design Pattern

ComponentConsumer
ComponentSupplier1
ComponentSupplier2
12
Component PatternConsequences

• Encapsulates Change
• Defines Distribution Boundaries
• Localizes Concurrency Control
• Identifies Pluggable Entities
• Enhances Reusability
• Reduces Complexity
• Defines Object Ownership

13
Abstract Factory-Smart Facade

• Abstract Factory Pattern Defines Configuration
  Technique

HorizontalSubstate
VerticalSubstate
RotationalSubstate
1..
1..
1..
1..
1..
1..
HorizontalSensor
VerticalSensor
RotationalSensor
14
Component Evolution

• Currently exploring CORBA Component Model Concepts

ltltInterfacegtgt
ComponentEquivalentInterface
Component
GetFacet()
Extension Interface Pattern used for smaller
role-based facets
ltltInterfacegtgt
Facet1
GetData()
EventSinkAdapter
ltltInterfacegtgt
Facet2
EventSourceAdapter
PointAt()
ltltInterfacegtgt
ltltInterfacegtgt
EventSource
EventSink
Push()
Push()
15
Control Flow

• Desired Variabilities
• Simplify and isolate standard interfaces
• Number and types of components
• System execution modes
• Notification types
• periodic, multiple entry points and correlated
• Patterns
• Observer, mediator, and external polymorphism

16
Control Flow
Mediator Pattern removes supplier knowledge
consumer
Events remove modal dependencies
5 consumer message
consumer
supplier
Ext. Polymorph Pattern isolates standard
interfaces
Adapter
1 push
4 push
Dispatch
consumer
supplier
Proxy
Proxy
Correlation
2 push
Complex event dependencies support variable
notification
Subscription
3 push
event
Event Service
Channel
Anonymous Supplier and Consumer Communication for
Control Flow Preserves Encapsulation of
Dependencies
17
Communication - Data

• Desired Variabilities
• Flexible component-to-processor allocation
• Isolation from network protocols
• Optimization of network performance
• Patterns
• Broker, proxy, caching proxy

18
Communication - Data ReadsRemote Communication
Reads From Local and Remote Clients Appear
Identical
Processor 1
Processor 2
remote
local
Client
Client
5 GetPosition
6 GetPosition
Caching Proxy Pattern hides supplier location,
hides effects of network bandwidth, and isolates
broker implementation
supplier
supplier
Master
DistProxy
4 SetData
1 GetData
replication
replication
Proc2
Proc1
CORBA ORB
2 SetData
3 SetData
Broker Pattern isolates network protocols
orbProc1
orbProc2
19
Communication - Data WritesRemote Communication
Writes To Local and Remote Suppliers Appear
Identical
Processor 1
Processor 2
remote
local
Client
Client
4 SetMode
1 SetMode
supplier
supplier
Proxy hides supplier location
Master
DistProxy
2 SetMode
3 SetMode
CORBA ORB
Broker pattern isolates network protocols
orbProc1
orbProc2
20
Pattern Map for Avionics PL
Arch Structure
Concurrency
No Locking
Internal Locking
Layers
Null Lock
Concurrency
MVC
Multi-Dim Layers
External Locking
Null Object
Doc-View
Abstract Factory
Synch Cache Proxy
Component
Dual Inheritance Hierarchy
Adapter
Distributed Proxy
Façade
Object Adapter
Callback
Passive Objects
Proxy
Control Flow
Distribution
Mediator
Observer
Ext Poly
Cache Proxy
Strategy