Æliens

Distributed Object Patterns

• Software Engineering: risk challenge
• CORBA - guidance (OO, C/S, IDL)
• Object-Oriented Architectures

Corba Design Patterns

scale



• Objects/Classes
• MicroArchitectures
• Framework

  (class hierarchies)

  
  
• Applications

  (wrappers)

  
  
• System

  (horizontal, vertical, metadata)

  
  
• Enterprise

  reference models, infrastructure, policies)

  
  
• Intra/Internet

  (standards)

  
  

Object-Oriented Architectures

• Application Design Patterns
• System Design Patterns
• Enterprise Design Patterns
• Global Design Patterns

Template Design Pattern

• Pattern Name
• Most applicable scale
• Solution type
• Intent
• Diagram
• Referemces
• Applicability
• Benefits and consequences
• Variations
• Rescaling to other levels
• Related solutions
• Example
• Background
• Resources

Is there competition for patterns?

• standards -- too many, no guidelines, poorly supported

Criteria

• interoperability
• portablity

CORBA

• is a commercial standard from OMG, whose mission it is to define interfaces for interoperable software using object-oriented technology

Object Management Architecture

• high level infra-structure for distributed computing
• reusable modular software
• distributed heterogeneous systems

Key reasons for CORBA in the future

• IDL -- universal notation for software interfaces
• ORB -- infra-structure simplifies distributed computing

Architectures and Boundaries

• surprisingly little detail is included in OOAD models
• interfaces are treated as coding details, to be fleshed out at the programming level

• architecture -- abstraction, management of change, complexity
• interfaces -- language independent
• implementation -- software modules

software problems are due to poor definitions and transfer of software boundaries

architecture = set of rules, guidelines, interface conventions

The architect defines a robust set of abstractions that manage complexity, change and other forces

• issues of software partitioning

  logical separation

  
  
• flow of control
• flow of information
• timing and throughput
• interface layering
• hardware/software allocation
• error handling

  frequently overlooked

  
  

In a distributed system, the lack of a single address space and the need for independent reusable services are addressed by having a service-based architecture

... mandating a single type system for all applications is unrealistic ...

risk is the universal force

Design Pattern Language -- Primal Forces

• Functionality -- to meet end users requirements
• Performance -- computation/network bound
• complexity -- hotspots, redesign, abstraction
• Change -- adaptability ...
• IT Resources -- hardware / software
• Technology Transfer -- education has a price tag

Application Design Patterns

• maximizing parallelism -- distributed callback, partial processing, independent objects
• improving object implementations -- dynamic attributes, instance reference, object wrapper, lock
• modifying client stubs and other tricks -- library skeleton, fine-grained framework

System Design patterns -- horizontal, vertical, meta-data

• Principles of object-oriented architectures ---architecture mining
• fundamental structural patterns -- repository architecture, gateway
• advanced system design -- architecture enforcement, replication, agents
• Using OMG CORBA Services -- naming, trader, notification

Enterprise Design Patterns -- organisational infra structure

Global Design Patterns -- open systems/Int(e)r(a)net