A Survey of Adaptive Middleware

1
A Survey of Adaptive Middleware

• SeyedMasoud Sadjadi
• www.cse.msu.edu/sadjadis
• Software Engineering and Networking Systems
  Laboratory
• Department of Computer Science and Engineering
• Michigan State University
• www.cse.msu.edu/sens

2
Agenda
Motivation
Overview
Motivation
Background
Background
Key Paradigms
Taxonomy
Examples
Key Paradigms
Big Picture
Conclusion
Taxonomy
Examples
Big Picture
Conclusion
3
Motivation
Overview

• Problem
• complexity of interprocess communication
• heterogeneity of platforms
• changing conditions
• Functional
• Environmental
• Traditional Middleware
• addresses the first two problems to some extent
• is limited in supporting adaptation
• Adaptive Middleware
• addresses all three problems
• still ongoing research

Motivation
Background
Key Paradigms
Taxonomy
Examples
Big Picture
Conclusion
4
Background
Overview

• Traditional Middleware
• connectivity software
• below application and above operation system
  layer
• provides high-level programming abstractions
• Middleware Classification by Emmerich 1

Motivation
Background
Taxonomy
OO MW
Key Paradigms
Taxonomy
Examples
Big Picture
Conclusion
5
CORBA
Overview

• CORBA
• Common Object Request Broker Architecture.
• A distributed object framework by OMG.
• Supports distributed object-oriented computing
  across heterogeneous hardware devices, operating
  systems, network protocols, and programming
  languages.

Motivation
Background
Taxonomy
OO MW
Key Paradigms
Taxonomy
Examples

• Components
• Object
• Servant
• Client
• IDL Compiler
• Stub
• Skeleton
• ORB Core
• GIOP/IIOP

Big Picture
Conclusion
CORBA architecture 2.
6
Java RMI DCOM
Overview

• Java RMI
• Java Remote Method Invocation.
• A Java distributed object framework by JavaSoft.
• Supports distributed computing across
  heterogeneous hardware devices and operating
  systems using the Java Virtual Machine (JVM).
• Serialization.
• DCOM
• Distributed Component Object Model.
• A Windows distributed object framework by
  Microsoft.
• An extension to the COM that supports
  heterogeneous programming languages and network
  protocols.
• Provides a binary standard like C vtable.
• Object proxies and object stubs in DCOM are
  referred as IDL stubs and IDL skeleton in
  CORBA, respectively!

Motivation
Background
Taxonomy
OO MW
Key Paradigms
Taxonomy
Examples
Big Picture
Conclusion
7
Agenda
Motivation
Overview
Motivation
Background
Background
Key Paradigms
Taxonomy
Examples
Key Paradigms
Big Picture
Conclusion
Taxonomy
Examples
Big Picture
Conclusion
8
Computational Reflection
Overview

• The ability of a program to reason about, and
  possibly alter, its own behavior 3.
• Enables a system to open up its implementation
  details for such analysis without revealing the
  unnecessary parts or compromising portability
  4.
• Terminology

Motivation
Background
Key Paradigms
Reflection
CBD
AOP
Patterns

• Base-level
• Meta-level
• MOP
• Casually connected
• Per-ORB, per-class, per-object, and per-interface
  reflection

Taxonomy
Examples
Big Picture
Conclusion
Relationship between meta-level and base-level
objects.
9
Component-Based Design
Overview

• Software components
• Software units that can be independently
  produced, deployed, and composed by third parties
  5.
• Self-contained
• Commodity-of-the-shelf (COTS)
• Component-based design (CBD)
• large scale reuse of software
• Composition
• late binding
• Component-Based Middleware
• DCOM
• EJB
• CCM

Motivation
Background
Key Paradigms
Reflection
CBD
AOP
Patterns
Taxonomy
Examples
Big Picture
Conclusion
Independent Components
10
Aspect-Oriented Programming
Overview

• Complex programs are composed of different
  intervened cross-cutting concerns 6.
• Cross-cutting concerns
• Properties or areas of interest such as QoS,
  energy consumption, fault tolerance, and
  security.
• Terminology

Motivation
Background
Key Paradigms
Reflection
CBD
AOP
Basic Functionality
Cross-Cutting Aspects
Patterns

• Aspect
• Basic Functionality
• Aspect Language
• Aspect Weaver
• Static
• Dynamic
• Woven Code

Taxonomy
Examples
Big Picture
Conclusion
Aspect Weaver
Woven Code
AOP in action.
11
Software Design Patterns
Overview

• Enables reuse of best software design practices
  7.
• Benefits
• common vocabulary for communicating insight and
  experience about recurring problems
• Patterns commonly used in adaptive middleware

Motivation
Background
Key Paradigms
Reflection
CBD
AOP

• Façade
• Wrapper
• Interceptor
• Strategy
• Service Configurator
• Virtual Component

Patterns
Taxonomy
Examples
Big Picture
Conclusion
Class diagram.
12
Agenda
Motivation
Overview
Motivation
Background
Background
Key Paradigms
Taxonomy
Examples
Key Paradigms
Big Picture
Conclusion
Taxonomy
Examples
Big Picture
Conclusion
13
Middleware Layers
Overview

• Schmidt 8 decomposed middleware into four
  layers

Motivation
Background

• Domain-Services
• Tailored to a specific class of distributed
  applications
• Common-Services
• Functionality such as fault tolerance, security,
  load balancing and transactions
• Distribution
• Programming-language abstraction
• Host-Infrastructure
• Platform-abstraction

Key Paradigms
Taxonomy
MW Layers
Adaptation Type
App. Domain
Examples
Middleware Layers
Big Picture
Conclusion
Note an adaptive middleware project may fall in
more than one layer.
Middleware layers 8
14
Adaptation Type
Overview
Motivation
Background
Key Paradigms
Taxonomy
MW Layers

• Static Middleware
• Customizable Middleware
• Enables developers to compile (and link)
  customized versions of applications.
• Configurable Middleware
• Enables administrators to configure the
  middleware after compile time.
• Dynamic Middleware
• Tunable Middleware
• Enables administrators to fine-tune applications
  during run time.
• Mutable Middleware
• Enables administrators to dynamically adapt
  applications at run time.

Adaptation Type
App. Domain
Examples
Big Picture
Conclusion

• Note an adaptive middleware project may provide
  more that one adaptation.

15
Application Domain
Overview
Motivation
Background
Key Paradigms

• QoS-Oriented Middleware
• supports real-time and multimedia applications
• Example
• avionics systems, video conferencing and Internet
  telephony
• Dependable Middleware
• supports critical distributed applications that
  are required to be correctly operational
• Example
• military command and control and medical
  applications
• Embedded Middleware
• supports small footprints
• Examples
• smart phones, hand-held devices, and industrial
  controllers

Taxonomy
MW Layers
Adaptation Type
App. domain
Examples
Big Picture
Conclusion

• Note there is a lot of overlap among these
  groups.

16
Agenda
Motivation
Overview
Motivation
Background
Background
Key Paradigms
Taxonomy
Examples
Key Paradigms
Big Picture
Conclusion
Taxonomy
Examples
Big Picture
Conclusion
17
QoS-Oriented Middleware
Overview
Motivation
Background
Key Paradigms
Taxonomy

• Real-Time Middleware
• Required to meet the deadlines defined by
  real-time applications
• Hard and soft real-time middleware
• Stream-Oriented Middleware
• Provides a continuous data streaming abstraction
• Reflection-Oriented Middleware
• Computational reflection is the primary focus
• Aspect-Oriented Middleware
• AOP is the primary focus

Examples
QoS-Oriented
Dependable
Embedded
Big Picture
Conclusion
18
Real-Time Middleware
Overview

• TAO
• Schmidt et al.
• CORBA compliant ORB
• Classification
• Distribution layer
• Configurable and Tunable MW
• Real-time MW

Motivation
Background
Key Paradigms
Taxonomy
Examples
QoS-Oriented
Dependable
Embedded
TAO Architecture 9.
Big Picture

• DynamicTAO
• UIUC
• A reflective TAO
• Classification
• Distribution layer
• Tunable MW
• Real-time MW

Conclusion
Reified DynamicTAO 10.
19
Stream-Oriented Middleware

• Open-ORB
• Lancaster University
• ORB-wide reflection

• Classification
• Distribution layer
• Mutable MW

Overview
Motivation
Background
Key Paradigms
Taxonomy
Examples
QoS-Oriented
Dependable
Open-ORB explicit binding 11.
Embedded
Big Picture

• Squirrel over Infopipes
• University of Kaiserslautern

• Classification
• Distribution layer
• Customizable and Tunable MW

Conclusion
Squirrel over Infopipes 12.
20
Aspect-Oriented Middleware
Overview

• QuO
• BBN Technologies
• Classification
• Common-services layer
• Customizable MW
• Aspect-oriented MW
• Static AOP

Motivation
Background
Key Paradigms
Taxonomy
Examples
QoS-Oriented
Dependable
Embedded
QuO 13.
Big Picture

• AspectIX
• University of Erlangen-Nürnberg
• Classification
• Distribution layer
• Tunable MW
• Aspect-oriented MW
• Dynamic AOP

Conclusion
Dynamic weaving of aspects in AspectIX 14.
21
Dependable Middleware
Dependable Middleware
Overview
Motivation
Background
Fault-Tolerant Middleware
Reliable-Communication Middleware
Load-Balancer Middleware
Key Paradigms
Taxonomy

• Reliable Communication Middleware
• provides reliable communication services
• residing at the host-infrastructure layer
• Fault-Tolerant Middleware
• continue operating in the presence of faults
• Load-Balancer Middleware
• continue operation even in the presence of high
  load

Examples
QoS-Oriented
Dependable
Embedded
Big Picture
Conclusion
22
Reliable Middleware

• Rocks
• University of Wisconsin
• Classification
• Host-infra. layer
• Configurable MW
• Reliable-commu. MW

• Racks
• University of Wisconsin
• Classification
• Common-services layer
• Configurable MW
• Reliable-commu. MW

Overview
Motivation
Background
Key Paradigms
Taxonomy
Examples
QoS-Oriented
Dependable
Embedded
Big Picture
Conclusion
Racks architecture 15.
Rocks architecture 15.
23
Fault-Tolerance Middleware
Overview

• IRL
• Baldoni et al.
• Classification
• Common-services layer
• Configurable MW
• Fault-Tolerant MW

Motivation
Background
Key Paradigms
Taxonomy
Examples
IRL architecture 16.
QoS-Oriented
Dependable
Embedded

• Eternal
• UCSB and Eternal Systems
• Classification
• Host-infra. layer
• Configurable MW
• Fault-Tolerant MW

Big Picture
Conclusion
Eternal architecture 17.
24
Embedded Middleware
Overview
Motivation
Background
Key Paradigms
Taxonomy

• Minimum Middleware
• Enables minimum footprint applications
• For a specific application-domain
• Fixed minimum core
• For one specific application
• No fixed core
• Swappable Middleware
• Enables optional portions of middleware to swap
  in and out dynamically
• Fixed minimum core

Examples
QoS-Oriented
Dependable
Embedded
Big Picture
Conclusion
25
Swappable Middleware
Overview

• EmbeddedJava
• Sun Microsystems
• Classification
• Host-infra. layer
• Customizable MW
• Minimum MW

Motivation
Background
Key Paradigms
Taxonomy
Examples
QoS-Oriented
Dependable
EmbeddedJava architecture 18.
Embedded
Big Picture

• ZEN
• Schmidt et al.
• Classification
• Distribution layer
• Configurable and Tunable MW
• Swappable MW

Conclusion
ZEN architecture 19.
26
Agenda
Motivation
Overview
Motivation
Background
Background
Key Paradigms
Taxonomy
Examples
Key Paradigms
Big Picture
Conclusion
Taxonomy
Examples
Big Picture
Conclusion
27
Application Domain MW Layers
Overview

• Embedded Middleware
• All-in-one vs. Layered
• Common-Services
• Domain-Services
• Many standards may be proprietary?
• Need more attention

Motivation
Background
Key Paradigms
Taxonomy
Examples
Big Picture
Conclusion
28
Adaptation Type MW Layers
Overview

• Hybrid Adaptation
• Common-Services Layer
• Customizable, Tunable, Mutable
• Mutable Middleware
• Very powerful
• Safe adaptation

Motivation
Background
Key Paradigms
Taxonomy
Examples
Big Picture
Conclusion
29
Key Paradigms and Standards
Overview

• Computational Reflection
• Component-Based Design
• Aspect-Oriented Programming
• Software-Design Patterns
• Reliable- Communication Middleware
• CORBA
• Java RMI
• DCOM

Motivation
Background
Key Paradigms
Taxonomy
Examples
Big Picture
Conclusion
30
Conclusion and Future Work
Overview

• Conclusion
• A classification for traditional middleware
• Supporting paradigms for adaptation
• A taxonomy of adaptive middleware
• Classifying adaptive middleware projects
• Future Work
• Domain-services middleware
• Common-services middleware
• Embedded middleware
• Feature interaction
• Mutable middleware
• Safe adaptation
• Higher-level paradigms

Motivation
Background
Key Paradigms
Taxonomy
Examples
Big Picture
Conclusion
31
References

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• 2 http//www.cs.wustl.edu/schmidt/corba-overvie
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Overview
Motivation
Background
Key Paradigms
Taxonomy
Examples
Big Picture
Conclusion
32
Overview
Motivation
Background
Key Paradigms

• Questions?

Taxonomy
Examples
Big Picture
Conclusion
Thank you!