Reflective- Adaptive Middleware

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Reflective- Adaptive Middleware

• Leila Jalali
• Distributed Systems Middleware ICS 237
• Prof. Venkatasubramanian
• Fall 2008

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Outline
Motivation
Overview
Motivation
Background
Background
Key Paradigms
Taxonomy
Examples
Key Paradigms
Conclusion
Taxonomy
Examples
Conclusion
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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
• Reflective and Adaptive Middleware
• addresses all three problems
• still ongoing research

Motivation
Background
Key Paradigms
Taxonomy
Examples
Conclusion
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Background
Overview

• Traditional Middleware
• Middleware Classification by Emmerich 1

Motivation
Background
Key Paradigms
Taxonomy
Examples
Conclusion
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Computational Reflection
Overview

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

Motivation
Background
Key Paradigms
Reflection
Taxonomy
Examples

• Base-level
• Meta-level
• Reification
• MOP

Conclusion
Relationship between meta-level and base-level
objects
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Why Reflective Middleware?
Overview

• Wireless communication, mobile computing and
  real-time applications demand
• High adaptability
• dynamic customization of systems, services and
  communication protocols
• Safe flexibility
• constrain composition of services and protocols
  in order to prevent functional interference that
  could lead to an inconsistent state of the system
• required to protect the system from security
  threats and failure
• Cost-effective QoS guarantees

Motivation
Background
Key Paradigms
Reflection
Taxonomy
Examples
Conclusion
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Reflection
Overview

• Provides a plug-and-play environment for enabling
  run-time modification of policies
• An efficient technique to build composable
  middleware
• Features
• Separation of concerns
• Flexibility, Adaptability
• Composition
• Implies concurrent execution of multiple resource
  management policies

Motivation
Background
Key Paradigms
Reflection
Taxonomy
Examples
Conclusion
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Reflection Reification
Overview

• Reflection
• Behavioral reflection
• Structural reflection
• Metaobject protocol
• reflection object-oriented programming

Motivation
Background
Key Paradigms
Reflection
Taxonomy
Examples
Conclusion
Meta-level
Reification
Reflection
Base-level
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Reification
Overview

• What can you reify?
• Structural reflection the models of your program
  (MDA), the structure of structured files (e.g.
  XML DTDs), the classes of a program, the code of
  a program (AST), the object structures (rarely),
  the bytecode of a class.
• at design-time, compile-time, at load-time, or at
  runtime.
• Behavioral reflection the object behavior (e.g.
  when they change states), the interaction between
  the objects (e.g. when a client invokes a remote
  object, when an invocation arrives on an object).
• at runtime, (design-time, compile time partial
  reification).

Motivation
Background
Key Paradigms
Reflection
Taxonomy
Examples
Conclusion
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Outline
Motivation
Overview
Motivation
Background
Background
Key Paradigms
Taxonomy
Examples
Key Paradigms
Big Picture
Conclusion
Taxonomy
Examples
Conclusion
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Middleware Layers
Overview

• Schmidt 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
Conclusion
Note an adaptive middleware project may fall in
more than one layer.
Middleware layers 8
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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
Conclusion

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

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Application Domain
Overview
Motivation
Background
Key Paradigms

• QoS-Oriented Middleware
• supports real-time and multimedia applications
• Example
• 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
Conclusion

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

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Outline
Motivation
Overview
Motivation
Background
Background
Key Paradigms
Taxonomy
Examples
Key Paradigms
Conclusion
Taxonomy
Examples
Conclusion
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QoS-Oriented Middleware
Overview
Motivation
Background
Key Paradigms
Taxonomy
Examples
QoS-Oriented
TLAM
Conclusion

• Reflection-Oriented Middleware
• Computational reflection is the primary focus

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TLAM
Overview
System (Meta) Level

• Two Level Meta Architecture (TLAM)

Motivation
Background
Replication
Access Control
Key Paradigms
DGC
Taxonomy
Migration
Check- pointing
Examples
QoS-Oriented
TLAM
Remote Creation
Distributed Snapshot
Directory Services
Conclusion
Application (Base) Level

• Core services allow to isolate complex
  interactions
• -- useful for managing composition of services

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Reflective middleware framework CompOSEQ
Motivation
Background
QoS Broker
Key Paradigms
Taxonomy
Data Mgmt
Request Mgmt
Examples
QoS-Oriented
TLAM
Conclusion
De-replication
Data Placement
Message Scheduling
Request Scheduling
Application Objects
Clock Sync
Migration
Replication
Core Services
Remote Creation
Distributed Snapshot
Directory Services
Interaction with Core Services
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Conclusion and Future Work
Overview

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

Motivation
Background
Key Paradigms
Taxonomy
Examples
Conclusion
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References

• 1 Wolfgang Emmerich. Software engineering and
  middleware a roadmap. In Proceedings of the
  Conference on The future of Software engineering,
  pages 117-129, 2000.
• 2 http//www.cs.wustl.edu/schmidt/corba-overvie
  w.html.
• 3 Pattie Maes. Concepts and experiments in
  computational reflection. In Proceedings of the
  ACM Conference on Object-Oriented Languages
  (OOPSLA), December 1987.
• 4 G. Kiczales, J. d. Rivieres, and D. G.
  Bobrow. The Art of Metaobject Protocols. MIT
  Press, 1991.
• 5 Clemens Szyperski. Component Software Beyond
  Object-Oriented Programming. Addison-Wesley,
  1999.
• 6 Erich Gamma, Richard Helm, Ralph Johnson, and
  John Vlissides. Design Patterns Elements od
  Reusable Object-Oriented Software. Addison-Wesley
  Professional Computing Series. Addison-Wesley
  Publishing Company, New York, NY, 1995.
• 7 G. Kiczales, J. Lamping, A. Mendhekar, C.
  Maeda, C. Videira Lopes, J. M. Loingtier, and J.
  Irwin. Aspect-oriented programming. In
  Proceedings of the European Conference on
  Object-Oriented Programming (ECOOP).
  Springer-Verlag LNCS 1241, June 1997.
• 8 Douglas C. Schmidt. Middleware for real-time
  and embedded systems. Communications of the ACM,
  45(6), June 2002.
• 9 D. C. Schmidt, D. L. Levine, and S. Mungee.
  The design of the TAO real-time object request
  broker. Computer Communications, 21(4)294-324,
  April 1998.
• 10 Fabio Kon, Manuel Román, Ping Liu, Jina Mao,
  Tomonori Yamane, Luiz Claudio Magalhaes, and Roy
  H. Campbell. Monitoring, security, and dynamic
  configuration with the dynamicTAO reflective ORB.
  In Proceedings of the IFIP/ACM International
  Conference on Distributed Systems Platforms
  (Middleware 2000), New York, April 2000.
• 11 T. Fitzpatrick, G. Blair, G. Coulson, N.
  Davies, and P. Robin. Supporting adaptive
  multimedia applications through open bindings. In
  Proceedings of International Conference on
  Congurable Distributed Systems (ICCDS'98), May
  1998.
• 12 R. Koster. A Middleware Platform for
  Information Flows. PhD thesis, Department of
  Computer Science, University of Kaiserslautern,
  Germany, July 2002.
• 13 John A. Zinky, David E. Bakken, and Richard
  E. Schantz. Architectural support for quality of
  service for CORBA objects. Theory and Practice of
  Object Systems, 3(1), 1997.
• 14 Nalini Venkatasubramanian, CompOSEQ A QoS
  enabaled Customizable Middleware Framework for
  Distributed Computing., Distributed Middleware
  Workshop, Proceedings of the IEEE Intl.
  Conference on Distributed Computing Systems
  (ICDCS '99), June 1999.

Overview
Motivation
Background
Key Paradigms
Taxonomy
Examples
Conclusion
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Overview
Motivation
Background
Key Paradigms
Taxonomy
Thank you!
Examples
Conclusion