Aspect Oriented Programming

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SEA Side Software Engineering Annotations

• AAnnotation 9 AOP
• One hour presentation to inform you of new
  techniques and practices in software development.
  
• Professor Sara Stoecklin
• Director of Software Engineering- Panama City
• Florida State University Computer Science
• sstoecklin_at_mail.pc.fsu.edu
• stoeckli_at_cs.fsu.edu
• 850-522-2091
• 850-522-2023 Ex 182

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Adaptive Oriented Programming
Dr. Sara Stoecklin Florida State University
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Adaptive Oriented Programming

• MIT Technology Review
• January/February 2001 issue defined ten emerging
  areas of technology that will soon have a
  PROFOUND impact on the economy and on how we live
  and work.
• They listed as one of those ten areas adaptive
  programming.

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Adaptive Oriented Programming

• Alias
• Adaptive Oriented Programming (Northwestern
  University)
• Subject Oriented Programming (IBM)
• Aspect Oriented Programming (XEROX)

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Adaptive Oriented Programming

• Definition
• A technique for creating robustness to changes in
  a particular aspect of a system, program, or
  software component.

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Adaptive Oriented Programming

• Concept
• Design software iteratively, identifying those
  things that will become necessary to change at
  later dates.
• Build abstractions for these changes so that
  changes during maintenance will be necessary only
  in parts of the system.

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Adaptive Oriented Programming

• Concept
• Software is written in a manner that allows the
  programmer to work at a higher level of
  abstractions than the normal executable code.
• It can be implemented as meta programming.

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Adaptive Oriented Programming

• Concept
• Adaptive Programming is an extension of OO
  software development where relationships between
  functions and data are flexible or loosely
  coupled.

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Aspect Oriented Programming
Agenda

• Why Aspect Oriented Programming?
• What are Aspects?
• What is a cross-cutting with Aspects?
• How AOP tackle a software problem?
• Examples.
• Conclusions

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Aspect Oriented Programming
Why Aspect Oriented Programming?

• A typical process model.
• Divide system into small units of functionality.
• Write code for each functional unit.
• Have the units collaborate to form the system.
• Design decisions are tangled, business rules are
  tangled.
• Results in tangled code.

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Aspect Oriented Programming
Why Aspect Oriented Programming --Contd.

• Hard to manage, maintain and expand.
• OO and Procedural languages have a few points in
  common, functional decomposition into
  procedure/function/object.
• Called GP(Generalized Procedure Languages).
• The Tangling problem is not solved by GPs.

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Aspect Oriented Programming
What is a Cross Cutting with Aspects?
SOFTWARE PROJECT
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Aspect Oriented Programming
What is a Cross Cut?
SOFTWARE PROJECT
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Aspect Oriented Programming
What is an Aspect?

• Its not a unit of systems functional
  decomposition.
• Its a property that effect the performance of
  the components in the system.
• e.g. synchronization, memory access patterns etc.
  

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Aspect Oriented Programming
How AOP addresses the problem.

• A new technique called AOP.
• Aspects and concerns can be dealt with in a
  relatively new way.
• Provides appropriate isolation between the
  components and the aspects.

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Aspect Oriented Programming
Proposed Solution

• AOP is a step ahead in this direction of
  separation of concern.
• Allows to write a separate code block for a
  design decision instead of spreading it all over.
• Aspect Oriented Languages
• AspectJ (core functionality),
• Cool(synchronization) and
• Ridl( distribution concerns).

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Aspect Oriented Programming
An Example
Suppose you have an order entry system and one
use case allows you to create and cancel orders.
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Aspect Oriented Programming
Order Entry System

• Lets assume we have the following simplified
  Order class as our base object
• public class Order
• int orderID
• public void placeOrder()
• public void cancelOrder()

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Aspect Oriented Programming
Order Entry System

• Suppose we now need to add authorization checks
  for the persons entering and canceling orders.
• Suppose also we would like to check in particular
  if the requester has access rights to the methods
  placeOrder() and cancelOrder().

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Aspect Oriented Programming
Order Entry System

• If we have written this in an OO architecture
  with something like EJB. Then we are stuck with
  the strict OO implementation of EJB.
• EJB separates the services from the business
  objects BUT now we want to add a service to the
  already written C/S service (i.e EJB services)
  and messaging provided in both Java and EJB

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Aspect Oriented Programming
Order Entry System

• Thus this access to user procedures may be an
  ASPECT of C/S systems.

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Aspect Oriented Programming
The Difference

• In OO, components are glued together with bits of
  code using create this object, create that
  object, etc.
• A transaction processing goes something along
  these lines log this method to a file for
  debugging, run a security check, start a
  transaction, open a database connection, remember
  to catch exceptions or Win32 structured
  exceptions and validate parameters.
• Thus this code is duplicated across transactions
  for transaction and session management.

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Aspect Oriented Programming
The Difference

• In the realm of AOP, these aspects need to be
  programmed separately.
• Aspects associated with components often use
  metadata such as the session management aspect or
  data management aspect or transaction management
  aspect.

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Aspect Oriented Programming
The Difference

• The runtime uses the metadata to compose the
  stack of aspects, typically occurs at object
  creation time.
• Thus the correct class is created according to
  the aspect technique (CICS like transaction
  management)

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Aspect Oriented Programming
What are some main uses?
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Aspect Oriented Programming
What are some main uses?
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Aspect Oriented Programming
What are some main uses?
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Aspect Oriented Programming
Related work

• Mehmet Aksit et al. at university of Twente
  developed composition filters,object model.
• Component language is OOP.
• Aspects used to synchronization and
  communication.
• Calton Pu et. Al. at Oregon Graduate institute,
  OS kernels. Components are typical OS kernels,
  aspects are optimizations based on invariants.

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Aspect Oriented Programming
Related work

• Karl Lieberherr et al at north eastern university
  trying to make OOP more reusable by introducing
  aspects to control cross cutting issues.
• Joe Yoder has made progress Reflection and
  Meta-object Proposals
• Subjective Programming introduced by IBM
• Other Engineering Disciplines
• Mechanical engineers use static, dynamic and
  thermal models as these models cross cut each
  other.

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Aspect Oriented Programming
Conclusions

• Components are properties of a system for which
  implementation can be easily encapsulated in a
  procedure/function/object.
• Aspects are properties for which implementation
  cant be encapsulated.
• Aspects cross-cut in systems implementation.
• AOP is needed for clean abstraction and
  composition of both components and aspects.

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Aspect Oriented Programming
Conclusions

• AOP is different from other languages as it
  provides separate languages for component and
  aspects.
• Also provides different abstraction and
  composition mechanisms.
• Aspect weaver is used to co-ordinate them.
• These systems are proven to be easier to develop
  and maintain and being more efficient too.