reflactive middleware

5/20/2018 Reflactive Middleware

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Slide 1

Reflective middleware


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Slide 2

Table of content

Introduction:

What is a Middleware

Reflection and Reflective middleware

OpenORB

Dynamic TAO


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Middleware is a term that refers to a set of services

that reside between the applicationand the operating

system and aim to facilitate the development of

distributed applications

The main function of middleware is to mask the

inherent heterogeneity of distributed systems and

provide a standard set of interfaces and serviceswhich distributed applications can assume present

in any participating language, operating system or

machine environment.

What is a Middleware


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"Reflective techniques make it possible to open up

a language's implementation without revealing

unnecessary implementation details or

compromising portability".

Its able to inspect and change itself during the

execution time.

Reflection


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Reflection refers to the capability of a system to reason about

and act upon itself.

Reflective middleware is simply a middleware system thatprovides inspect ionand adaptat ionof its behaviour through an

appropriate CCSR (Causally Connected Self Representation).

Reflection and Reflective Middleware


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i) Inspect ion

Reflection can be used to inspect the internal behaviour of a

language or system. By exposing the underlying implementation, it

becomes straightforward to insert additional behaviour to monitor

the implementation.

ii) Adaptat ion

Reflection can also be used to adapt the internal behaviour of a

language or system. This can either be achieved by changing the

interpretation of an existing feature (by modification or

replacement) or by adding new features.

Inspection and Adaptation


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Reflection makes the middleware more adaptableto

its environment and better able to cope with change

Why Should a Middleware beReflective?


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Meta-level and Reification

Meta space contains two models:

1- metaspace model for structural reflection content and structure

2- metaspace model for behavioral reflection - activity


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Dynamic TAO


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i) The compositional meta-model provides access to

the object in terms of its constituent (base-level)

objects, represented as an object graph, in which the

constituent objects are connected together by efficient

primitive bindings referred to as local bindings.

ii) The encapsulation meta-model provides access to

the representation of a particular interface in terms of

its set of methods and associated attributes, together

with key properties of the interface including its

inheritance structure.

iii) The environment meta-model represents the execution environment for each interface as

traditionally provided by the middleware platform. In a distributed environment, this

corresponds to functions such as message arrival, enqueing, selection, dispatching,unmarshalling, thread creation and scheduling (plus the equivalent on the sending side)

In each case, a meta-object protocol (MOP) is defined to

inspect and adapt the respective meta-models.

OpenORB


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UbiDev vs Reflective Middleware

UbiDev approach:

- Adaptation is reactive according to changes in environment.

- Application cognitive model invariant.

Reflective Middleware approach:- Application can manipulate the middleware to adapt changes.

- Application is aware of the structure of the middleware.

- According to the model of the meta-level, application can

inspect and change the middleware behavior.

Same level of translucency.

In UbiDev the fine-grained control is expressed by the ontology

(leafs).

reflactive middleware

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