1. GYTE - Bilgisayar Mühendisliği Bölümü Bilgisayar Mühendisliği Bölümü GYTE - Bilgisayar Mühendisliği Bölümü AN ARCHITECTURE FOR NEXT GENERATION MIDDLEWARE BIL 601 ADVANCED TOPICS IN OPERATING SYSTEMS DO Ğ U SIRT DECEMBER 2013

2. GYTE - Bilgisayar Mühendisliği Bölümü CONTENT Introduction Background On Reflection An Architecture for Reflective Middleware Experiments in Reflective Middleware Concluding Remarks 2

3. GYTE - Bilgisayar Mühendisliği Bölümü INTRODUCTION 3 The role of middleware is to present a unified programming model for coders. Also works for masking out problems of heterogenity and distribution. Standards should remain adaptive to new challenges ( multimedia, real time apps, mobility etc.) Such challenges require new approaches to be able to configure the underlying support. It is necessary for a system’s underlying components to be ready for inspection and adaptation at runtime.

4. GYTE - Bilgisayar Mühendisliği Bölümü INTRODUCTION 4 Current generation platforms Not configurable Black Box (details hidden) Propose an approach to the designing of configurable and open middleware platforms based on concept of reflection. Reflective architecture for next generation middleware platforms.

5. GYTE - Bilgisayar Mühendisliği Bölümü BACKGROUND ON REFLECTION Reflection Hypothesis “In as much as a computational process can be constructed to reason about an external world in virtue of comprising an ingredient process formally manipulating representations of that world so too a computational process could be made to reason about itself in virtue of comprising and ingredient process formally manipulating representations of its own operation an structures” (Smith 1982) 5

6. GYTE - Bilgisayar Mühendisliği Bölümü BACKGROUND ON REFLECTION A program can access, reason about and alter its own interpretation Access to the interpreter is provided through a meta object protocol(MOP) which defines services available at the meta level. Example: Operations available at the meta level include altering the semantics of message passing over a wireless link and inserting before or after method invocations. 6

7. GYTE - Bilgisayar Mühendisliği Bölümü BACKGROUND ON REFLECTION Open engineering It can be used for inspecting the internal behavior of a language or system. By exposing the underlying implementation, it becomes straightforward to insert additional behaviour to monitor the implementation. Although reflection is a promising technique, there are a number of potentional drawbacks of this approach. 7

8. GYTE - Bilgisayar Mühendisliği Bölümü AN ARCHITECTURE FOR REFLECTIVE MIDDLEWARE RM_ODP (Reference Model for Open Distributed Processing) Computational Model Objects can have multiple interfaces Operational stream and signal interfaces are supported. Explicit bindings can be created between compatible interfaces. Per Object Meta Space Each object various capacities for reflection Control over the support (problems of maintaining integrity are minimised due to the limited scope of the change) Meta object groups 8 General Principles

9. GYTE - Bilgisayar Mühendisliği Bölümü AN ARCHITECTURE FOR REFLECTIVE MIDDLEWARE 9 Procedural Approach Meta level exposes the actual program that implements the system. Casual connection(As the implementation itself directly manipulated). Meta-Space Models Closely related but distinct meta models. Seperation of concerns between different system aspects. composition(), encapsulation(), environment() operations. General Principles

10. GYTE - Bilgisayar Mühendisliği Bölümü AN ARCHITECTURE FOR REFLECTIVE MIDDLEWARE Objects can have multiple interfaces Each interface has an associated encapsulation and environment meta model. Compositional model is associated with the object itself and common to all interfaces. 10 DESIGN / The structure of the meta space

11. GYTE - Bilgisayar Mühendisliği Bölümü AN ARCHITECTURE FOR REFLECTIVE MIDDLEWARE 11 DESIGN

12. GYTE - Bilgisayar Mühendisliği Bölümü AN ARCHITECTURE FOR REFLECTIVE MIDDLEWARE Composition Access the object in terms of constituent objects Composition of object represented as an object graph,in which constituent objects are connected together Some objects in this graph can be binding objects,allowing distributed configurations to be created Encapsulation Provides access to the representations of a particular interface in terms of its sets of methods and associated attributes. Language Dependent 12 DESIGN

13. GYTE - Bilgisayar Mühendisliği Bölümü AN ARCHITECTURE FOR REFLECTIVE MIDDLEWARE DESIGN 13 Enviroment Represents the execution environment for each interfaces traditionally provided by the middleware platform. Functions such as message arrival, enqueing, selection dispatching, thread creation and scheduling.

14. GYTE - Bilgisayar Mühendisliği Bölümü AN ARCHITECTURE FOR REFLECTIVE MIDDLEWARE 14 Groups provide a uniform mechanism for invoking a set of interfaces. For example, groups can be used, at the base level, to multicast new share price information or at the meta level, to insert a new QoS monitoring method. DESIGN / Reflecting Groups

15. GYTE - Bilgisayar Mühendisliği Bölümü AN ARCHITECTURE FOR REFLECTIVE MIDDLEWARE Extensible library of components which can be configured to build middleware platforms Primitive Components Primitive Components Include A range of low level communications protocols, such as IP and IP multicast A range of end-system components buffers, threads A range of management policies. Scheduling policies, buffer allocation policies. 15 DESIGN / Component Framework

16. GYTE - Bilgisayar Mühendisliği Bölümü AN ARCHITECTURE FOR REFLECTIVE MIDDLEWARE 16 DESIGN / Component Framework Composite Components ( open library ) A range of transport binding supporting, stream and operational interaction. Pre configured environment meta-spaces offering access to buffering, dispatching.

17. GYTE - Bilgisayar Mühendisliği Bölümü AN ARCHITECTURE FOR REFLECTIVE MIDDLEWARE Reflective architecture provides strong design for future middleware platforms and offers principled and comprehensive access to the middleware platform. Proposing set of components which can be tailored to the needs of an application Configuration can be adapted at run time, should the initial environmental assumptions change. It minimizes problems of maintaining integrity. (Scoping where by every object in its own metaspace) Meta space is highly structured minimizing scope of changes 17 DISCUSSION

18. GYTE - Bilgisayar Mühendisliği Bölümü EXPERIMENTS IN REFLECTIVE MIDDLEWARE Adapt Project (Lancaster University and BT Labs) Open binding is an object which provides access to its compositional meta model. The use of binding object in graphs allows open binding to span multiple address spaces or multiple nodes. 18 Open Bindings

19. GYTE - Bilgisayar Mühendisliği Bölümü EXPERIMENTS IN REFLECTIVE MIDDLEWARE Test environment COOL-ORB, CORBA (Common Object Request Broker Architecture) implementation from Chorus Systems (Sun, Oracle) Laptops, PC’s Windows NT Switched Ethernet, Wavelan, GSM COOL-ORB support two comm, infrastructure TCP-IP CHORUS-IPC Ensemble (Orientation) Enables the programmers to select a particular protocol profile at bind time by providing list of component modules. Run time adaptation(Modification of modules and dynamic reconfiguration). 19 IMPLEMENTATION OF OPEN BINDINGS

20. GYTE - Bilgisayar Mühendisliği Bölümü EXPERIMENTS IN REFLECTIVE MIDDLEWARE For operational bindings Standart Corba bind call extended To enable the specification of the initial protocol graph To return an interface providing access to the meta- space Ensemble based operational bindings allow direct realisation of concept of reflective groups. 20 IMPLEMENTATION OF OPEN BINDINGS

21. GYTE - Bilgisayar Mühendisliği Bölümü CONCLUDING REMARKS Presented design for an next generation platforms. Exploits concept of reflection to provide the desired level of configurability and openness The most important features of design Associating meta space with every object-interface Subdivision metaspaces into three parts Consistent use of object graphs to represent composite components in the architecture Primitive and composite components 21

22. GYTE - Bilgisayar Mühendisliği Bölümü THANK YOU… 22