One of the challenges of Grid computing is to handle changes in the execution environments, which are not predictable in systems composed of large number of distributed components on heterogeneous environments. For this reason, the system needs to be dynamically reconfigurable, and must exhibit autonomic properties.

Simple and deterministic dynamic reconfiguration is a real challenge in systems that contain hierarchical components that feature their own activities and that communicate asynchronously.

The autonomic computing paradigm is related to this challenge because is consists of building applications out of self-managed components. Components which are self-managed are able to monitor their environment and adapt to it by automatically optimizing and reconfiguring themselves. The resulting systems are autonomous and automatically fulfill the needs of the users, but the complexity of adaptation is hidden to them. Autonomicity of components represents a key asset for large scale distributed computing. We are also

Encapsulation properties, components with configurable activities, and system description in ADL files provide safe basis for model checking of component systems.

For instance:

The Vercors platform investigates such kinds of scenarii.

Distributed computational applications are designed by defining a functional or do- main decomposition, and these decompositions often present structural similarities (master-slave, 2D-Grid, pipeline etc.).

In order to facilitate the design of complex systems with large number of entities and recurring similar configurations, we plan to propose a mechanism for defining parameterizable assembly patterns in the Fractal ADL, particularly for systems that contain parameterized numbers of identical components.

Another area of investigation is the tools for configuring, deploying and monitoring distributed component systems.

Because component based programming is somewhat analogous to the assembly of building blocks into a functional product, graphical tools are well suited for the design and monitoring of component based systems. The Fractal community actually proposes such a tool: the Fractal GUI. We have extended this tool to evaluate the feasibility of a full-fledge graphical interface for the design and monitoring of distributed components. The result is available within the IC2D GUI, you can try it out, but consider it as a product in alpha state. Development is indeed currently discontinued as we are waiting for a new release of the Fractal GUI, and some features are only partially implemented (runtime monitoring, composition of virtual nodes).

The GUI allows the creation of ADL files representing component systems, and - the other way around - also allows to load ADL files and get a visual representation of systems described in the ADL files. We have worked on the manipulation of virtual nodes - a deployment abstraction -: components display the virtual nodes where they are deployed, and it is also possible to compose virtual nodes

Ultimately, we would like to couple the visualization of components at runtime (currently unavailable here) with the standard monitoring capabilities of IC2D: we would get a structural view of the application in the Fractal GUI, and a topological view in the standard IC2D.

34.4.1. Howto use it

If you want to try out the extended Fractal GUI for ProActive (for versions of ProActive < 3.2):

• start IC2D

• Components --> start components GUI

• to load an ADL file:

  1. File --> Storage --> select the storage repository which is the root repository of your ADL files. For example you can select the 'src' directory of the ProActive distribution

  2. File --> Open --> select an ADL file in the storage repository. For example you can select the 'helloworld-distributed-wrappers.fractal' file in the src/org/objectweb/proactive/examples/components/helloworld directory of the ProActive distribution.

• to modify an ADL file, you can use the Graph tab for a structural view, while the Dialog tab gives you access to the properties of the components, including the composition of the virtual ndoes.

• to save an ADL file: File --> Save

	Note
	Since version 3.2 the experimental GUI in IC2D is not functional anymore. Developments are discontinued as we are moving towards an eclipse plugin integrated with the new eclipse-plugin-based version of IC2D. A proposal specification for this new GUI is available here. We intend add extension for Grid-specific features (control of deployment, visual abstractions etc.)

Other areas of research that we are opening around this work include:

Some features of the Fractal model are not implemented: