Monday, March 16, 2009

Rapid Semantic Web Application Development with TopBraid Ensemble

TopQuadrant's product family, called TopBraid Suite, consists of the semantic modeling tool TopBraid Composer, a semantic server called TopBraid Live, and a client-side framework called TopBraid Ensemble. In the new Composer 3.0.0 beta 2 release we have finally aligned all these products into a single development and testing environment: When you download the Maestro edition of beta 2, you also get a personal edition of TopBraid Ensemble, ready to use without further download or installation needs!

Let me show you how this works in practice. Launch TBC-ME 3.0.0 beta 2, and open a web browser. Then go to the URL http://localhost:8083/tbl. The following screen will show up:

The TopBraid Ensemble team has put great efforts into refactoring and generalizing the Ensemble framework, so that it is now a comprehensive development framework for dynamic business applications. Ensemble applications consist of configurable rich-client components such as trees, forms and graphs (all based on Adobe Flex). These components can be re-arranged and re-wired in many ways, to customize an application's appearance and behavior for specific needs.

A freshly installed Ensemble comes with a default application that contains a pre-defined configuration of all built-in components. You can select this default application and run it on any RDF/OWL model from your workspace. The following screen shows the default Ensemble application on the geotravel.owl example ontology:

Ensemble is entirely driven by RDF/OWL models. Not only are the user interface components such as trees and forms driven by the underlying ontology, but the state of the whole application is represented by a flexible RDF-based data model. For example, if the selection of the Tree component (on the left) changes, then some RDF triples in the application's data model will change. Other components can react on those changes, and update their own internal state. If the selection of the tree changes, then the Results Grid (upper right) will display the instances of the selected class. This behavior is "soft-coded" though, and can be changed with a few mouse clicks. Below is a screenshot of a configuration dialog that can be used to customize and re-wire the components:

As shown above, it is possible to change certain properties for each component. For example, the root object and the transitive property of the tree component can be changed dynamically. Similarly, components can listen to events or publish events for other components to consume. This makes it very easy to create custom applications, for example, an application that displays a hierarchy of SKOS terms using the skos:broader property instead of a class tree. Needless to say, various user interface settings such as the choice of available buttons and style sheets are configurable as well. Any end-user with sufficient privileges can make those adjustments and then only needs to press the Save Application button to store this configuration and share it with her co-workers.

Like the rest of the TopBraid Suite, Ensemble is currently in beta stage and is very much work in progress. Now that the generic architecture and framework have been implemented, the team will focus on fleshing out the many details to make each component as flexible, powerful and visually appealing as possible. Expect significant improvements over the next few months - your feedback is appreciated in the meantime. Yet, our customers are not limited to the built-in components. We do provide a documented client-side API that allows anyone to add new Flex/ActionScript components. Furthermore, it is possible to drive parts of the application using server-side SPARQLMotion scripts.

Using Ensemble as the foundation for custom rich internet applications means that you can re-use large chunks of client-side components as well as server-side infrastructure. This infrastructure is well aligned with Composer and its features, such as the various database back-ends. Instead of re-inventing the wheel, you can focus on building the ontologies for your particular domain, and put them to work in your team.


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