Loose Interface Definition: An Extended Interface Definition for Dynamic Service Composition

The concept of Dynamic Service Composition is to create a complex composite service through combining multiple software or hardware components at runtime. Dynamic Service Composition is similar to object-oriented or component-based software design approach since in both approaches an application is built as a combination of multiple components. However, in Dynamic Service Composition, an application is composed dynamically and autonomously by discovering, selecting, combining and organizing multiple components at runtime, whereas in the traditional object-oriented approach the component selection and organization are carried out by application designers at the implementation phase. This dynamic composition feature of Dynamic Service Composition provides flexibility and adaptability to applications. For example, an application built on top of the Dynamic Service Composition system is able to change its user interface dynamically according to user’s preference (e.g. English/Japanese menu, colorful/simple buttons etc.) or hardware configuration (e.g. low resolution for PDA, high resolution for PC) by permutating its user interface components. In the Dynamic Service Composition system, it is also possible to modify functionality or performance of an application to adapt various resource constraints or configurations (CPU speed, network bandwidth etc) by selecting optimum components and organizing them properly. Furthermore, a totally new application may emerge by combining several components designed for entirely different purposes. The Dynamic Service Composition system must be intelligent enough to be able to find an optimal solution of composing a logical, useful and functional application that satisfies given requirements under various conditions and limitations. It must also be autonomous so that an application could be composed with minimal user inputs. Several research projects have recently been done to realize such architecture. In this paper, we propose Loose Interface Definition, a set of techniques for defining interfaces of components. Loose Interface Definition maximizes the possibility that two different and independent components can communicate with each other. In the rest of this paper, we first explain how interface definition is used in Dynamic Service Composition. Next, we illustrate the problems of using existing Interface Definition Languages in Dynamic Service Composition. Then, we introduce Loose Interface Definition, explain its importance in Dynamic Service Composition, and prove its effectiveness onto the existing Web Service. Lastly, we propose XML Schema to describe Loose Interface Definition.