WComp, a Middleware for Ubiquitous Computing

Ubiquitous computing relies on computers present everywhere, at any times and in any things. Indeed with recent years advance in mobile communication technologies and the miniaturization of computer hardware, processing units are becoming invisible and a part of the environment. Middlewares for ubiquitous computing have to manage three main features specific to their environment: devices’ mobility, devices’ heterogeneity and environment’s dynamicity. The devices’ mobility, due to motion of users and their associated devices, forbids to assume that entities are known and will always be available. The second concept, entity’s heterogeneity, outlines the diversity between devices’ capabilities and functionalities provided by new smart objects. Finally, the environment high dynamicity illustrates the ubiquitous world entropy with the appearance and disappearance of devices. Devices used to create applications are thus unknown before discovering them. Then, ubiquitous computing must deal with such a dynamic software environment (called software infrastructure afterwards). As a result, future ubiquitous computing architectures must take into account those three constraints to solve ubiquitous computing challenges. Our model of middlewareWComp is based on three parts: a software infrastructure, a service composition architecture, and a compositional adaptation mechanism. To manage the dynamicity and heterogeneity of entities in the software infrastructure, we highlight the use of Web Service Oriented Architecture for Device (WSOAD). This will be discussed in section 2. Ubiquitous applications are then based on a set of Web services for devices that must interact with each other. Consumers can not edit these services. Therefore, in order to add new functionalities to the system, an application has to be a composition of services for devices. Such an application, and thus such a composition, must be modifiable at runtime. The second part of the WComp middleware enables us to make such applications by dynamically composing services from the software infrastructure. To allow reusability of newly created functionalities, and for scalability purposes, such composition can be encapsulated as a composite service. This part of the system will be presented in Section 3. Moreover, the infrastructure of ubiquitous computing applications evolves dynamically led by appearances and disappearances of objects or devices. The variation of this infrastructure is dynamic due to arbitrary node mobility, failures or energy constraints. The service composition must be as relevant as possible according to the underlying software infrastructure. Managing these