Customization of On-line Services with Simultaneous Client-Specific Views

With the Internet success, a new trend has come up: online distributed services. Business companies (acting as client systems of these services) that are able to integrate such services effectively within their internal workflow will become leaders in their business markets. This however introduces the situation where multiple independent client systems are simultaneously accessing the same on-line service instance. This introduces a new research challenge concerning client-specific customization of an on-line service: different client systems may have different – possibly conflicting customization needs with respect to the functional and non-functional features of the on-line service. The problem with this is that all the different clientspecific views must be simultaneously imposed on the same distributed service instance; thus after the distributed service has become operational. We propose a dynamic customization model, Lasagne, that supports such client-specific combination of features at the instance level. In Lasagne a distributed service is structured as consisting of a minimal functional core – implemented as a component-based system, and an unbound set of potential extensions that can be selectively integrated within this core functionality. An extension to this core may be a new service, due to new requirements of end users. Another important category of extensions we consider, are non-functional services such as authentication, which typically introduce interaction refinements at the application level. Each extension is implemented as a layer of mixin-like wrappers. Wrappers are utterly useful for customizing on-line distributed services, since wrappers operate at the instance level, enabling runtime customization. The novelty of this work is that the composition logic, responsible for integrating extensions into the core system, is completely separated from the code of the core system, extensions and clients as well. Clients can customize this composition logic dynamically on a per client request basis by attaching extension identifiers to their interactions with the core system, enabling easyclient-specific customization.