E-government refers to re-innovation process currently undergoing within the Public Administration which is defined as the use of Information and Communication Technologies to achieve better government. In particular Integrated Service Delivery, one of the most challenging area of e-government,refers to services that cross traditional administrative and functional boundaries in order to provide a unified and eased access to citizens. The essence of Integrated Service Delivery is to create seamless services that are citizen-centered by improving inter-agency collaboration and information sharing. This thesis concerns a model-driven design of eGovernment Service Marketplace for dynamic discovery and delivery of distributed public services. The aim of this research is to make a contribution to the following conceptual critical issues. The first issue concerns the design of a citizen-oriented system by taking into account also issues of interoperability, information sharing and legacy system integration across government agencies . The eGovernment Service Marketplace concept aims at proposing an innovative model of shared, interoperable and evolutionary services for citizens enabling and promoting inter-agency integration at different levels of technological sophistication. The second issue is the proposition of a multi-layered modeling approach for Information System formalization which combines advantages of both Conceptual and Semantic modeling techniques. The proposed Holistic modeling approach aims at addressing the needs of today's complex Information Systems operating in an open environment. The third issue concerns the design of a model for flexible discovery and management of heterogeneous resources. The proposed Distributed and Dynamic Service Discovery is a Grid-based model for service and service registry discovery in large-scale distributed environment.