Virtual digital libraries

Digital libraries represent the meeting places for knowledge providers and knowledge consumers supporting and enhancing the process through which knowledge is created, used, and discovered. The demand for digital libraries is worldwide strong. These complex systems can offer a richer set of functionality than that initially expected and are able to transform the way in which joint research is conducted, thus responding to the requirements of a great number of research communities. In fact, nowadays research is a collaborative and multidisciplinary effort conducted by virtual research organisations whose components are spread worldwide. Despite this large and innovative demand the current digital library development models remain unchanged and so they are not able to match the emerging requirements. In this dissertation we propose a novel approach based on virtual digital libraries, i. e. digital libraries built by dynamically aggregating and appropriately presenting the pool of shared resources needed to fulfil the requirements of digital library communities. To support such an approach we introduced (i ) a reference model for understanding significant relationships among the components of digital libraries and for developing consistent services that support them and (ii ) a set of approaches and services able to provide virtual views over the heterogeneous information space resulting from reusing shared information sources. In particular, three approaches to information space virtualization are presented that provide profitable usage of the shared resources: information objects virtualization, collections virtualization, and distributed semantic search