Towards a Federation of Government Metadata Repositories Gofran Shukair 1 , Nikos Loutas 1,4 , Vassilios Peristeras 2 , Klaus Reichling 3 , Fadi Maali 1 , Konstantinos Tarabanis 4 1 Digital Enterprise Research Institute, NUI Galway {firstname.lastname}@deri.org 2 EC, DG for Informatics, Interoperability Solutions for European Public Administrations vassilios.peristeras@ec.europa.eu 3 ]init[AG für Digitale Kommunikation, Berlin, Germany klaus.reichling@init.de 4 Information Systems Lab, University of Macedonia, Thessaloniki, Greece kat@uom.gr Abstract. Data models, taxonomies, ontologies, code lists and semantic data exchange formats are the key resources for achieving data interoperability. These resources exist in several national repositories that differ both in scope and in the target groups they address. They are implemented using different technologies and expose different interfaces to the end user. However the semantic content they include can often be reused even bypass the domain they were originally designed for. A standardized model that allows precise and rich description of repositories content is a key enabler of seamless data exchange. Such a model enables building a federation of repositories where users can search for resources or assets across all the available repositories using a unified user interface. Keywords: E-government, Semantic Interoperability, Data Exchange, federation, Cross-repository Querying. 1 Introduction Resources, such as data models, schemata, taxonomies, ontologies and code lists are the means for seamless data exchange. In the context of this work, we use the term asset to refer to these types of resources. Hence, an asset is a container dedicated to group artifact types. It can be considered as collection of data or a dataset. Currently assets exist in isolated national e-government metadata repositories. These repositories differ (i) in scope, (ii) in target group they address, (iii) in their underlying implementation technologies (iv) in interfaces they expose to the end user. The semantic content they include can often be reused even bypass the domain they were originally designed for. But the physical isolation of these repositories and the heterogeneity of the assets hamper the reusability of common concepts and cross- repository search. The creation of a common metadata schema for these assets allows smooth data exchange and integration between different repositories. This enhances the