The encyclopaedia of Iranian architectural history was established with the goal of increasing the accessibility of the widespread resources and documents related to Iranian architectural history and to provide a better and more productive space for collaboration of researchers and scholars, enabling them to expand and improve this encyclopaedia. The information architecture which started to get implemented is aimed to achieve three goals. First, increase the accessibility of the documents related to topics; second, the relation between concepts; third, the relation between concepts and documents. A three-layer architecture is designed to achieve the mentioned goals (EIAH cake). The underlying layer is a pool of information which is an integration of distributed digital repositories in our case. The top level is the knowledge representation level, an ontology of Iranian architectural history and the last layer which sits in the heart of this architecture is the mediator level which is responsible for establishing the relation between concepts and documents and enhancing search and semantic interoperability. The metadata model for describing resources in distributed digital repositories is customized based on Dublin Core with refinements. All documents in distributed repositories get their metadata according to this model and a detector agent (the mediator level) harvest metadata to interpret them by the ontology (the top layer). The results of this process will be presented in a semantic portal or might be used for complex search queries by end users. When this happens on a federation of distributed digital repositories, the ocean of separated documents becomes much meaningful and interpretable by human scholars.