The paper discusses some aspects of a project aimed at the development of a methodology and proper software tools for building academic digital libraries. A particular functional model of academic digital library has been proposed and analyzed. The emphasis of the presentation falls on some solutions of the large set of problems concerning the development of adequate mechanisms for semantics oriented search in multilingual digital libraries. An ontology-based approach is suggested in order to standardize the semantic annotation of the library resources and to facilitate the implementation of the functionality of the search engine. A proper subject ontology covering the area of Computer Science has been developed for this purpose. The paper discusses the requirements of the basic types of users of an academic digital library and suggests some relevant solutions.