The CORE project is an electronic library prototype that provides networked access to the full text and graphics content of American Chemical Society journals and associated Chemical Abstracts Service indexing since 1991. This project provides a full scale laboratory environment in which to explore issues of database structure, user interface capabilities, and information retrieval questions on a large, real-world scholarly electronic journal database. The magnitude of the CORE project, along with the complexities of searching and navigating large full-text collections require novel capabilities in user interface design. This report discusses key design issues and the capabilities of OCLC's XSCEPTER interface to the CORE database. It describes strategies for providing cross-platform interoperability, searching and browsing capabilities, and the formatting and display of complex SGML data.