Libraries, in their twofold function of collecting and safekeeping knowledge, are similar to Museum collections; they are in charge of maintaining, that is protecting, the integrity of their heritage (not only as an evidence of the activities of producers of each single document, but also as a memory support); of facilitating direct examination and research and, at last, of improving popularization and education. While the first two aspects are already matter of study and of huge efforts in order to suitably solve the general problem of cataloguing - just remember the 'EncylopZdie': perhaps the first example of hypertext -, the third is the most neglected, due to both the troubles associated to direct vision and the lacking of reliable tools. The aim of a virtual library is to put at users' disposition not only its catalogues, but also its 'objects', exhibited on a virtual desktop, for both the researcher and the hurried tourist urged by the following visitors and therefore unable of critical meditation. The aim of this paper is to show how the use of some technological standards recommended by the W3C may represent an adequate solution also to the needs of widespread fruition of the library as a part of the heritage, as long as tagging is guided by a deep analysis of the application and of its context performed by means of conceptual tools (like the E-R approach and heuristic rules from the IR field). Moreover XML-like technologies allow today to implement user Web interface comparable to those developed by proprietary tools, miming in a virtual space the most suitable metaphor, and offering a set of tools to manipulate objects directly on the browser.