Abstract E-commerce, web-based booking systems, and on-line auction systems are only a few examples that demonstrate how WWW sites are evolving from hypermedia information repositories to hypermedia distributed applications, hereafter web applications. They blend navigation and browsing capabilities, common features of hypermedia, with "classical" operations (or transactions), common features of traditional information systems. This new coupling, between hypermedia and operational features, raises a number of novel design issues. In this paper, we focus upon conceptual modeling for web applications, trying to identify its scope and its main issues. We claim that conceptual modeling for web applications is not just the union of two activities performed in isolation: modeling the operations and modeling the hypermedia. Rather, the integration of the two facets of design (hypermedia and operations) is the issue. The coexistence of operational and navigational aspects poses, amon...