Online services can be difficult to conceive and to manage due to their inherent complexity, involving many subjects with distinct goals (user, managers, public and private agencies, ...), often regulated by complex norms and procedures; moreover, they are frequently based on complex data and information structures usually coming from heterogeneous data sources (old paper archives, legacy systems, ...); finally, they must be delivered to users through multiple channels (in-person, by phone, by the Web, by kiosks, etc.). Conceptual models for Web applications can be very useful to manage this complexity, but a new level of integration is required to simultaneously deal with non-trivial processes, complex data structures and rich hypermedia communication patterns, under multiple constraints (legal, technical, ...). Digital Government is a major application domain for this topic. It aims at improving government-citizen interactions using information and communication technologies. Government agencies collect, store, process and share information about million of citizens who have different preferences, backgrounds and interaction requirements.The aim of this paper is to describe some real authors' experiences in adopting existing conceptual models to design and to implement advanced Digital Government applications and to deploy new online services. In particular, we discuss the learned lessons and the main issues we have run into modeling online fiscal services for Italian local agencies.