In this paper we report the experience of using semantic based tools and technologies for (collaboratively) modeling administrative procedures and their related documents, organizational roles, and services, in the Italian Public Administration (PA), focusing in particular on the interoperability aspects faced during the modelling process. This experience, the reported lessons learned and next steps identified, highlight the potential and criticality of using web 2.0 semantic technologies and tools to enhance participatory knowledge sharing, interoperability, and collaboration in the modeling of complex domains in the PA.