Business enterprises today are increasingly being modeled as service-oriented enterprises (SOEs). That is, they are increasingly part of collaborations with other enterprises, with such collaborations being fulfilled by the exchange of business services among the participants. To that end, there is now a felt need for developing formal models of such collaborations, by leveraging past work on Enterprise Architecture (EA) models. In this paper, we present an architectural framework for modeling such collaborations as virtual enterprises (VEs), since these collaborations involve interactions among multiple enterprises. Our framework is modeled by treating the VE as an enterprise itself, but with special characteristics that distinguish it from regular enterprises, viz., nature of collaborations among the participating enterprises, extent of their participation, and conflicts among the participants. The latter characteristic arises due to the autonomy of the participants and the dynamic nature of inter-organizational business interactions, and is especially crucial for VE modeling. Throughout the paper, we illustrate our architectural framework with a realistic running example. We also present and discuss some future challenges regarding modeling dynamic behavior in the VE, in particular, conflict modeling & resolution among the participating enterprises.