Multi-stakeholder distributed systems (MSDSs), such as the Internet email and instant messaging systems, and e-business web service networks, raise new challenges for users, developers, and systems analysts. Traditional requirements engineering, validation, and debugging approaches cannot handle two primary problems of MS-DSs: the lack of consistent high level requirements and the ignorance problem caused by lack of communication among stakeholders. OpenModel addresses this ignorance problem: each MSDS node publishes a behavioral model of itself so that remote stakeholders can reason about their interactions with it. However, stakeholders will typically wish to hold back private state information, such as user identities and cryptographic keys. An OpenModel-based validation tool must tolerate missing information and yet still give useful analyses where possible. This paper overviews OMV, a novel approach to validation in the face of partial information based upon symbolic simulation of OpenModel models. We briefly illustrate our studies of the OMV tool in the domains of email and instant messaging.