To support mobile computing systems for first responders at mass casualty sites, as part of the WIISARD (Wireless Internet Information System for Medical Response in Disasters) project, we have developed a data architecture to gracefully handle an environment with frequent network failure and, multiple writers that also supports rapid dissemination of updates that could be critical to the safety of responders. This is accomplished by allowing for a subset of the overall information available in a disaster scene to be cached locally on a responder's device and locally modified with or without network access. When the network is available, the local subset of the model is automatically synchronized with a server that contains the full model, and conflicts are resolved. When changes from a device are committed, the changes are instantly sent to any connected devices where the local subset would be modified by the changes.