Currently there is a great deal of interest concerning polyinstantiation in database management systems (DBMSs). However, polyinstantiation is a specific solution to a problem faced by all secure systems, and the problem itself is not well characterized. The problem stems from the interference between subjects of different security compartments. The authors focus on this problem, which they call multiparty update conflict (MUC). They discuss and evaluate some solutions to the MUC problem, such as polyinstantiation and rigid classification. A framework for a class of MUC solutions based on polyinstantiation is described, and several intermediate solutions between rigid classification and polyinstantiation are enumerated.