The Situation Server is that part ofthe GCCS LES architecture and the Dynamic Multi-User Fusion System (DMIF) responsible for managing incomplete, uncertain, and unreliable situation data. It serves as a single point of access for situation information, identifies and values infonnation requirements, monitors for complex conditions of interest, and manages the distribution and viewing of information at geographically distributed sites. Within the GCCS LES architecture, the C31 Schema classes defme the language that architecturally compliant applications use to share information. Among the classes defmed within the C31 schema are those for entities, organizations, material, plans, intelligence, communications, situations. The C31 classes for situations represent the types, locations, capabilities, activities, and objectives of adversary forces. A DARPA-sponsored Object Management Working group (OMWG) is currently upgrading the C31 schema classes for representing situations and situation uncertainty. This representation must include all important possible interpretations of the data, must specify all relevant uncertainties, must link each interpretation to supporting and contradictory evidence, and must separately maintain specialized representations needed to support different fusion processes. In the design described in this paper, the situation classes are divided into two broad categories: those the describe the types of entities that may be in a situation, and those designed to represent uncertain beliefs about these entities.
Keywords: situation assessment, situation representation, uncertainty representation, information fusion