substantially, but retain the grouping of perceptual, diagnostic, and inferential processes for modeling purposes. While this approach may be controversial in the research community (see, for example, the discussion by Flach, 1995), we believe it is appropriate for military simulation applications. We review several of the definitions and potential models proposed for situation awareness, discuss potential model implementation approaches, outline connections with other models discussed throughout this report, and present conclusions and goals for future development.
We should also note that considerable research remains to be done on defining, understanding, and quantifying situation awareness as necessary precursors to the eventual development of valid descriptive process models that accurately and reliably model human behavior in this arena. Because of the early stage of the research on situation awareness, much of the discussion that follows focuses on potential prescriptive (as opposed to descriptive) modeling approaches that may, in the longer term, prove to be valid representations of human situation assessment behavior. We believe this is an appropriate research and modeling approach to pursue until a broader behavioral database is developed, and proposed models can be validated (or discarded) on the basis of their descriptive accuracy.
Among the many different definitions for the term situation awareness (see Table 7.1), perhaps the most succinct is that of Endsley (1988:97):
Situation awareness is the perception of the elements in the environment within a volume of time and space, the comprehension of their meaning, and the projection of their status in the near future.
Each of the three hierarchical phases and primary components of this definition can be made more specific (Endsley, 1995):
Level 1 Situation Awareness—perception of the elements in the environment. This is the identification of the key elements or "events" that, in combination, serve to define the situation. This level tags key elements of the situation semantically for higher levels of abstraction in subsequent processing.
Level 2 Situation Awareness—comprehension of the current situation. This is the combination of level 1 events into a comprehensive holistic pattern, or tactical situation. This level serves to define the current status in operationally relevant terms in support of rapid decision making and action.
Level 3 Situation Awareness—projection of future status. This is the projection of the current situation into the future in an attempt to predict the evolution of the tactical situation. This level supports short-term planning and option evaluation when time permits.