Semantic Knowledge Representations for Soft Data Fusion - Efficient Decision Support Systems: Practice and Challenges from Current to Future - page 6

3. Soft data fusion
3.1 Different levels of fusion
Many studies and systems exist that deal with data and information fusion. Each one of them
focuses on a specific part of fusion. A detailed description of a large number of fusion models
is proposed in Bosse et al. (2007). Within this section, we will focus on two of them. Our aim
is to explain the purpose of semantic and soft data fusion, in the wide context of data and
information fusion.
The North American Joint Directors of Laboratories (JDL) model for data fusion (see Hall &
Llinas (2001)) is the most popular. It was first proposed in 1985 by the US Joint Directors
of Laboratories Data Fusion group and revised over the years. The processing is divided
into five levels described in Figure 2. The JDL model was initially proposed for the military
applications but is now widely used in civil domains as well, such as business, medicine, etc.
Fig. 2. The JDL data fusion process model (1999 revision)
Through its different levels, the JDL model divides the processes according to the different
levels of abstraction of the data to be fused and the different problems for which data fusion
is applicable. The initial levels are the following ones:
Level 0: Estimation of States of Sub-Object Entities (e.g. signals, features)
Level 1: Estimation of States of Discrete Physical Objects (e.g. vehicles, buildings)
Level 2: Estimation of Relationships Among Entities (e.g. aggregates, cuing, intent, acting on)
Level 3: Estimation of Impacts (e.g. consequences of threat activities on assets and goals)
Level 4: Process Refinement Level was initially recognized within the 1999 version of the JDL,
but was then integrated to the Resource Management model levels and thus is not part of
the fusion process itself.
Endsley (1995) models the data fusion process from a human perspective (i.e., Mental Model).
The model has two main parts: the core Situation Awareness portion and the various factors
affecting Situation Awareness. The core portion depicts three levels of mental representation:
perception, comprehension and projection (see Figure 3):