The Declarative Model

 This section describes the content of conceptual vocabularies and knowledge bases used for the particular case of the city of Turin.

 

Figure 8: Example of a Conceptual Vocabulary 

The conceptual vocabularies include common concepts shared by different knowledge bases. In this model, they include concepts about the characteristics of a line such as stops, exchange points, reserve areas and garages. For each concept, a generic description using the Concel language is formulated in terms of classes with sets of attributes and facets (e.g. allowed values for attributes, type of the attributes, etc). Then, this generic description is used to define the characteristics of each particular line as a set of instances of the previous classes. In this application, a total of 12 classes (with an total of 45 attributes) have been defined at generic. The domain model includes a total of 147 instances of such classes. Figure 8 shows a window of the KSM tool describing a conceptual vocabulary. The top half area shows part of the generic description of the stop class. The bottom part shows instances of such class.

 

Figure 9: Knowledge Bases for Classification and Prediction 

On the other hand, the generic model includes a total of 13 types of knowledge bases with several knowledge representations. The domain knowledge includes 32 knowledge bases (some generic areas are duplicated at domain level). Figure 9 shows an overview of the knowledge bases used for classification and prediction. The bases presented are: travel times, line model, scheduled behavior and problem types. Each base has its own knowledge representation. For instance, the problem types base uses rules to define classes of problems. In total, this set of knowledge bases include 50 components (rules for problems, tables for timetables, tables with temporal references for travel times, etc). Figure 7 shows a summary of the knowledge bases included in the planning knowledge. The figure shows 3 of the 18 planning knowledge bases: applicability conditions, plan refinement and subplan structures. In total, the planning knowledge includes 240 components.