Data Dictionary
The Data dictionary was developed by using the methods outlined below.
1) First, the information used by the existing systems such as VICS and Variable Message Signs was checked and the data elements were extracted from these systems.
2) Second, the data elements were categorized according to the information classifications used by the ITS System architecture and a data model was constructed.
3) Finally, the data dictionary was expanded based on the data model so that they would correspond to the 20 individual systems expected to be deployed by the road administrator.
The illustration below shows what is called the general model. It shows the upper classification of the data model, or what would be called the upper class in an object oriented system.
As it is shown below, road related information is organized into two categories.The first category is the basic group, which is used by all systems involved.The second category is the specific application group, which is used by specific systems.
These upper classes all have corresponding lower classes. Together they constitute a multi-tiered structure.
The data element is the smallest unit of data and makes up the lowest class in the structure.
