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3. Data model design
The first stage in the design of a data model is the designing of a conceptual data model. A conceptual data model is a representation of the data to be included in the system and how it relates to each other. It can be viewed as just an idea of how the data is to be modelled in the system. It is a model that is independent of any software to be used for implementation and how the data will be stored in the computer (Laurini et al 1996).

The entity-relational model has become the most popular approach for representing conceptual data models and it will be adopted for use in this paper (Worboys 1995). An entity is a thing that can be uniquely identified, for example a specific car or a specific person. Entities can be grouped into classes of similar objects known as entity types. A relationship is an association among entities or entity types (Chen 1976). The notation to be adopted in this paper for representing these entities and relations is illustrated in Figure 1 below.

Reads
Forward: A person must have one car
Backwards: A car may be owned by one or more people

Figure 1: The entity-relational diagramming notation
3.1. The conceptual data model
Figure 2 below illustrates the conceptual data model for representing ride check survey data in a GIS.

Figure 2: The conceptual data model
The five entity types illustrated in Figure 2 above are road, public transport route, trip path, stop and trip. A road represents the network that is used daily by different modes of transport. A public transport route is a physical feature representing a path taken by a public transport vehicle travelling along the transport network.

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