Read the following case study for a brief description of a taxi company called Fast Cabs. Each office has a manager, several taxi owners, drivers and administrative staff. The manager is responsible for the day-to-day running of the office. An owner provides one or more taxis to Fast Cabs and each taxi is allocated for use to a number of drivers. The majority of owners are also drivers. Fast Cabs taxis are not available for hire by the public hailing a taxi in the street but must be requested by first phoning the company to attend a given address. There are two kinds of clients, namely private and business. The business provided by private clients is on an ad hoc basis. The details of private clients are collected on the first booking of a taxi. However, the business provided by business clients is more formal and involves agreeing a contract of work with the business. A contract stipulates the number of jobs that Fast Cabs will undertake for a fixed fee. When a job comes into Fast Cabs the name, phone number and contract number (when appropriate) of the client is taken and then the pick-up date/time and pick-up/drop-off addresses are noted. Each job is allocated a unique job ID. The nearest driver to the pick-up address is called by radio and is informed of the details of the job. When a job is completed, the driver should note the mileage used and the charge made (for private clients only). If a job is not complete, the reason for the failed job should be noted.
(a) Identify the main entities of Fast Cabs.
(b) Identify the main relationships between the entities.
(c) Determine the multiplicity constraints for each relationship.
(d) Identify attributes and associate them with an entity or relationship.
(e) Determine candidate and primary key attributes for each entity.
(f) Using your answers (a) to (e) represent the data requirements of the Fast Cabs as an enhanced ER (EER) model. (Hint: Use optional Step 1.6 of the methodology to identify private clients (subclass) and business clients (subclass) as being special types of clients (super class).) State any assumptions necessary to support your design.