Blue Skies Airline, Drawing data flow diagrams from the given situation.
Reservation System

Blue Skies Airline, a fairly new airline, offers services between any two of the following cities:
Denver, Washington D.C., Los Angeles, New York City, Atlanta, and Cleveland. When a customer calls Blue Skies to make a flight reservation, the reservation agent first asks them for:
1. the desired travel dates,
2. the departure and destination cities, and
3. the seat grade desired (first class, business class, or economy).

The reservation agent then informs the customer of all available flights that meet their criteria; for each flight, the flight number, departure date and time, arrival date and time, and roundtrip price are communicated to the customer. If the customer finds any of the available flights acceptable, they may either pay for the ticket via credit card, or may request that the seat be held for 24 hours.

A limited number of seats on each flight are earmarked as frequent flyer seats. A customer who is a frequent flyer member may reserve and 'pay for' one of these seats by giving the agent their frequent flyer membership number; the agent then verifies that the appropriate balance is available in their account before the seat can be confirmed, at which point those miles are deducted from the account. (Note: therefore, the seat availabilities for regular customers and frequent flyers are different.)

The customer has two ticketing options: they may request that a conventional `paper' ticket be issued and mailed to their home address, or an electronic ticket (E-ticket) may instead be assigned, in which case the customer is simply informed of the E-ticket serial number by telephone.

Other simplifying assumptions:
1. Assume that all flights are round-trip between two cities (no three-legged itineraries are permitted.)

2. Disregard the complication that airlines sometimes have to switch aircrafts at the last minute due to mechanical difficulties, thus disrupting the seating assignments.

To help you draw the diagrams, the entities and their attributes are:
CUSTOMER(customer#, first name, last name, address)

FREQUENT FLYER(customer#, ®#, mileage balance)

FLIGHT(flight#, departure date, departure time, arrival date, arrival time, mileage)

SEAT(flight#, departure date, row, seat#, class, grade, status1)

TICKET(serial#, °ight#, departure date, row, seat#, customer#, type)

These entities are for your reference only. Your external entities, data stores, or classes do not need to conform all of these entities so that you have enough flexibility to design your own system.

Your tasks:

Please draw the data flow diagram by hand and document all the components. (external entities, data stores, processes, and data flows) in the DFDs.