Question

Q1) Discover ambiguities or omissions in the following statement of requirements for part of a Automated beverage serving system: An automated beverage serving system sells several beverages. Users select the type of beverage and input a credit card and a personal identification number. The beverage served and a user’s credit card account is charged. When the user presses the start button, a menu display of several beverages to choose from, along with a message to the user to select one type of beverage. Once a beverage has been selected, users are requested to input their credit card. Its validity is checked and the user is then requested to input a personal identifier. When the credit transaction has been validated, the beverage is served. Ambiguities and omission in the statement: 1. What would happen if the user enters an invalid card. 2. Q2) Rewrite the above description using the structured approach described in this chapter. Resolve the identified ambiguities in an appropriate way Q3) Write a set of non-functional requirements for the beverage serving system, setting out its expected reliability and response time. Q4) Identify and briefly describe four types of requirement that may be defined for a computer-based system

Answer 1

Ambiguities and Omissions Includes:

• Can a customer cancel a request if a mistake has been made?
• Can a customer buy several beverage of same kind / different kind or whether one at a time?
• What will be the response of the system if an invalid card in input?
• If a user enter the credit card before selecting the beverage, then what happens?
• Whether the user must press start button again to get a beverage?

Q.3)Possible non-functional requirements for the beverage serving system include:

1. Between 0600 and 2300 in any one day, the total system down time should not exceed 5 minutes.
2. Between 0600 and 2300 in any one day, the recovery time after a system failure should not exceed 2 minutes.
3. Between 2300 and 0600 in any one day, the total system down time should not exceed 20 minutes.

All these are availability requirements – note that these vary according to the time of day. Failures when most people are Ordering beverage are less acceptable than failures when there are few customers.

4. After the customer presses a button on the machine, the display should be updated within 0.5 seconds.
5. The beverage serving time after credit card validation has been received should not exceed 10 seconds.
6. When validating credit cards, the display should provide a status message for customers indicating that activity is taking place.

This tells the customer that the potentially time consuming activity of validation is still in progress and that the system has not simply failed.

Q.4) Methods to gather information and analyze requirement:

1. Observation

• Read documents and discuss with users
• Follow users to learn and identify the flow of their work that is to be automated; can also ask the user to explain why she/he did the job that way

2. Interviewing

• Conduct series of interview

3. Brainstorming

• Appoint an experienced moderator
• Do the session

4. Prototyping

• Paper prototype; draw pictures and/or figures to show sequence of the system/system flow
• Most common; mock-up system user interface, no need to perform calculation. May also prototype a particular aspect of the system

5. Use case analysis

hope this will help,