1) Identify the main actors and 2) Draw a Use Case Diagram for a Phone/Voicemail System given the following constraints:

The main goal of the system is to act as a messaging service for an organization-wide telephone system. The organization may have several telephone numbers and multiple calls active at a given time.

The voicemail system gets activated after a callers dialed number to the telephone system goes unanswered for a given number of rings (e.g., five rings). The telephone numbers are uniquely mapped to mailbox numbers. Note that some numbers may not be assigned valid or active mailboxes (or none at all). Assume that the telephone system is responsible for functionalities such as establishing and managing the connection, managing the call (e.g., pickup, hang up), and providing information from and to the caller (e.g., the pressed phone keys, and obtain and play the actual voice message). An example of the interface to the phone system is given bellow (you may assume that all interface calls are blocking and as such the message system will wait until the interface call has completed execution and a value returned):

PhoneSystem

pickup() //Initiates one end of a connection

hangup() //Ends a connection

dial(char)//Allows dialing of 0..9,#, *

play(message)// Paly message

connection(): Boolean // True if a connection exists

record(int): message //Record a message until hangup() or time limit is reached

getRingCount(): int //Returns the number of rings

getDial(): char//Returns the character dialed (0 if buffer is empty else 1)

getExtension(): string //Returns the current extension

The voicemail system must support the callers to leave voicemails, and the mailbox owners to access and retrieve their voicemails. The owners can access and administer their mailbox with the following options:

Local access: from their own (local) phone devices via a hotkey on the phone device

Remote access: from other (remote) phones via dialing phone and/or extension number

Web or email access: via subscription

The caller can record a message verbally. The message is ended with a call hang up or a timeout in number of seconds. There is also an administration mailbox with extended functionality to manage the email system. This mailbox can access and manage other mailboxes (e.g., add or remove a mailbox and set a users password).