Help on my Use Case Diagram

[no steez]

Hey this is like my second attempt at a Use case.
I tried a pretty complicated one, and I am bound to have messed it up. Can anyone help me out?

link to image: http://i48.tinypic.com/9kw3ma.png



PROBLEM 4 - CAR HIRE SYSTEM
USE CASE 1 - MAKING RESERVATIONS
A customer contacts a reservation officer about a car rental.
The customer quotes the start and end dates needed, the preferred vehicle, and the pickup office.
The reservation officer looks up a prices file and quotes a price.
The customer agrees to the price.
The vehicle availability file is checked to see if an appropriate vehicle is available for the required time at the required office.
If the requested vehicle is available at the nominated pickup office, then it is reserved for the customer. An entry is made in the vehicle availability registering the reservation.
The reservation officer issues the customer is issued with a rental number.
A rental agreement is then created on the rental file, including the rental number, the rental period, the vehicle type and the pickup office.

[xlaiyn]

It looks like its coming together nicely to me. I hate Use Case diagrams. My class hasn't gone over how to put them together yet, so I'm teaching myself.

It looks like its coming along well, although I would probably move pieces around so it's slightly more organised and less clustered around the middle.

Also, where are these two pieces?

If the requested vehicle is available at the nominated pickup office, then it is reserved for the customer. An entry is made in the vehicle availability registering the reservation.

A rental agreement is then created on the rental file, including the rental number, the rental period, the vehicle type and the pickup office

And where is the arrow for this one? Shouldn't there be an arrow pointing from the reservation officer to this process?

The reservation officer issues the customer is issued with a rental number.

I'm hoping I'm somewhat helpful.

[aandrekun]

<<extends>> should only be used if there is an if statement

example:

The vehicle availability file is checked to see if an appropriate vehicle is available for the required time at the required office.

If the requested vehicle is available at the nominated pickup office, then it is reserved for the customer. An entry is made in the vehicle availability registering the reservation.

So the use case for 'Check vehicle availability file' would have an <<extend>> for the use case 'Register Reservation'  with a textbox saying {If vehicle is available} next to the <<extend>>

[Lasercookie]

This is probably how I'd go about creating this use case diagram.


It's not as detailed as the one you've done. I have combined some of the processes into one use case, mainly because it really isn't necessary to show all that nitty gritty information. If you can make something simpler without losing out on too much, then it's probably worth it - you can still understand how the system works from this one.

e.g. "A customer contacts a reservation officer about a car rental.
The customer quotes the start and end dates needed, the preferred vehicle, and the pickup office. " can be combined into 'Enquire about car rental'

and "The reservation officer looks up a prices file and quotes a price.
The customer agrees to the price. " can be combined into 'look up price list'.

Remember that the data flow in a use case diagram is always two way, so stuff like 'agrees to the price' I've really only shown implicitly. Use case diagrams don't focus on what kind of data you're actually communicating, but what the actual processes to carry out are. 

So as aandrekun has pointed out, you have been misusing extends.  It does look like you're treating use case diagrams as if you were drawing up a flow chart. The focus here are the actors interactions with the system. <<extends>> is basically an 'if statement' for use case diagrams. You do also have <<include>> available to you, which is pretty much 'if this is done, then always do this'.

I've also made use of arrow-heads. These don't imply one-way data flow, the data flow here is still two-way. They only indicate which actor is the one to initiate the process. The information we're given sometimes tells us if it's the customer that does this, or if it's the reservation officer that does this. i.e. the customer can't just start looking up the price list themselves, the reservation officer has to do that.

I'm not sure if I should have had 'create rental agreement' connecting to the customer too. Probably. The information didn't state it explicitly, so I didn't worry about it.

In terms of neatness, doing rough drafts on paper is usually helpful. If this was an exam question, drawing the diagram in pencil is probably the best option.